rfc9578.original   rfc9578.txt 
Network Working Group S. Celi Internet Engineering Task Force (IETF) S. Celi
Internet-Draft A. Davidson Request for Comments: 9578 A. Davidson
Intended status: Standards Track Brave Software Category: Standards Track Brave Software
Expires: 5 April 2024 S. Valdez ISSN: 2070-1721 S. Valdez
Google LLC Google LLC
C. A. Wood C. A. Wood
Cloudflare Cloudflare
3 October 2023 May 2024
Privacy Pass Issuance Protocol Privacy Pass Issuance Protocol
draft-ietf-privacypass-protocol-16
Abstract Abstract
This document specifies two variants of the two-message issuance This document specifies two variants of the two-message issuance
protocol for Privacy Pass tokens: one that produces tokens that are protocol for Privacy Pass tokens: one that produces tokens that are
privately verifiable using the issuance private key, and another that privately verifiable using the issuance private key and one that
produces tokens that are publicly verifiable using the issuance produces tokens that are publicly verifiable using the issuance
public key. public key.
Status of This Memo Status of This Memo
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and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/rfc9578.
Copyright Notice Copyright Notice
Copyright (c) 2023 IETF Trust and the persons identified as the Copyright (c) 2024 IETF Trust and the persons identified as the
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology
3. Protocol Overview . . . . . . . . . . . . . . . . . . . . . . 3 3. Protocol Overview
4. Configuration . . . . . . . . . . . . . . . . . . . . . . . . 4 4. Configuration
5. Issuance Protocol for Privately Verifiable Tokens . . . . . . 8 5. Issuance Protocol for Privately Verifiable Tokens
5.1. Client-to-Issuer Request . . . . . . . . . . . . . . . . 9 5.1. Client-to-Issuer Request
5.2. Issuer-to-Client Response . . . . . . . . . . . . . . . . 10 5.2. Issuer-to-Client Response
5.3. Finalization . . . . . . . . . . . . . . . . . . . . . . 11 5.3. Finalization
5.4. Token Verification . . . . . . . . . . . . . . . . . . . 12 5.4. Token Verification
5.5. Issuer Configuration . . . . . . . . . . . . . . . . . . 12 5.5. Issuer Configuration
6. Issuance Protocol for Publicly Verifiable Tokens . . . . . . 13 6. Issuance Protocol for Publicly Verifiable Tokens
6.1. Client-to-Issuer Request . . . . . . . . . . . . . . . . 14 6.1. Client-to-Issuer Request
6.2. Issuer-to-Client Response . . . . . . . . . . . . . . . . 15 6.2. Issuer-to-Client Response
6.3. Finalization . . . . . . . . . . . . . . . . . . . . . . 16 6.3. Finalization
6.4. Token Verification . . . . . . . . . . . . . . . . . . . 16 6.4. Token Verification
6.5. Issuer Configuration . . . . . . . . . . . . . . . . . . 17 6.5. Issuer Configuration
7. Security considerations . . . . . . . . . . . . . . . . . . . 18 7. Security Considerations
8. IANA considerations . . . . . . . . . . . . . . . . . . . . . 18 8. IANA Considerations
8.1. Well-Known 'private-token-issuer-directory' URI . . . . . 18 8.1. Well-Known "private-token-issuer-directory" URI
8.2. Token Type Registry Updates . . . . . . . . . . . . . . . 19 8.2. Privacy Pass Token Types
8.2.1. Token Type VOPRF (P-384, SHA-384) . . . . . . . . . . 19 8.2.1. Token Type VOPRF(P-384, SHA-384)
8.2.2. Token Type Blind RSA (2048-bit) . . . . . . . . . . . 19 8.2.2. Token Type Blind RSA (2048-bit)
8.3. Media Types . . . . . . . . . . . . . . . . . . . . . . . 20 8.3. Media Types
8.3.1. "application/private-token-issuer-directory" media 8.3.1. "application/private-token-issuer-directory" Media Type
type . . . . . . . . . . . . . . . . . . . . . . . . 20 8.3.2. "application/private-token-request" Media Type
8.3.2. "application/private-token-request" media type . . . 21 8.3.3. "application/private-token-response" Media Type
8.3.3. "application/private-token-response" media type . . . 21 9. References
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 22 9.1. Normative References
9.1. Normative References . . . . . . . . . . . . . . . . . . 22 9.2. Informative References
9.2. Informative References . . . . . . . . . . . . . . . . . 23 Appendix A. Test Vectors
Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 24 A.1. Issuance Protocol 1 - VOPRF(P-384, SHA-384)
Appendix B. Test Vectors . . . . . . . . . . . . . . . . . . . . 24 A.2. Issuance Protocol 2 - Blind RSA, 2048
B.1. Issuance Protocol 1 - VOPRF(P-384, SHA-384) . . . . . . . 24 Acknowledgements
B.2. Issuance Protocol 2 - Blind RSA, 2048 . . . . . . . . . . 27 Authors' Addresses
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 39
1. Introduction 1. Introduction
The Privacy Pass protocol provides a privacy-preserving authorization The Privacy Pass protocol provides a privacy-preserving authorization
mechanism. In essence, the protocol allows clients to provide mechanism. In essence, the protocol allows clients to provide
cryptographic tokens that prove nothing other than that they have cryptographic tokens that prove nothing other than that they have
been created by a given server in the past [ARCHITECTURE]. been created by a given server in the past [ARCHITECTURE].
This document describes the issuance protocol for Privacy Pass built This document describes the issuance protocol for Privacy Pass built
on [HTTP]. It specifies two variants: one that is privately on [HTTP]. It specifies two variants: one that is privately
verifiable using the issuance private key based on the oblivious verifiable using the issuance private key based on the Oblivious
pseudorandom function from [OPRF], and one that is publicly Pseudorandom Function (OPRF) as defined in [OPRF] and one that is
verifiable using the issuance public key based on the blind RSA publicly verifiable using the issuance public key based on the blind
signature scheme [BLINDRSA]. RSA signature scheme [BLINDRSA].
This document does not cover the Privacy Pass architecture, including This document does not cover the Privacy Pass architecture, including
choices that are necessary for deployment and application specific choices that are necessary for deployment and application-specific
choices for protecting client privacy. This information is covered choices for protecting client privacy. This information is covered
in [ARCHITECTURE]. in [ARCHITECTURE].
2. Terminology 2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in "OPTIONAL" in this document are to be interpreted as described in
BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
This document uses the terms Origin, Client, Issuer, and Token as This document uses the terms "Origin", "Client", "Issuer", and
defined in Section 2 of [ARCHITECTURE]. Moreover, the following "Token" as defined in Section 2 of [ARCHITECTURE]. Moreover, the
additional terms are used throughout this document. following additional terms are used throughout this document.
* Issuer Public Key: The public key (from a private-public key pair) Issuer Public Key: The public key (from a private-public key pair)
used by the Issuer for issuing and verifying Tokens. used by the Issuer for issuing and verifying Tokens.
* Issuer Private Key: The private key (from a private-public key Issuer Private Key: The private key (from a private-public key pair)
pair) used by the Issuer for issuing and verifying Tokens. used by the Issuer for issuing and verifying Tokens.
Unless otherwise specified, this document encodes protocol messages Unless otherwise specified, this document encodes protocol messages
in TLS notation from Section 3 of [TLS13]. Moreover, all constants in TLS notation ([TLS13], Section 3). Moreover, all constants are in
are in network byte order. network byte order.
3. Protocol Overview 3. Protocol Overview
The issuance protocols defined in this document embody the core of The issuance protocols defined in this document embody the core of
Privacy Pass. Clients receive TokenChallenge inputs from the Privacy Pass. Clients receive TokenChallenge inputs from the
redemption protocol ([AUTHSCHEME], Section 2.1) and use the issuance redemption protocol ([AUTHSCHEME], Section 2.1) and use the issuance
protocols to produce corresponding Token values ([AUTHSCHEME], protocols to produce corresponding Token values ([AUTHSCHEME],
Section 2.2). The issuance protocol describes how Clients and Section 2.2). The issuance protocol describes how Clients and
Issuers interact to compute a token using a one-round protocol Issuers interact to compute a token using a one-round protocol
consisting of a TokenRequest from the Client and TokenResponse from consisting of a TokenRequest from the Client and a TokenResponse from
the Issuer. This interaction is shown below. the Issuer. This interaction is shown below.
+--------+ +--------+ +----------+ +--------+ +--------+ +--------+ +----------+ +--------+
| Origin | | Client | | Attester | | Issuer | | Origin | | Client | | Attester | | Issuer |
+---+----+ +---+----+ +----+-----+ +---+----+ +---+----+ +---+----+ +----+-----+ +---+----+
| | | | | | | |
|<----- Request ------+ | | |<----- Request ------+ | |
+-- TokenChallenge -->| | | +-- TokenChallenge -->| | |
| |<== Attestation ==>| | | |<== Attestation ==>| |
| | | | | | | |
| +--------- TokenRequest ------->| | +--------- TokenRequest ------->|
| |<-------- TokenResponse -------+ | |<-------- TokenResponse -------+
|<-- Request+Token ---+ | | |<-- Request+Token ---+ | |
| | | | | | | |
Figure 1: Issuance Overview Figure 1: Issuance Overview
The TokenChallenge inputs to the issuance protocols described in this The TokenChallenge inputs to the issuance protocols described in this
document can be interactive or non-interactive, and per-origin or document can be interactive or non-interactive and can be per origin
cross-origin. or across origins.
The issuance protocols defined in this document are compatible with The issuance protocols defined in this document are compatible with
any deployment model defined in Section 4 of [ARCHITECTURE]. The any deployment model defined in Section 4 of [ARCHITECTURE]. The
details of attestation are outside the scope of the issuance details of attestation are outside the scope of the issuance
protocol; see Section 4 of [ARCHITECTURE] for information about how protocol; see Section 4 of [ARCHITECTURE] for information about how
attestation can be implemented in each of the relevant deployment attestation can be implemented in each of the relevant deployment
models. models.
This document describes two variants of the issuance protocol: one This document describes two variants of the issuance protocol: one
that is privately verifiable (Section 5) using the issuance private that is privately verifiable (Section 5) using the issuance private
key based on the oblivious pseudorandom function from [OPRF], and one key based on the OPRF [OPRF] and one that is publicly verifiable
that is publicly verifiable (Section 6) using the issuance public key (Section 6) using the issuance public key based on the blind RSA
based on the blind RSA signature scheme [BLINDRSA]. signature scheme [BLINDRSA].
4. Configuration 4. Configuration
Issuers MUST provide two parameters for configuration: Issuers MUST provide two parameters for configuration:
1. Issuer Request URL: A token request URL for generating access Issuer Request URL: A token request URL for generating access
tokens. For example, an Issuer URL might be tokens. For example, an Issuer Request URL might be
https://issuer.example.net/request. <https://issuer.example.net/request>.
2. Issuer Public Key values: A list of Issuer Public Keys for the Issuer Public Key values: A list of Issuer Public Keys for the
issuance protocol. issuance protocol.
The Issuer parameters can be obtained from an Issuer via a directory The Issuer parameters can be obtained from an Issuer via a directory
object, which is a JSON object ([RFC8259], Section 4) whose values object, which is a JSON object ([RFC8259], Section 4) whose values
are other JSON values ([RFC8259], Section 3) for the parameters. The are other JSON values ([RFC8259], Section 3) for the parameters. The
contents of this JSON object are defined in Table 1. contents of this JSON object are defined in Table 1.
+====================+======================================+ +====================+======================================+
| Field Name | Value | | Field Name | Value |
+====================+======================================+ +====================+======================================+
| issuer-request-uri | Issuer Request URL value (as an | | issuer-request-uri | Issuer Request URL value (as an |
| | absolute URL, or a URL relative to | | | absolute URL or as a URL relative to |
| | the directory object) as a percent- | | | the directory object) as a percent- |
| | encoded URL string, represented as a | | | encoded URL string, represented as a |
| | JSON string ([RFC8259], Section 7) | | | JSON string ([RFC8259], Section 7) |
+--------------------+--------------------------------------+ +--------------------+--------------------------------------+
| token-keys | List of Issuer Public Key values, | | token-keys | List of Issuer Public Key values, |
| | each represented as JSON objects | | | each represented as JSON objects |
| | ([RFC8259], Section 4) | | | ([RFC8259], Section 4) |
+--------------------+--------------------------------------+ +--------------------+--------------------------------------+
Table 1: Issuer directory object description Table 1: Issuer Directory Object Description
Each "token-keys" JSON object contains the fields and corresponding Each "token-keys" JSON object contains the fields and corresponding
raw values defined in Table 2. raw values defined in Table 2.
+============+====================================================+ +============+=====================================================+
| Field Name | Value | | Field Name | Value |
+============+====================================================+ +============+=====================================================+
| token-type | Integer value of the Token Type, as defined in | | token-type | Integer value of the token type, as defined in |
| | Section 8.2, represented as a JSON number | | | Section 8.2, represented as a JSON number |
| | ([RFC8259], Section 6) | | | ([RFC8259], Section 6) |
+------------+----------------------------------------------------+ +------------+-----------------------------------------------------+
| token-key | The base64url-encoded [RFC4648] Public Key for use | | token-key | The base64url public key, encoded per [RFC4648], |
| | with the issuance protocol as determined by the | | | for use with the issuance protocol as determined by |
| | token-type field, including padding, represented | | | the token-type field, including padding, |
| | as a JSON string ([RFC8259], Section 7) | | | represented as a JSON string ([RFC8259], Section 7) |
+------------+----------------------------------------------------+ +------------+-----------------------------------------------------+
Table 2: Issuer 'token-keys' object description' Table 2: Issuer "token-keys" Object Description
Each "token-keys" JSON object may also contain the optional field Each "token-keys" JSON object may also contain the optional field
"not-before". The value of this field is the UNIX timestamp (number "not-before". The value of this field is the UNIX timestamp (number
of seconds since January 1, 1970, UTC -- see Section 4.2.1 of of seconds since January 1, 1970, UTC -- see Section 4.2.1 of
[TIMESTAMP]) at which the key can be used. If this field is present, [TIMESTAMP]) at which the key can be used. If this field is present,
Clients SHOULD NOT use a token key before this timestamp, as doing so Clients SHOULD NOT use a token key before this timestamp, as doing so
can lead to issuance failures. The purpose of this field is to can lead to issuance failures. The purpose of this field is to
assist in scheduled key rotations. assist in scheduled key rotations.
Beyond staging keys with the "not-before" value, Issuers MAY Beyond staging keys with the "not-before" value, Issuers MAY
advertise multiple "token-keys" for the same token-type to facilitate advertise multiple "token-keys" for the same token-type to facilitate
key rotation. In this case, Issuers indicate preference for which key rotation. In this case, Issuers indicate their preference for
token key to use based on the order of keys in the list, with which token key to use based on the order of keys in the list, with
preference given to keys earlier in the list. Clients SHOULD use the preference given to keys earlier in the list. Clients SHOULD use the
first key in the "token-keys" list that either does not have a "not- first key in the "token-keys" list that either does not have a "not-
before" value or has a "not-before" value in the past, since the before" value or has a "not-before" value in the past, since the
first such key is the most likely to be valid in the given time first such key is the most likely to be valid in the given time
window. Origins can attempt to use any key in the "token-keys" list window. Origins can attempt to use any key in the "token-keys" list
to verify tokens, starting with the most preferred key in the list. to verify tokens, starting with the most preferred key in the list.
Trial verification like this can help deal with Client clock skew. Trial verifications like this can help deal with Client clock skew.
Altogether, the Issuer's directory could look like the following Altogether, the Issuer's directory could look like the following
(with the "token-key" fields abbreviated): (with the "token-key" fields abbreviated):
{ {
"issuer-request-uri": "https://issuer.example.net/request", "issuer-request-uri": "https://issuer.example.net/request",
"token-keys": [ "token-keys": [
{ {
"token-type": 2, "token-type": 2,
"token-key": "MI...AB", "token-key": "MI...AB",
skipping to change at page 7, line 5 skipping to change at line 268
Clients that use this directory resource before 1686913811 in UNIX Clients that use this directory resource before 1686913811 in UNIX
time would use the second key in the "token-keys" list, whereas time would use the second key in the "token-keys" list, whereas
Clients that use this directory after 1686913811 in UNIX time would Clients that use this directory after 1686913811 in UNIX time would
use the first key in the "token-keys" list. use the first key in the "token-keys" list.
A complete "token-key" value, encoded as it would be in the Issuer A complete "token-key" value, encoded as it would be in the Issuer
directory, would look like the following (line breaks are inserted to directory, would look like the following (line breaks are inserted to
fit within the per-line character limits): fit within the per-line character limits):
$ echo MIIBUjA9BgkqhkiG9w0BAQowMKANMAsGCWCGSAFlAwQCAqEaMBgGCSqGSIb3DQEBCDAL \ $ echo MIIBUjA9BgkqhkiG9w0BAQowMKANMAsGCWCGSAFlAwQCAqEaMBgGCSqGSIb3DQE \
BglghkgBZQMEAgKiAwIBMAOCAQ8AMIIBCgKCAQEAmKHGAMyeoJt1pj3n7xTtqAPr_DhZAPhJM7 \ BCDALBglghkgBZQMEAgKiAwIBMAOCAQ8AMIIBCgKCAQEAmKHGAMyeoJt1pj3n7xTtqAPr \
Pc8ENR2BzdZwPTTF7KFKms5wt-mL01at0SC-cdBuIj6WYK8Ovz0AyaBuvTvW6SKCh7ZPXEqCGR \ _DhZAPhJM7Pc8ENR2BzdZwPTTF7KFKms5wt-mL01at0SC-cdBuIj6WYK8Ovz0AyaBuvTv \
sq5I0nthREtrYkGo113oMVPVp3sy4VHPgzd8KdzTLGzOrjiUOsSFWbjf21iaVjXJ2VdwdS-8O- \ W6SKCh7ZPXEqCGRsq5I0nthREtrYkGo113oMVPVp3sy4VHPgzd8KdzTLGzOrjiUOsSFWb \
430wkucYjGeOJwi8rWx_ZkcHtav0S67Q_SlExJel6nyRzpuuID9OQm1nxfs1Z4PhWBzt93T2oz \ jf21iaVjXJ2VdwdS-8O-430wkucYjGeOJwi8rWx_ZkcHtav0S67Q_SlExJel6nyRzpuuI \
Tnda3OklF5n0pIXD6bttmTekIw_8Xx2LMis0jfJ1QL99aA-muXRFN4ZUwORrF7cAcCUD_-56_6 \ D9OQm1nxfs1Z4PhWBzt93T2ozTnda3OklF5n0pIXD6bttmTekIw_8Xx2LMis0jfJ1QL99 \
fh9s34FmqBGwIDAQAB \ aA-muXRFN4ZUwORrF7cAcCUD_-56_6fh9s34FmqBGwIDAQAB \
| sed s/-/+/g | sed s/_/\\//g | openssl base64 -d \ | sed s/-/+/g | sed s/_/\\//g | openssl base64 -d \
| openssl asn1parse -dump -inform DER | openssl asn1parse -dump -inform DER
0:d=0 hl=4 l= 338 cons: SEQUENCE 0:d=0 hl=4 l= 338 cons: SEQUENCE
4:d=1 hl=2 l= 61 cons: SEQUENCE 4:d=1 hl=2 l= 61 cons: SEQUENCE
6:d=2 hl=2 l= 9 prim: OBJECT :rsassaPss 6:d=2 hl=2 l= 9 prim: OBJECT :rsassaPss
17:d=2 hl=2 l= 48 cons: SEQUENCE 17:d=2 hl=2 l= 48 cons: SEQUENCE
19:d=3 hl=2 l= 13 cons: cont [ 0 ] 19:d=3 hl=2 l= 13 cons: cont [ 0 ]
21:d=4 hl=2 l= 11 cons: SEQUENCE 21:d=4 hl=2 l= 11 cons: SEQUENCE
23:d=5 hl=2 l= 9 prim: OBJECT :sha384 23:d=5 hl=2 l= 9 prim: OBJECT :sha384
34:d=3 hl=2 l= 26 cons: cont [ 1 ] 34:d=3 hl=2 l= 26 cons: cont [ 1 ]
skipping to change at page 7, line 34 skipping to change at line 297
49:d=5 hl=2 l= 11 cons: SEQUENCE 49:d=5 hl=2 l= 11 cons: SEQUENCE
51:d=6 hl=2 l= 9 prim: OBJECT :sha384 51:d=6 hl=2 l= 9 prim: OBJECT :sha384
62:d=3 hl=2 l= 3 cons: cont [ 2 ] 62:d=3 hl=2 l= 3 cons: cont [ 2 ]
64:d=4 hl=2 l= 1 prim: INTEGER :30 64:d=4 hl=2 l= 1 prim: INTEGER :30
67:d=1 hl=4 l= 271 prim: BIT STRING 67:d=1 hl=4 l= 271 prim: BIT STRING
... truncated public key bytes ... ... truncated public key bytes ...
Issuer directory resources have the media type "application/private- Issuer directory resources have the media type "application/private-
token-issuer-directory" and are located at the well-known location token-issuer-directory" and are located at the well-known location
/.well-known/private-token-issuer-directory; see Section 8.1 for the /.well-known/private-token-issuer-directory; see Section 8.1 for the
registration information for this well-known URI. The reason that registration information for this well-known URI. This resource is
this resource is located at a well-known URI is that Issuers are located at a well-known URI because Issuers are defined by an origin
defined by an origin name in TokenChallenge structures; see name in TokenChallenge structures; see Section 2.1 of [AUTHSCHEME].
Section 2.1 of [AUTHSCHEME].
The Issuer directory and Issuer resources SHOULD be available on the The Issuer directory and Issuer resources SHOULD be available on the
same origin. If an Issuer wants to service multiple different Issuer same origin. If an Issuer wants to service multiple different Issuer
directories they MUST create unique subdomains for each so the directories, they MUST create unique subdomains for each directory so
TokenChallenge defined in Section 2.1 of [AUTHSCHEME] can be the TokenChallenge defined in Section 2.1 of [AUTHSCHEME] can be
differentiated correctly. differentiated correctly.
Issuers SHOULD use HTTP cache directives to permit caching of this Issuers SHOULD use HTTP cache directives to permit caching of this
resource [RFC5861]. The cache lifetime depends on the Issuer's key resource [RFC5861]. The cache lifetime depends on the Issuer's key
rotation schedule. Regular rotation of token keys is recommended to rotation schedule. Regular rotation of token keys is recommended to
minimize the risk of key compromise and any harmful effects that minimize the risk of key compromise and any harmful effects that
happen due to key compromise. happen due to key compromise.
Issuers can control cache lifetime with the Cache-Control header, as Issuers can control the cache lifetime with the Cache-Control header,
follows: as follows:
Cache-Control: max-age=86400 Cache-Control: max-age=86400
Consumers of the Issuer directory resource SHOULD follow the usual Consumers of the Issuer directory resource SHOULD follow the usual
HTTP caching [RFC9111] semantics when processing this resource. Long HTTP caching semantics [RFC9111] when processing this resource. Long
cache lifetimes may result in use of stale Issuer configuration cache lifetimes may result in the use of stale Issuer configuration
information, whereas short lifetimes may result in decreased information, whereas short lifetimes may result in decreased
performance. When use of an Issuer configuration results in token performance. When the use of an Issuer configuration results in
issuance failures, e.g., because the Issuer has invalidated its token issuance failures, e.g., because the Issuer has invalidated its
directory resource before its expiration time and issuance requests directory resource before its expiration time and issuance requests
using this configuration are unsuccessful, the directory SHOULD be using this configuration are unsuccessful, the directory SHOULD be
fetched and revalidated. Issuance will continue to fail until the fetched and revalidated. Issuance will continue to fail until the
Issuer configuration is updated. Issuer configuration is updated.
5. Issuance Protocol for Privately Verifiable Tokens 5. Issuance Protocol for Privately Verifiable Tokens
The privately verifiable issuance protocol allows Clients to produce The privately verifiable issuance protocol allows Clients to produce
Token values that verify using the Issuer Private Key. This protocol Token values that verify using the Issuer Private Key. This protocol
is based on the oblivious pseudorandom function from [OPRF]. is based on the OPRF [OPRF].
Issuers provide a Issuer Private and Public Key, denoted skI and pkI Issuers provide an Issuer Private Key and Public Key, denoted skI and
respectively, used to produce tokens as input to the protocol. See pkI, respectively, used to produce tokens as input to the protocol.
Section 5.5 for how these keys are generated. See Section 5.5 for information about how these keys are generated.
Clients provide the following as input to the issuance protocol: Clients provide the following as input to the issuance protocol:
* Issuer Request URL: A URL identifying the location to which Issuer Request URL: A URL identifying the location to which issuance
issuance requests are sent. This can be a URL derived from the requests are sent. This can be a URL derived from the "issuer-
"issuer-request-uri" value in the Issuer's directory resource, or request-uri" value in the Issuer's directory resource, or it can
it can be another Client-configured URL. The value of this be another Client-configured URL. The value of this parameter
parameter depends on the Client configuration and deployment depends on the Client configuration and deployment model. For
model. For example, in the 'Joint Origin and Issuer' deployment example, in the "Joint Origin and Issuer" deployment model
model, the Issuer Request URL might correspond to the Client's ([ARCHITECTURE], Section 4.3), the Issuer Request URL might
configured Attester, and the Attester is configured to relay correspond to the Client's configured Attester, and the Attester
requests to the Issuer. is configured to relay requests to the Issuer.
* Issuer name: An identifier for the Issuer. This is typically a Issuer name: An identifier for the Issuer. This is typically a
host name that can be used to construct HTTP requests to the hostname that can be used to construct HTTP requests to the
Issuer. Issuer.
* Issuer Public Key: pkI, with a key identifier token_key_id Issuer Public Key: pkI, with a key identifier token_key_id computed
computed as described in Section 5.5. as described in Section 5.5.
* Challenge value: challenge, an opaque byte string. For example, Challenge value: challenge -- an opaque byte string. For example,
this might be provided by the redemption protocol in [AUTHSCHEME]. this might be provided by the redemption protocol described in
[AUTHSCHEME].
Given this configuration and these inputs, the two messages exchanged Given this configuration and these inputs, the two messages exchanged
in this protocol are described below. This section uses notation in this protocol are described below. This section uses notation
described in [OPRF], Section 4, including SerializeElement and described in [OPRF], Section 4, including SerializeElement and
DeserializeElement, SerializeScalar and DeserializeScalar, and DeserializeElement, SerializeScalar and DeserializeScalar, and
DeriveKeyPair. DeriveKeyPair.
The constants Ne and Ns are as defined in [OPRF], Section 4 for The constants Ne and Ns are as defined in [OPRF], Section 4 for
OPRF(P-384, SHA-384). The constant Nk, which is also equal to Nh as OPRF(P-384, SHA-384). For this protocol, the constant Nk, which is
defined in [OPRF], Section 4, is defined by Section 8.2.1. also equal to Nh as defined in [OPRF], Section 4, is defined by
Section 8.2.1.
5.1. Client-to-Issuer Request 5.1. Client-to-Issuer Request
The Client first creates a context as follows: The Client first creates a context as follows:
client_context = SetupVOPRFClient("P384-SHA384", pkI) client_context = SetupVOPRFClient("P384-SHA384", pkI)
Here, "P384-SHA384" is the identifier corresponding to the Here, "P384-SHA384" is the identifier corresponding to the
OPRF(P-384, SHA-384) ciphersuite in [OPRF]. SetupVOPRFClient is OPRF(P-384, SHA-384) ciphersuite defined in [OPRF]. SetupVOPRFClient
defined in [OPRF], Section 3.2. is defined in [OPRF], Section 3.2.
The Client then creates an issuance request message for a random The Client then creates an issuance request message for a random
32-byte value nonce with the input challenge and Issuer key 32-byte value nonce with the input challenge and Issuer key
identifier as described below: identifier as described below:
nonce = random(32) nonce = random(32)
challenge_digest = SHA256(challenge) challenge_digest = SHA256(challenge)
token_input = concat(0x0001, // Token type field is 2 bytes long token_input = concat(0x0001, // Token type field is 2 bytes long
nonce, nonce,
challenge_digest, challenge_digest,
skipping to change at page 10, line 19 skipping to change at line 425
token_key_id (Section 5.5) in network byte order (in other words, token_key_id (Section 5.5) in network byte order (in other words,
the last 8 bits of token_key_id). This value is truncated so that the last 8 bits of token_key_id). This value is truncated so that
Issuers cannot use token_key_id as a way of uniquely identifying Issuers cannot use token_key_id as a way of uniquely identifying
Clients; see Section 7 and referenced information for more Clients; see Section 7 and referenced information for more
details. details.
* "blinded_msg" is the Ne-octet blinded message defined above, * "blinded_msg" is the Ne-octet blinded message defined above,
computed as SerializeElement(blinded_element). computed as SerializeElement(blinded_element).
The values token_input and blinded_element are stored locally and The values token_input and blinded_element are stored locally and
used later as described in Section 5.3. The Client then generates an used later, as described in Section 5.3. The Client then generates
HTTP POST request to send to the Issuer Request URL, with the an HTTP POST request to send to the Issuer Request URL, with the
TokenRequest as the content. The media type for this request is TokenRequest as the content. The media type for this request is
"application/private-token-request". An example request for the "application/private-token-request". An example request for the
Issuer Request URL "https://issuer.example.net/request" is shown Issuer Request URL "https://issuer.example.net/request" is shown
below. below.
POST /request HTTP/1.1 POST /request HTTP/1.1
Host: issuer.example.net Host: issuer.example.net
Accept: application/private-token-response Accept: application/private-token-response
Content-Type: application/private-token-request Content-Type: application/private-token-request
Content-Length: <Length of TokenRequest> Content-Length: <Length of TokenRequest>
skipping to change at page 10, line 42 skipping to change at line 448
<Bytes containing the TokenRequest> <Bytes containing the TokenRequest>
5.2. Issuer-to-Client Response 5.2. Issuer-to-Client Response
Upon receipt of the request, the Issuer validates the following Upon receipt of the request, the Issuer validates the following
conditions: conditions:
* The TokenRequest contains a supported token_type. * The TokenRequest contains a supported token_type.
* The TokenRequest.truncated_token_key_id corresponds to the * The TokenRequest.truncated_token_key_id corresponds to the
truncated key ID of a Public Key owned by the Issuer. truncated key ID of a public key owned by the Issuer.
* The TokenRequest.blinded_msg is of the correct size. * The TokenRequest.blinded_msg is of the correct size.
If any of these conditions is not met, the Issuer MUST return an HTTP If any of these conditions are not met, the Issuer MUST return an
422 (Unprocessable Content) error to the client. HTTP 422 (Unprocessable Content) error to the client.
If these conditions are met, the Issuer then tries to deserialize If these conditions are met, the Issuer then tries to deserialize
TokenRequest.blinded_msg using DeserializeElement from Section 2.1 of TokenRequest.blinded_msg using DeserializeElement ([OPRF],
[OPRF], yielding blinded_element. If this fails, the Issuer MUST Section 2.1), yielding blinded_element. If this fails, the Issuer
return an HTTP 422 (Unprocessable Content) error to the client. MUST return an HTTP 422 (Unprocessable Content) error to the client.
Otherwise, if the Issuer is willing to produce a token to the Client, Otherwise, if the Issuer is willing to produce a token to the Client,
the Issuer completes the issuance flow by computing a blinded the Issuer completes the issuance flow by computing a blinded
response as follows: response as follows:
server_context = SetupVOPRFServer("P384-SHA384", skI) server_context = SetupVOPRFServer("P384-SHA384", skI)
evaluate_element, proof = evaluate_element, proof =
server_context.BlindEvaluate(skI, pkI, blinded_element) server_context.BlindEvaluate(skI, pkI, blinded_element)
SetupVOPRFServer is defined in [OPRF], Section 3.2 and BlindEvaluate SetupVOPRFServer is defined in [OPRF], Section 3.2, and BlindEvaluate
is defined in [OPRF], Section 3.3.2. The Issuer then creates a is defined in [OPRF], Section 3.3.2. The Issuer then creates a
TokenResponse structured as follows: TokenResponse structured as follows:
struct { struct {
uint8_t evaluate_msg[Ne]; uint8_t evaluate_msg[Ne];
uint8_t evaluate_proof[Ns+Ns]; uint8_t evaluate_proof[Ns+Ns];
} TokenResponse; } TokenResponse;
The structure fields are defined as follows: The structure fields are defined as follows:
skipping to change at page 12, line 16 skipping to change at line 519
succeeds, the Client then constructs a Token as follows: succeeds, the Client then constructs a Token as follows:
struct { struct {
uint16_t token_type = 0x0001; /* Type VOPRF(P-384, SHA-384) */ uint16_t token_type = 0x0001; /* Type VOPRF(P-384, SHA-384) */
uint8_t nonce[32]; uint8_t nonce[32];
uint8_t challenge_digest[32]; uint8_t challenge_digest[32];
uint8_t token_key_id[32]; uint8_t token_key_id[32];
uint8_t authenticator[Nk]; uint8_t authenticator[Nk];
} Token; } Token;
The Token.nonce value is that which was created in Section 5.1. If The Token.nonce value is the value that was created according to
the Finalize function fails, the Client aborts the protocol. Section 5.1. If the Finalize function fails, the Client aborts the
protocol.
5.4. Token Verification 5.4. Token Verification
Verifying a Token requires creating a VOPRF context using the Issuer Verifying a Token requires creating a Verifiable Oblivious
Private Key and Public Key, evaluating the token contents, and Pseudorandom Function (VOPRF) context using the Issuer Private Key
comparing the result against the token authenticator value: and Public Key, evaluating the token contents, and comparing the
result against the token authenticator value:
server_context = SetupVOPRFServer("P384-SHA384", skI) server_context = SetupVOPRFServer("P384-SHA384", skI)
token_authenticator_input = token_authenticator_input =
concat(Token.token_type, concat(Token.token_type,
Token.nonce, Token.nonce,
Token.challenge_digest, Token.challenge_digest,
Token.token_key_id) Token.token_key_id)
token_authenticator = token_authenticator =
server_context.Evaluate(token_authenticator_input) server_context.Evaluate(token_authenticator_input)
valid = (token_authenticator == Token.authenticator) valid = (token_authenticator == Token.authenticator)
5.5. Issuer Configuration 5.5. Issuer Configuration
Issuers are configured with Issuer Private and Public Keys, each Issuers are configured with Issuer Private Keys and Public Keys, each
denoted skI and pkI, respectively, used to produce tokens. These denoted skI and pkI, respectively, used to produce tokens. These
keys MUST NOT be reused in other protocols. A RECOMMENDED method for keys MUST NOT be reused in other protocols. A RECOMMENDED method for
generating keys is as follows: generating keys is as follows:
seed = random(Ns) seed = random(Ns)
(skI, pkI) = DeriveKeyPair(seed, "PrivacyPass") (skI, pkI) = DeriveKeyPair(seed, "PrivacyPass")
The DeriveKeyPair function is defined in [OPRF], Section 3.3.1. The The DeriveKeyPair function is defined in [OPRF], Section 3.2.1. The
key identifier for a public key pkI, denoted token_key_id, is key identifier for a public key pkI, denoted token_key_id, is
computed as follows: computed as follows:
token_key_id = SHA256(SerializeElement(pkI)) token_key_id = SHA256(SerializeElement(pkI))
Since Clients truncate token_key_id in each TokenRequest, Issuers Since Clients truncate token_key_id in each TokenRequest, Issuers
SHOULD ensure that the truncated form of new key IDs do not collide SHOULD ensure that the truncated forms of new key IDs do not collide
with other truncated key IDs in rotation. Collisions can cause the with other truncated key IDs in rotation. Collisions can cause the
Issuer to use the wrong Issuer Private Key for issuance, which will Issuer to use the wrong Issuer Private Key for issuance, which will
in turn cause the resulting tokens to be invalid. There is no known in turn cause the resulting tokens to be invalid. There is no known
security consequence of using the the wrong Issuer Private Key. A security consequence of using the wrong Issuer Private Key. A
possible exception to this constraint would be a colliding key that possible exception to this constraint would be a colliding key that
is still in use but in the process of being rotated out, in which is still in use but is in the process of being rotated out, in which
case the collision cannot reasonably be avoided but it is expected to case the collision cannot reasonably be avoided; however, this
be transient. situation is expected to be transient.
6. Issuance Protocol for Publicly Verifiable Tokens 6. Issuance Protocol for Publicly Verifiable Tokens
This section describes a variant of the issuance protocol in This section describes a variant of the issuance protocol discussed
Section 5 for producing publicly verifiable tokens using the protocol in Section 5 for producing publicly verifiable tokens using the
in [BLINDRSA]. In particular, this variant of the issuance protocol protocol defined in [BLINDRSA]. In particular, this variant of the
works for the RSABSSA-SHA384-PSS-Deterministic and RSABSSA-SHA384- issuance protocol works for the RSABSSA-SHA384-PSS-Deterministic and
PSSZERO-Deterministic blind RSA protocol variants described in RSABSSA-SHA384-PSSZERO-Deterministic blind RSA protocol variants
Section 5 of [BLINDRSA]. described in Section 5 of [BLINDRSA].
The publicly verifiable issuance protocol differs from the protocol The publicly verifiable issuance protocol differs from the protocol
in Section 5 in that the output tokens are publicly verifiable by defined in Section 5 in that the output tokens are publicly
anyone with the Issuer Public Key. This means any Origin can select a verifiable by anyone with the Issuer Public Key. This means any
given Issuer to produce tokens, as long as the Origin has the Issuer Origin can select a given Issuer to produce tokens, as long as the
public key, without explicit coordination or permission from the Origin has the Issuer Public Key, without explicit coordination or
Issuer. This is because the Issuer does not learn the Origin that permission from the Issuer. This is because the Issuer does not
requested the token during the issuance protocol. learn the Origin that requested the token during the issuance
protocol.
Beyond this difference, the publicly verifiable issuance protocol Beyond this difference, the publicly verifiable issuance protocol
variant is nearly identical to the privately verifiable issuance variant is nearly identical to the privately verifiable issuance
protocol variant. In particular, Issuers provide an Issuer Private protocol variant. In particular, Issuers provide an Issuer Private
and Public Key, denoted skI and pkI, respectively, used to produce Key and Public Key, denoted skI and pkI, respectively, used to
tokens as input to the protocol. See Section 6.5 for how these keys produce tokens as input to the protocol. See Section 6.5 for
are generated. information about how these keys are generated.
Clients provide the following as input to the issuance protocol: Clients provide the following as input to the issuance protocol:
* Issuer Request URL: A URL identifying the location to which Issuer Request URL: A URL identifying the location to which issuance
issuance requests are sent. This can be a URL derived from the requests are sent. This can be a URL derived from the "issuer-
"issuer-request-uri" value in the Issuer's directory resource, or request-uri" value in the Issuer's directory resource, or it can
it can be another Client-configured URL. The value of this be another Client-configured URL. The value of this parameter
parameter depends on the Client configuration and deployment depends on the Client configuration and deployment model. For
model. For example, in the 'Split Origin, Attester, Issuer' example, in the "Split Origin, Attester, Issuer" deployment model
deployment model, the Issuer Request URL might correspond to the ([ARCHITECTURE], Section 4.4), the Issuer Request URL might
Client's configured Attester, and the Attester is configured to correspond to the Client's configured Attester, and the Attester
relay requests to the Issuer. is configured to relay requests to the Issuer.
* Issuer name: An identifier for the Issuer. This is typically a Issuer name: An identifier for the Issuer. This is typically a
host name that can be used to construct HTTP requests to the hostname that can be used to construct HTTP requests to the
Issuer. Issuer.
* Issuer Public Key: pkI, with a key identifier token_key_id Issuer Public Key: pkI, with a key identifier token_key_id computed
computed as described in Section 6.5. as described in Section 6.5.
* Challenge value: challenge, an opaque byte string. For example, Challenge value: challenge -- an opaque byte string. For example,
this might be provided by the redemption protocol in [AUTHSCHEME]. this might be provided by the redemption protocol described in
[AUTHSCHEME].
Given this configuration and these inputs, the two messages exchanged Given this configuration and these inputs, the two messages exchanged
in this protocol are described below. The constant Nk is defined by in this protocol are described below. For this protocol, the
Section 8.2.2. constant Nk is defined by Section 8.2.2.
6.1. Client-to-Issuer Request 6.1. Client-to-Issuer Request
The Client first creates an issuance request message for a random The Client first creates an issuance request message for a random
32-byte value nonce using the input challenge and Issuer key 32-byte value nonce using the input challenge and Issuer key
identifier as follows: identifier as follows:
nonce = random(32) nonce = random(32)
challenge_digest = SHA256(challenge) challenge_digest = SHA256(challenge)
token_input = concat(0x0002, // Token type field is 2 bytes long token_input = concat(0x0002, // Token type field is 2 bytes long
nonce, nonce,
challenge_digest, challenge_digest,
token_key_id) token_key_id)
blinded_msg, blind_inv = blinded_msg, blind_inv =
Blind(pkI, PrepareIdentity(token_input)) Blind(pkI, PrepareIdentity(token_input))
The PrepareIdentity and Blind functions are defined in Section 4.1 of The PrepareIdentity and Blind functions are defined in Sections 4.1
[BLINDRSA] and Section 4.2 of [BLINDRSA], respectively. The Client and 4.2 of [BLINDRSA], respectively. The Client stores the nonce and
stores the nonce and challenge_digest values locally for use when challenge_digest values locally for use when finalizing the issuance
finalizing the issuance protocol to produce a token (as described in protocol to produce a token (as described in Section 6.3).
Section 6.3).
The Client then creates a TokenRequest structured as follows: The Client then creates a TokenRequest structured as follows:
struct { struct {
uint16_t token_type = 0x0002; /* Type Blind RSA (2048-bit) */ uint16_t token_type = 0x0002; /* Type Blind RSA (2048-bit) */
uint8_t truncated_token_key_id; uint8_t truncated_token_key_id;
uint8_t blinded_msg[Nk]; uint8_t blinded_msg[Nk];
} TokenRequest; } TokenRequest;
The structure fields are defined as follows: The structure fields are defined as follows:
skipping to change at page 15, line 40 skipping to change at line 687
Upon receipt of the request, the Issuer validates the following Upon receipt of the request, the Issuer validates the following
conditions: conditions:
* The TokenRequest contains a supported token_type. * The TokenRequest contains a supported token_type.
* The TokenRequest.truncated_token_key_id corresponds to the * The TokenRequest.truncated_token_key_id corresponds to the
truncated key ID of an Issuer Public Key. truncated key ID of an Issuer Public Key.
* The TokenRequest.blinded_msg is of the correct size. * The TokenRequest.blinded_msg is of the correct size.
If any of these conditions is not met, the Issuer MUST return an HTTP If any of these conditions are not met, the Issuer MUST return an
422 (Unprocessable Content) error to the Client. Otherwise, if the HTTP 422 (Unprocessable Content) error to the Client. Otherwise, if
Issuer is willing to produce a token to the Client, the Issuer the Issuer is willing to produce a token to the Client, the Issuer
completes the issuance flow by computing a blinded response as completes the issuance flow by computing a blinded response as
follows: follows:
blind_sig = BlindSign(skI, TokenRequest.blinded_msg) blind_sig = BlindSign(skI, TokenRequest.blinded_msg)
The BlindSign function is defined in Section 4.3 of [BLINDRSA]. The The BlindSign function is defined in Section 4.3 of [BLINDRSA]. The
result is encoded and transmitted to the client in the following result is encoded and transmitted to the client in the following
TokenResponse structure: TokenResponse structure:
struct { struct {
skipping to change at page 16, line 39 skipping to change at line 733
[AUTHSCHEME] as follows: [AUTHSCHEME] as follows:
struct { struct {
uint16_t token_type = 0x0002; /* Type Blind RSA (2048-bit) */ uint16_t token_type = 0x0002; /* Type Blind RSA (2048-bit) */
uint8_t nonce[32]; uint8_t nonce[32];
uint8_t challenge_digest[32]; uint8_t challenge_digest[32];
uint8_t token_key_id[32]; uint8_t token_key_id[32];
uint8_t authenticator[Nk]; uint8_t authenticator[Nk];
} Token; } Token;
The Token.nonce value is that which was sampled in Section 5.1. If The Token.nonce value is the value that was sampled according to
the Finalize function fails, the Client aborts the protocol. Section 5.1. If the Finalize function fails, the Client aborts the
protocol.
6.4. Token Verification 6.4. Token Verification
Verifying a Token requires checking that Token.authenticator is a Verifying a Token requires checking that Token.authenticator is a
valid signature over the remainder of the token input using the valid signature over the remainder of the token input using the
Issuer Public Key. The function RSASSA-PSS-VERIFY is defined in Issuer Public Key. The function RSASSA-PSS-VERIFY is defined in
Section 8.1.2 of [RFC8017], using SHA-384 as the Hash function, MGF1 Section 8.1.2 of [RFC8017], using SHA-384 as the hash function, MGF1
with SHA-384 as the PSS mask generation function (MGF), and a 48-byte with SHA-384 as the Probabilistic Signature Scheme (PSS) mask
salt length (sLen). generation function (MGF), and a 48-byte salt length (sLen).
token_authenticator_input = token_authenticator_input =
concat(Token.token_type, concat(Token.token_type,
Token.nonce, Token.nonce,
Token.challenge_digest, Token.challenge_digest,
Token.token_key_id) Token.token_key_id)
valid = RSASSA-PSS-VERIFY(pkI, valid = RSASSA-PSS-VERIFY(pkI,
token_authenticator_input, token_authenticator_input,
Token.authenticator) Token.authenticator)
6.5. Issuer Configuration 6.5. Issuer Configuration
Issuers are configured with Issuer Private and Public Keys, each Issuers are configured with Issuer Private Keys and Public Keys, each
denoted skI and pkI, respectively, used to produce tokens. Each key denoted skI and pkI, respectively, used to produce tokens. Each key
SHALL be generated securely, for example as specified in FIPS 186-5 SHALL be generated securely -- for example, as specified in FIPS
[DSS]. These keys MUST NOT be reused in other protocols. 186-5 [DSS]. These keys MUST NOT be reused in other protocols.
The key identifier for an Issuer Private and Public Key (skI, pkI), The key identifier for an Issuer Private Key and Public Key (skI,
denoted token_key_id, is computed as SHA256(encoded_key), where pkI), denoted token_key_id, is computed as SHA256(encoded_key), where
encoded_key is a DER-encoded SubjectPublicKeyInfo [RFC5280] (SPKI) encoded_key is a DER-encoded SubjectPublicKeyInfo (SPKI) object
object carrying pkI as a DER-encoded RSAPublicKey value [RFC5756] in [RFC5280] carrying pkI as a DER-encoded RSAPublicKey value [RFC5756]
the subjectPublicKey field. Additionally, the SPKI object MUST use in the subjectPublicKey field. Additionally, the SPKI object MUST
the id-RSASSA-PSS object identifier in the algorithm field within the use the id-RSASSA-PSS object identifier in the algorithm field within
SPKI object, the parameters field MUST contain a RSASSA-PSS-params the SPKI object, the parameters field MUST contain an RSASSA-PSS-
value, and MUST include the hashAlgorithm, maskGenAlgorithm, and params value, and MUST include the hashAlgorithm, maskGenAlgorithm,
saltLength values. The saltLength MUST match the output size of the and saltLength values. The saltLength MUST match the output size of
hash function associated with the public key and token type. the hash function associated with the public key and token type.
An example sequence of the SPKI object (in ASN.1 format, with the An example sequence of the SPKI object (in ASN.1 format, with the
actual public key bytes truncated) for a 2048-bit key is below: actual public key bytes truncated) for a 2048-bit key is shown below:
$ cat spki.bin | xxd -r -p | openssl asn1parse -dump -inform DER $ cat spki.bin | xxd -r -p | openssl asn1parse -dump -inform DER
0:d=0 hl=4 l= 338 cons: SEQUENCE 0:d=0 hl=4 l= 338 cons: SEQUENCE
4:d=1 hl=2 l= 61 cons: SEQUENCE 4:d=1 hl=2 l= 61 cons: SEQUENCE
6:d=2 hl=2 l= 9 prim: OBJECT :rsassaPss 6:d=2 hl=2 l= 9 prim: OBJECT :rsassaPss
17:d=2 hl=2 l= 48 cons: SEQUENCE 17:d=2 hl=2 l= 48 cons: SEQUENCE
19:d=3 hl=2 l= 13 cons: cont [ 0 ] 19:d=3 hl=2 l= 13 cons: cont [ 0 ]
21:d=4 hl=2 l= 11 cons: SEQUENCE 21:d=4 hl=2 l= 11 cons: SEQUENCE
23:d=5 hl=2 l= 9 prim: OBJECT :sha384 23:d=5 hl=2 l= 9 prim: OBJECT :sha384
34:d=3 hl=2 l= 26 cons: cont [ 1 ] 34:d=3 hl=2 l= 26 cons: cont [ 1 ]
36:d=4 hl=2 l= 24 cons: SEQUENCE 36:d=4 hl=2 l= 24 cons: SEQUENCE
38:d=5 hl=2 l= 9 prim: OBJECT :mgf1 38:d=5 hl=2 l= 9 prim: OBJECT :mgf1
49:d=5 hl=2 l= 11 cons: SEQUENCE 49:d=5 hl=2 l= 11 cons: SEQUENCE
51:d=6 hl=2 l= 9 prim: OBJECT :sha384 51:d=6 hl=2 l= 9 prim: OBJECT :sha384
62:d=3 hl=2 l= 3 cons: cont [ 2 ] 62:d=3 hl=2 l= 3 cons: cont [ 2 ]
64:d=4 hl=2 l= 1 prim: INTEGER :30 64:d=4 hl=2 l= 1 prim: INTEGER :30
67:d=1 hl=4 l= 271 prim: BIT STRING 67:d=1 hl=4 l= 271 prim: BIT STRING
... truncated public key bytes ... ... truncated public key bytes ...
Since Clients truncate token_key_id in each TokenRequest, Issuers Since Clients truncate token_key_id in each TokenRequest, Issuers
SHOULD ensure that the truncated form of new key IDs do not collide SHOULD ensure that the truncated forms of new key IDs do not collide
with other truncated key IDs in rotation. Collisions can cause the with other truncated key IDs in rotation. Collisions can cause the
Issuer to use the wrong Issuer Private Key for issuance, which will Issuer to use the wrong Issuer Private Key for issuance, which will
in turn cause the resulting tokens to be invalid. There is no known in turn cause the resulting tokens to be invalid. There is no known
security consequence of using the the wrong Issuer Private Key. A security consequence of using the wrong Issuer Private Key. A
possible exception to this constraint would be a colliding key that possible exception to this constraint would be a colliding key that
is still in use but in the process of being rotated out, in which is still in use but is in the process of being rotated out, in which
case the collision cannot reasonably be avoided but it is expected to case the collision cannot reasonably be avoided; however, this
be transient. situation is expected to be transient.
7. Security considerations 7. Security Considerations
This document outlines how to instantiate the Issuance protocol based This document outlines how to instantiate the issuance protocol based
on the VOPRF defined in [OPRF] and blind RSA protocol defined in on the VOPRF defined in [OPRF] and the blind RSA protocol defined in
[BLINDRSA]. All security considerations described in the VOPRF and [BLINDRSA]. All security considerations described in the VOPRF and
blind RSA documents also apply in the Privacy Pass use-case. blind RSA documents also apply in the Privacy Pass use case.
Considerations related to broader privacy and security concerns in a Considerations related to broader privacy and security concerns in a
multi-Client and multi-Issuer setting are deferred to the multi-Client and multi-Issuer setting are covered in the architecture
architecture document [ARCHITECTURE]. In particular, Section 4 and document [ARCHITECTURE]. In particular, Sections 4 and 5 of
Section 5 of [ARCHITECTURE] discuss relevant privacy considerations [ARCHITECTURE] discuss relevant privacy considerations influenced by
influenced by the Privacy Pass deployment model, and Section 6 of the Privacy Pass deployment models, and Section 6 of [ARCHITECTURE]
[ARCHITECTURE] discusses privacy considerations that apply regardless discusses privacy considerations that apply regardless of deployment
of deployment model. Notable considerations include those pertaining model. Notable considerations include those pertaining to Issuer
to Issuer Public Key rotation and consistency, where consistency is Public Key rotation and consistency -- where consistency is as
as described in [CONSISTENCY], and Issuer selection. described in [CONSISTENCY] -- and Issuer selection.
8. IANA considerations
This section contains considerations for IANA. 8. IANA Considerations
8.1. Well-Known 'private-token-issuer-directory' URI 8.1. Well-Known "private-token-issuer-directory" URI
This document updates the "Well-Known URIs" Registry [WellKnownURIs] IANA has updated the "Well-Known URIs" registry [WellKnownURIs] with
with the following values. the following values.
+===============+============+===========+===========+=============+ +===============+============+===========+===========+=============+
| URI Suffix | Change | Reference | Status | Related | | URI Suffix | Change | Reference | Status | Related |
| | Controller | | | information | | | Controller | | | Information |
+===============+============+===========+===========+=============+ +===============+============+===========+===========+=============+
| private- | IETF | [this | permanent | None | | private- | IETF | RFC 9578 | permanent | None |
| token-issuer- | | document] | | | | token-issuer- | | | | |
| directory | | | | | | directory | | | | |
+---------------+------------+-----------+-----------+-------------+ +---------------+------------+-----------+-----------+-------------+
Table 3: 'private-token-issuer-directory' Well-Known URI Table 3: "private-token-issuer-directory" Well-Known URI
8.2. Token Type Registry Updates
This document updates the "Privacy Pass Token Type" Registry with the
following entries.
8.2.1. Token Type VOPRF (P-384, SHA-384) 8.2. Privacy Pass Token Types
* Value: 0x0001 IANA has updated the "Privacy Pass Token Type" registry with the
entries below.
* Name: VOPRF (P-384, SHA-384) 8.2.1. Token Type VOPRF(P-384, SHA-384)
* Token Structure: As defined in Section 2.2 of [AUTHSCHEME] Value: 0x0001
Name: VOPRF(P-384, SHA-384)
Token Structure: As defined in Section 2.2 of [AUTHSCHEME].
Token Key Encoding: Serialized using SerializeElement (Section 2.1
of [OPRF]).
TokenChallenge Structure: As defined in Section 2.1 of [AUTHSCHEME].
Public Verifiability: N
Public Metadata: N
Private Metadata: N
Nk: 48
Nid: 32
Reference: RFC 9578, Section 5
Notes: None
* Token Key Encoding: Serialized using SerializeElement from 8.2.2. Token Type Blind RSA (2048-bit)
Section 2.1 of [OPRF]
* TokenChallenge Structure: As defined in Section 2.1 of Value: 0x0002
[AUTHSCHEME] Name: Blind RSA (2048-bit)
Token Structure: As defined in Section 2.2 of [AUTHSCHEME].
Token Key Encoding: Serialized as a DER-encoded SubjectPublicKeyInfo
(SPKI) object using the RSASSA-PSS OID [RFC5756].
TokenChallenge Structure: As defined in Section 2.1 of [AUTHSCHEME].
Public Verifiability: Y
Public Metadata: N
Private Metadata: N
Nk: 256
Nid: 32
Reference: RFC 9578, Section 6
Notes: The RSABSSA-SHA384-PSS-Deterministic and RSABSSA-SHA384-
PSSZERO-Deterministic variants are supported.
* Public Verifiability: N 8.3. Media Types
* Public Metadata: N IANA has added the following entries to the "Media Types" registry:
* Private Metadata: N * "application/private-token-issuer-directory"
* Nk: 48 * "application/private-token-request"
* Nid: 32 * "application/private-token-response"
* Reference: Section 5 The templates for these entries are listed below. The reference is
this RFC.
* Notes: None 8.3.1. "application/private-token-issuer-directory" Media Type
8.2.2. Token Type Blind RSA (2048-bit) Type name: application
* Value: 0x0002 Subtype name: private-token-issuer-directory
* Name: Blind RSA (2048-bit) Required parameters: N/A
* Token Structure: As defined in Section 2.2 of [AUTHSCHEME] Optional parameters: N/A
* Token Key Encoding: Serialized as a DER-encoded Encoding considerations: binary
SubjectPublicKeyInfo (SPKI) object using the RSASSA-PSS OID
[RFC5756]
* TokenChallenge Structure: As defined in Section 2.1 of Security considerations: See Section 7 of RFC 9578.
[AUTHSCHEME]
* Public Verifiability: Y Interoperability considerations: N/A
* Public Metadata: N Published specification: RFC 9578
* Private Metadata: N Applications that use this media type: Services that implement the
Privacy Pass issuer role, and client applications that interact
with the issuer for the purposes of issuing or redeeming tokens.
* Nk: 256 Fragment identifier considerations: N/A
* Nid: 32 Additional information:
* Reference: Section 6 Deprecated alias names for this type: N/A
Magic number(s): N/A
File extension(s): N/A
Macintosh file type code(s): N/A
* Notes: The RSABSSA-SHA384-PSS-Deterministic and RSABSSA-SHA384- Person & email address to contact for further information: See the
PSSZERO-Deterministic variants are supported Authors' Addresses section of RFC 9578.
8.3. Media Types Intended usage: COMMON
The following entries should be added to the IANA "media types" Restrictions on usage: N/A
registry:
* "application/private-token-issuer-directory" Author: See the Authors' Addresses section of RFC 9578.
* "application/private-token-request" Change controller: IETF
* "application/private-token-response" 8.3.2. "application/private-token-request" Media Type
The templates for these entries are listed below and the reference Type name: application
should be this RFC.
8.3.1. "application/private-token-issuer-directory" media type Subtype name: private-token-request
Type name: application
Subtype name: private-token-issuer-directory
Required parameters: N/A Required parameters: N/A
Optional parameters: N/A Optional parameters: N/A
Encoding considerations: "binary"
Security considerations: see Section 4
Interoperability considerations: N/A
Published specification: this specification
Applications that use this media type: Services that implement the
Privacy Pass issuer role, and client applications that interact
with the issuer for the purposes of issuing or redeeming tokens.
Fragment identifier considerations: N/A
Additional information: Magic number(s): N/A
Deprecated alias names for this type: N/A
File extension(s): N/A
Macintosh file type code(s): N/A
Person and email address to contact for further information: see Aut
hors' Addresses section
Intended usage: COMMON
Restrictions on usage: N/A
Author: see Authors' Addresses section
Change controller: IETF
8.3.2. "application/private-token-request" media type Encoding considerations: binary
Security considerations: See Section 7 of RFC 9578.
Type name: application
Subtype name: private-token-request
Required parameters: N/A
Optional parameters: N/A
Encoding considerations: "binary"
Security considerations: see Section 7
Interoperability considerations: N/A Interoperability considerations: N/A
Published specification: this specification
Published specification: RFC 9578
Applications that use this media type: Applications that want to Applications that use this media type: Applications that want to
issue or facilitate issuance of Privacy Pass tokens, including issue or facilitate issuance of Privacy Pass tokens, including
Privacy Pass issuer applications themselves. Privacy Pass issuer applications themselves.
Fragment identifier considerations: N/A Fragment identifier considerations: N/A
Additional information: Magic number(s): N/A
Deprecated alias names for this type: N/A Additional information:
File extension(s): N/A
Macintosh file type code(s): N/A Deprecated alias names for this type: N/A
Person and email address to contact for further information: see Aut Magic number(s): N/A
hors' Addresses section File extension(s): N/A
Macintosh file type code(s): N/A
Person & email address to contact for further information: See the
Authors' Addresses section of RFC 9578.
Intended usage: COMMON Intended usage: COMMON
Restrictions on usage: N/A Restrictions on usage: N/A
Author: see Authors' Addresses section
Author: See the Authors' Addresses section of RFC 9578.
Change controller: IETF Change controller: IETF
8.3.3. "application/private-token-response" media type 8.3.3. "application/private-token-response" Media Type
Type name: application Type name: application
Subtype name: private-token-response Subtype name: private-token-response
Required parameters: N/A Required parameters: N/A
Optional parameters: N/A Optional parameters: N/A
Encoding considerations: "binary"
Security considerations: see Section 7 Encoding considerations: binary
Security considerations: See Section 7 of RFC 9578.
Interoperability considerations: N/A Interoperability considerations: N/A
Published specification: this specification
Published specification: RFC 9578
Applications that use this media type: Applications that want to Applications that use this media type: Applications that want to
issue or facilitate issuance of Privacy Pass tokens, including issue or facilitate issuance of Privacy Pass tokens, including
Privacy Pass issuer applications themselves. Privacy Pass issuer applications themselves.
Fragment identifier considerations: N/A Fragment identifier considerations: N/A
Additional information: Magic number(s): N/A
Deprecated alias names for this type: N/A Additional information:
File extension(s): N/A
Macintosh file type code(s): N/A Deprecated alias names for this type: N/A
Person and email address to contact for further information: see Aut Magic number(s): N/A
hors' Addresses section File extension(s): N/A
Macintosh file type code(s): N/A
Person & email address to contact for further information: See the
Authors' Addresses section of RFC 9578.
Intended usage: COMMON Intended usage: COMMON
Restrictions on usage: N/A Restrictions on usage: N/A
Author: see Authors' Addresses section
Author: See the Authors' Addresses section of RFC 9578.
Change controller: IETF Change controller: IETF
9. References 9. References
9.1. Normative References 9.1. Normative References
[ARCHITECTURE] [ARCHITECTURE]
Davidson, A., Iyengar, J., and C. A. Wood, "The Privacy Davidson, A., Iyengar, J., and C. A. Wood, "The Privacy
Pass Architecture", Work in Progress, Internet-Draft, Pass Architecture", RFC 9576, DOI 10.17487/RFC9576, May
draft-ietf-privacypass-architecture-16, 25 September 2023, 2024, <https://www.rfc-editor.org/info/rfc9576>.
<https://datatracker.ietf.org/doc/html/draft-ietf-
privacypass-architecture-16>.
[AUTHSCHEME] [AUTHSCHEME]
Pauly, T., Valdez, S., and C. A. Wood, "The Privacy Pass Pauly, T., Valdez, S., and C. A. Wood, "The Privacy Pass
HTTP Authentication Scheme", Work in Progress, Internet- HTTP Authentication Scheme", RFC 9577,
Draft, draft-ietf-privacypass-auth-scheme-14, 25 September DOI 10.17487/RFC9577, May 2024,
2023, <https://datatracker.ietf.org/doc/html/draft-ietf- <https://www.rfc-editor.org/info/rfc9577>.
privacypass-auth-scheme-14>.
[BLINDRSA] Denis, F., Jacobs, F., and C. A. Wood, "RSA Blind [BLINDRSA] Denis, F., Jacobs, F., and C. A. Wood, "RSA Blind
Signatures", Work in Progress, Internet-Draft, draft-irtf- Signatures", RFC 9474, DOI 10.17487/RFC9474, October 2023,
cfrg-rsa-blind-signatures-14, 10 July 2023, <https://www.rfc-editor.org/info/rfc9474>.
<https://datatracker.ietf.org/doc/html/draft-irtf-cfrg-
rsa-blind-signatures-14>.
[HTTP] Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke, [HTTP] Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke,
Ed., "HTTP Semantics", STD 97, RFC 9110, Ed., "HTTP Semantics", STD 97, RFC 9110,
DOI 10.17487/RFC9110, June 2022, DOI 10.17487/RFC9110, June 2022,
<https://www.rfc-editor.org/rfc/rfc9110>. <https://www.rfc-editor.org/info/rfc9110>.
[OPRF] Davidson, A., Faz-Hernandez, A., Sullivan, N., and C. A. [OPRF] Davidson, A., Faz-Hernandez, A., Sullivan, N., and C. A.
Wood, "Oblivious Pseudorandom Functions (OPRFs) using Wood, "Oblivious Pseudorandom Functions (OPRFs) Using
Prime-Order Groups", Work in Progress, Internet-Draft, Prime-Order Groups", RFC 9497, DOI 10.17487/RFC9497,
draft-irtf-cfrg-voprf-21, 21 February 2023, December 2023, <https://www.rfc-editor.org/info/rfc9497>.
<https://datatracker.ietf.org/doc/html/draft-irtf-cfrg-
voprf-21>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/rfc/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[RFC4648] Josefsson, S., "The Base16, Base32, and Base64 Data [RFC4648] Josefsson, S., "The Base16, Base32, and Base64 Data
Encodings", RFC 4648, DOI 10.17487/RFC4648, October 2006, Encodings", RFC 4648, DOI 10.17487/RFC4648, October 2006,
<https://www.rfc-editor.org/rfc/rfc4648>. <https://www.rfc-editor.org/info/rfc4648>.
[RFC5756] Turner, S., Brown, D., Yiu, K., Housley, R., and T. Polk, [RFC5756] Turner, S., Brown, D., Yiu, K., Housley, R., and T. Polk,
"Updates for RSAES-OAEP and RSASSA-PSS Algorithm "Updates for RSAES-OAEP and RSASSA-PSS Algorithm
Parameters", RFC 5756, DOI 10.17487/RFC5756, January 2010, Parameters", RFC 5756, DOI 10.17487/RFC5756, January 2010,
<https://www.rfc-editor.org/rfc/rfc5756>. <https://www.rfc-editor.org/info/rfc5756>.
[RFC5861] Nottingham, M., "HTTP Cache-Control Extensions for Stale [RFC5861] Nottingham, M., "HTTP Cache-Control Extensions for Stale
Content", RFC 5861, DOI 10.17487/RFC5861, May 2010, Content", RFC 5861, DOI 10.17487/RFC5861, May 2010,
<https://www.rfc-editor.org/rfc/rfc5861>. <https://www.rfc-editor.org/info/rfc5861>.
[RFC8017] Moriarty, K., Ed., Kaliski, B., Jonsson, J., and A. Rusch, [RFC8017] Moriarty, K., Ed., Kaliski, B., Jonsson, J., and A. Rusch,
"PKCS #1: RSA Cryptography Specifications Version 2.2", "PKCS #1: RSA Cryptography Specifications Version 2.2",
RFC 8017, DOI 10.17487/RFC8017, November 2016, RFC 8017, DOI 10.17487/RFC8017, November 2016,
<https://www.rfc-editor.org/rfc/rfc8017>. <https://www.rfc-editor.org/info/rfc8017>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/rfc/rfc8174>. May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8259] Bray, T., Ed., "The JavaScript Object Notation (JSON) Data [RFC8259] Bray, T., Ed., "The JavaScript Object Notation (JSON) Data
Interchange Format", STD 90, RFC 8259, Interchange Format", STD 90, RFC 8259,
DOI 10.17487/RFC8259, December 2017, DOI 10.17487/RFC8259, December 2017,
<https://www.rfc-editor.org/rfc/rfc8259>. <https://www.rfc-editor.org/info/rfc8259>.
[RFC9111] Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke, [RFC9111] Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke,
Ed., "HTTP Caching", STD 98, RFC 9111, Ed., "HTTP Caching", STD 98, RFC 9111,
DOI 10.17487/RFC9111, June 2022, DOI 10.17487/RFC9111, June 2022,
<https://www.rfc-editor.org/rfc/rfc9111>. <https://www.rfc-editor.org/info/rfc9111>.
[TIMESTAMP] [TIMESTAMP]
Mizrahi, T., Fabini, J., and A. Morton, "Guidelines for Mizrahi, T., Fabini, J., and A. Morton, "Guidelines for
Defining Packet Timestamps", RFC 8877, Defining Packet Timestamps", RFC 8877,
DOI 10.17487/RFC8877, September 2020, DOI 10.17487/RFC8877, September 2020,
<https://www.rfc-editor.org/rfc/rfc8877>. <https://www.rfc-editor.org/info/rfc8877>.
[TLS13] Rescorla, E., "The Transport Layer Security (TLS) Protocol [TLS13] Rescorla, E., "The Transport Layer Security (TLS) Protocol
Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018, Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
<https://www.rfc-editor.org/rfc/rfc8446>. <https://www.rfc-editor.org/info/rfc8446>.
[WellKnownURIs] [WellKnownURIs]
"Well-Known URIs", n.d., IANA, "Well-Known URIs",
<https://www.iana.org/assignments/well-known-uris/well- <https://www.iana.org/assignments/well-known-uris/>.
known-uris.xhtml>.
9.2. Informative References 9.2. Informative References
[CONSISTENCY] [CONSISTENCY]
Davidson, A., Finkel, M., Thomson, M., and C. A. Wood, Davidson, A., Finkel, M., Thomson, M., and C. A. Wood,
"Key Consistency and Discovery", Work in Progress, "Key Consistency and Discovery", Work in Progress,
Internet-Draft, draft-ietf-privacypass-key-consistency-01, Internet-Draft, draft-ietf-privacypass-key-consistency-01,
10 July 2023, <https://datatracker.ietf.org/doc/html/ 10 July 2023, <https://datatracker.ietf.org/doc/html/
draft-ietf-privacypass-key-consistency-01>. draft-ietf-privacypass-key-consistency-01>.
[DSS] Moody, D. and National Institute of Standards and [DSS] National Institute of Standards and Technology, "Digital
Technology, "Digital Signature Standard (DSS)", Signature Standard (DSS)", NIST FIPS Publication 186-5,
DOI 10.6028/nist.fips.186-5, 2023, DOI 10.6028/NIST.FIPS.186-5, February 2023,
<https://doi.org/10.6028/nist.fips.186-5>. <https://doi.org/10.6028/nist.fips.186-5>.
[RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S., [RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
Housley, R., and W. Polk, "Internet X.509 Public Key Housley, R., and W. Polk, "Internet X.509 Public Key
Infrastructure Certificate and Certificate Revocation List Infrastructure Certificate and Certificate Revocation List
(CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008, (CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008,
<https://www.rfc-editor.org/rfc/rfc5280>. <https://www.rfc-editor.org/info/rfc5280>.
Appendix A. Acknowledgements
The authors of this document would like to acknowledge the helpful
feedback and discussions from Benjamin Schwartz, Joseph Salowey, and
Tara Whalen.
Appendix B. Test Vectors Appendix A. Test Vectors
This section includes test vectors for the two basic issuance This section includes test vectors for the two basic issuance
protocols specified in this document. Appendix B.1 contains test protocols specified in this document. Appendix A.1 contains test
vectors for token issuance protocol 1 (0x0001), and Appendix B.2 vectors for token issuance protocol 1 (0x0001), and Appendix A.2
contains test vectors for token issuance protocol 2 (0x0002). contains test vectors for token issuance protocol 2 (0x0002).
B.1. Issuance Protocol 1 - VOPRF(P-384, SHA-384) A.1. Issuance Protocol 1 - VOPRF(P-384, SHA-384)
The test vector below lists the following values: The test vectors below list the following values:
* skS: The Issuer Private Key, serialized using SerializeScalar from skS: The Issuer Private Key, serialized using SerializeScalar
Section 2.1 of [OPRF] and represented as a hexadecimal string. ([OPRF], Section 2.1) and represented as a hexadecimal string.
* pkS: The Issuer Public Key, serialized according to the encoding pkS: The Issuer Public Key, serialized according to the encoding in
in Section 8.2.1. Section 8.2.1.
* token_challenge: A randomly generated TokenChallenge structure, token_challenge: A randomly generated TokenChallenge structure,
represented as a hexadecimal string. represented as a hexadecimal string.
* nonce: The 32-byte client nonce generated according to nonce: The 32-byte client nonce generated according to Section 5.1,
Section 5.1, represented as a hexadecimal string. represented as a hexadecimal string.
* blind: The blind used when computing the OPRF blinded message, blind: The blind used when computing the OPRF blinded message,
serialized using SerializeScalar from Section 2.1 of [OPRF] and serialized using SerializeScalar ([OPRF], Section 2.1) and
represented as a hexadecimal string. represented as a hexadecimal string.
* token_request: The TokenRequest message constructed according to token_request: The TokenRequest message constructed according to
Section 5.1, represented as a hexadecimal string. Section 5.1, represented as a hexadecimal string.
* token_response: The TokenResponse message constructed according to token_response: The TokenResponse message constructed according to
Section 5.2, represented as a hexadecimal string. Section 5.2, represented as a hexadecimal string.
* token: The output Token from the protocol, represented as a token: The output Token from the protocol, represented as a
hexadecimal string. hexadecimal string.
// Test vector 1 // Test vector 1
skS: 39b0d04d3732459288fc5edb89bb02c2aa42e06709f201d6c518871d5181 skS: 39b0d04d3732459288fc5edb89bb02c2aa42e06709f201d6c518871d5181
14910bee3c919bed1bbffe3fc1b87d53240a 14910bee3c919bed1bbffe3fc1b87d53240a
pkS: 02d45bf522425cdd2227d3f27d245d9d563008829252172d34e48469290c pkS: 02d45bf522425cdd2227d3f27d245d9d563008829252172d34e48469290c
21da1a46d42ca38f7beabdf05c074aee1455bf 21da1a46d42ca38f7beabdf05c074aee1455bf
token_challenge: 0001000e6973737565722e6578616d706c65205de58a52fc token_challenge: 0001000e6973737565722e6578616d706c65205de58a52fc
daef25ca3f65448d04e040fb1924e8264acfccfc6c5ad451d582b3000e6f72696 daef25ca3f65448d04e040fb1924e8264acfccfc6c5ad451d582b3000e6f72696
7696e2e6578616d706c65 7696e2e6578616d706c65
skipping to change at page 27, line 41 skipping to change at line 1272
71f056276f32f89c09947eca8ff119d940d9d57c2fcbd83d2da494ddeb37dc1f6 71f056276f32f89c09947eca8ff119d940d9d57c2fcbd83d2da494ddeb37dc1f6
78e5661a8e7bcc96b3477eb89d708b0ce10e0ea1b5ce0001f9332f743c0cc3d47 78e5661a8e7bcc96b3477eb89d708b0ce10e0ea1b5ce0001f9332f743c0cc3d47
48233fea6d3152fae7844821268eb96ba491f60b1a3a848849310a39e9ef59121 48233fea6d3152fae7844821268eb96ba491f60b1a3a848849310a39e9ef59121
669aa5d5dbb4b4deb532d2f907a01c5b39efaf23985080 669aa5d5dbb4b4deb532d2f907a01c5b39efaf23985080
token: 00019ee54942d8a1604452a76856b1bfaf1cd608e1e3fa38acfd9f13e8 token: 00019ee54942d8a1604452a76856b1bfaf1cd608e1e3fa38acfd9f13e8
4483c90e89d4380df12a1727f4e2ca1ee0d7abea0d0fb1e9506507a4dd618f9b8 4483c90e89d4380df12a1727f4e2ca1ee0d7abea0d0fb1e9506507a4dd618f9b8
7e79f9f3521a7c9134d6722925bf622a994041cdb1b082cdf1309af32f0ce00ca 7e79f9f3521a7c9134d6722925bf622a994041cdb1b082cdf1309af32f0ce00ca
1dab63e1b603747a8a5c3b46c7c2853de5ec7af8cac7cf3e089cecdc9ed3ff05c 1dab63e1b603747a8a5c3b46c7c2853de5ec7af8cac7cf3e089cecdc9ed3ff05c
d24504fe4f6c52d24ac901471267d8b63b61e6b d24504fe4f6c52d24ac901471267d8b63b61e6b
B.2. Issuance Protocol 2 - Blind RSA, 2048 A.2. Issuance Protocol 2 - Blind RSA, 2048
The test vector below lists the following values: The test vectors below list the following values:
* skS: The PEM-encoded PKCS#8 RSA Issuer Private Key used for skS: The PEM-encoded PKCS #8 RSA Issuer Private Key used for signing
signing tokens, represented as a hexadecimal string. tokens, represented as a hexadecimal string.
* pkS: The Issuer Public Key, serialized according to the encoding pkS: The Issuer Public Key, serialized according to the encoding in
in Section 8.2.2. Section 8.2.2.
* token_challenge: A randomly generated TokenChallenge structure, token_challenge: A randomly generated TokenChallenge structure,
represented as a hexadecimal string. represented as a hexadecimal string.
* nonce: The 32-byte client nonce generated according to nonce: The 32-byte client nonce generated according to Section 6.1,
Section 6.1, represented as a hexadecimal string. represented as a hexadecimal string.
* blind: The blind used when computing the blind RSA blinded blind: The blind used when computing the blind RSA blinded message,
message, represented as a hexadecimal string. represented as a hexadecimal string.
* salt: The randomly generated 48-byte salt used when encoding the salt: The randomly generated 48-byte salt used when encoding the
blinded token request message, represented as a hexadecimal blinded token request message, represented as a hexadecimal
string. string.
* token_request: The TokenRequest message constructed according to token_request: The TokenRequest message constructed according to
Section 6.1, represented as a hexadecimal string. Section 6.1, represented as a hexadecimal string.
* token_request: The TokenResponse message constructed according to token_response: The TokenResponse message constructed according to
Section 6.2, represented as a hexadecimal string. Section 6.2, represented as a hexadecimal string.
* token: The output Token from the protocol, represented as a token: The output Token from the protocol, represented as a
hexadecimal string. hexadecimal string.
// Test vector 1 // Test vector 1
skS: 2d2d2d2d2d424547494e2050524956415445204b45592d2d2d2d2d0a4d49 skS: 2d2d2d2d2d424547494e2050524956415445204b45592d2d2d2d2d0a4d49
4945765149424144414e42676b71686b6947397730424151454641415343424b6 4945765149424144414e42676b71686b6947397730424151454641415343424b6
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Acknowledgements
The authors of this document would like to acknowledge the helpful
feedback and discussions from Benjamin Schwartz, Joseph Salowey, and
Tara Whalen.
Authors' Addresses Authors' Addresses
Sofía Celi Sofía Celi
Brave Software Brave Software
Lisbon Lisbon
Portugal Portugal
Email: cherenkov@riseup.net Email: cherenkov@riseup.net
Alex Davidson Alex Davidson
Brave Software Brave Software
Lisbon Lisbon
Portugal Portugal
Email: alex.davidson92@gmail.com Email: alex.davidson92@gmail.com
Steven Valdez Steven Valdez
Google LLC Google LLC
Email: svaldez@chromium.org Email: svaldez@chromium.org
Christopher A. Wood Christopher A. Wood
Cloudflare Cloudflare
101 Townsend St 101 Townsend St
San Francisco, San Francisco, CA 94107
United States of America United States of America
Email: caw@heapingbits.net Email: caw@heapingbits.net
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