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icrc_32_sign_challenge.md

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ICRC-32: Sign Challenge

ON HOLD EXTENDS 25

Authors: Philipp Litzenberger, Frederik Rothenberger

Summary

The purpose of the icrc32_sign_challenge method is for the relying party to receive a cryptographic proof of ownership for the users identities.

Method

Name: icrc32_sign_challenge

Prerequisite: Active session with granted permission scope icrc32_sign_challenge or *.

  • This scope may be restricted to specific principals.

Scope (according to the ICRC-25 standard)

Scope: icrc32_sign_challenge

Optional Properties:

  • principals (text array): A list of principals (textual representation) the scope is restricted to. If the list is not present, the scope applies to all senders (i.e. the permission is not restricted).

Example Permission Requests

No restriction:

{
    "id": 1,
    "jsonrpc": "2.0",
    "method": "icrc25_request_permissions",
    "params": {
        "scopes": [
            {
                "method": "icrc32_sign_challenge"
            }
        ]
    }
}

With restriction:

{
    "id": 1,
    "jsonrpc": "2.0",
    "method": "icrc25_request_permissions",
    "params": {
        "scopes": [
            {
                "method": "icrc32_sign_challenge",
                "principals": [
                    "btbdd-ob3pe-dz6kv-7n4gh-k2xtm-xjthz-kcvpk-fwbnv-w5qbk-iqjm4-4qe",
                    "b7gqo-ulk5n-2kpo7-oalt7-p2kyl-o4j5l-kiuwo-eeybr-dab4l-ur6up-pqe"
                ]
            }
        ]
    }
}

icrc25_supported_standards

An ICRC-25 compliant signer must implement the icrc25_supported_standards method which returns the list of supported standards. Any signer implementing ICRC-32 must include a record with the name field equal to "ICRC-32" in that list.

Request Params

principal (text): Principal (textual representation) corresponding to the identity that the signer should provide the challenge signature for.

challenge (blob): A challenge used for the signer to sign in order to prove its access to the identity. The challenge should be an array of 32 cryptographically random bytes generated from a secure random source by the sender of the request.

Result

publicKey (blob): The DER-encoded public key associated with the identity, derived in accordance with one of the signature algorithms supported by the IC. The public key can be used to derive a self-authenticating principal.

signature (blob): The signature produced by signing the concatenation of the domain separator \x13ic-signer-challenge (UTF-8 encoded) and the challenge with the private key associated with the identity.

signer_delegation (optional): An array of delegations (as defined by the IC interface specification, authentication section) delegating from the signer identity to the identity used to sign the challenge:

  • object with the following properties:
    • delegation (record): Map with fields
      • pubkey (blob): Public key as described in the IC interface specification, signatures section.
      • expiration (text): Expiration of the delegation, in nanoseconds since 1970-01-01, as a base-10 string.
      • targets (text array): A list of target canister ids (textual representation) the delegation is restricted to making canister calls to. If the list is not present, the delegation applies to all canisters (i.e. it is not restricted).
    • signature (blob): Signature on the 32-byte representation-independent hash of the map contained in the delegation field as described in IC interface specification, signatures section, using the 27 bytes \x1Aic-request-auth-delegation as the domain separator.

Message Processing

  1. The relying party sends a icrc32_sign_challenge request to the signer.
  2. Upon receiving the message, the signer first checks if it can process the message.
    • If the relying party has not been granted the permission to invoke the method for the specified principal, the signer sends a response with an error back to the relying party.
  3. The signer may ask the user to approve the request.
    • If the user does not approve the request, the signer sends a response with an error back to the relying party.
  4. The signer signs the challenge with the private keys associated with the identity corresponding to the given principal and sends a successful response with the signature (and optionally the associated signer_delegation) back to the relying party.
  5. After receiving a successful response, the relying party verifies that the signer is able to create signatures on behalf of the identity associated with the principal provided in the request:
    • The relying party validates that the self-authenticating principal derived from the publicKey in the result is equal to the principal provided in the request. If this check fails, the relying party rejects the response.
    • Determine the public key for verifying the signature of the challenge:
      • If signer_delegation is present and non-empty:
        • If the signer_delegation array contains more than 20 elements, the relying party rejects the response.
        • The relying party validates that all delegations are not expired according to their respective expiration timestamp.
        • The relying party validates all signature values of all delegations in the signer_delegation list. For the first delegation in the array, this signature must be valid with respect to the public key corresponding to the publicKey field of the identity, all subsequent delegations are signed with the key corresponding to the public key contained in the preceding delegation. The key to validate the challenge signature is the public key contained in the last delegation in the array.
      • Otherwise, the key to validate the challenge signature with is the public key contained in the publicKey field of the identity.
    • The relying party retrieves the public key to verify the challenge according to the previous step, determines the signature scheme and verifies whether it was generated by signing the concatenation of the domain separator \x13ic-signer-challenge (UTF-8 encoded) and the challenge from the request with the private key associated with that public key.
      • If the signature verification succeeds, the relying party accepts the response.
      • If the signature verification fails, the relying party rejects the response.
sequenceDiagram
    participant RP as Relying Party
    participant S as Signer
    participant U as User

    RP ->> S: Request challenge signature
    alt Scope `icrc32_sign_challenge` not granted for the principal
        S ->> RP: Error response: Permission not granted (3000)
    else
        S ->> U: Ask to approve sign challenge request
        U ->> S: Approve sign challenge request
        S ->> S: Sign the challenge
        S ->> RP: Challenge signature response
        RP ->> RP: Verify the challenge signature
    end
Loading

Errors

This standard does not define additional errors. See ICRC-25 for a list of errors that can be returned by all methods.

Examples

Without Delegation

Request

{
    "id": 1,
    "jsonrpc": "2.0",
    "method": "icrc32_sign_challenge",
    "params": {
        "principal": "2mdal-aedsb-hlpnv-qu3zl-ae6on-72bt5-fwha5-xzs74-5dkaz-dfywi-aqe",
        "challenge": "UjwgsORvEzp98TmB1cAIseNOoD9+GLyN/1DzJ5+jxZM="
    }
}

Response

{
    "id": 1,
    "jsonrpc": "2.0",
    "result": {
        "publicKey": "MFYwEAYHKoZIzj0CAQYFK4EEAAoDQgAEOTdHYwpFTr/oPXOfLQcteymk8AQE41VwPQ1W7Xpm0Zt1AY4+5aOnMAbAIjXEchxPuGbPWqPqwntXMPs3w4rOaA==",
        "signature": "bldf7qn7DC5NzTyX5kp4GpZHaEncE5/6n/Y8av3xjEwIVFAwmhyW0uM+WBXRTj4QbScot04dfaBXUOcSWF0IjQ=="
    }
}

With Delegation

Request

{
    "id": 1,
    "jsonrpc": "2.0",
    "method": "icrc32_sign_challenge",
    "params": {
        "principal": "77gyu-q2pqz-jgkwl-qtuq2-eylzf-fws5i-376hh-ra3eo-sgj65-6vod4-wae",
        "challenge": "sP4kjfTOHor/i6yENH3jMvznV56NW4oOmsCa9oV0CKQ="
    }
}

Response

{
    "id": 1,
    "jsonrpc": "2.0",
    "result": {
        "publicKey": "MDwwDAYKKwYBBAGDuEMBAgMsAAoAAAAAAGAAJwEB9YN/ErQ8yN+14qewhrU0Hm2rZZ77SrydLsSMRYHoNxM=",
        "signature": "0NE21SrrwbLO2SBDyHcqgOpJkEFB9Kbb2ERaBMUZ7vJXzK4WDVmKiMHEeeq1IBfPTfuO/4mF+zaFmo/3n+HXFA==",
        "signer_delegation": [
            {
                "delegation": {
                    "pubkey": "MFkwEwYHKoZIzj0CAQYIKoZIzj0DAQcDQgAEvHD28SXwRW2i6bgiqmel2fDV7/CDNyxkMwGh8BvmTVI+5DBSBMHJeyFZwbJEyj8Pc7rJv6XWOW+x4lsdEI4bdg==",
                    "expiration": "1702683438614940079"
                },
                "signature": "2dn3omtjZXJ0aWZpY2F0ZVkFR9nZ96NkdHJlZYMBgwGDAYMCSGNhbmlzdGVygwGDAYMBgwGDAYMBggRYIGQMSEWHMb6GjHUCQwZjEvTgayv95IMJo8/QYX7jyPNEgwGCBFggQEL7KETbIG4XJKJI7vOT9csdIigPKY2Uj8GOCkCFM0ODAYIEWCCNPbxbGsgH608xO5FxLblP30pQBoIHcZ8cujd3GyrI74MCSgAAAAAAYAAnAQGDAYMBgwJOY2VydGlmaWVkX2RhdGGCA1ggeD0/xQd42q9xciZZTb1pN52IAPye6S/kg6jpZdBqclmCBFggbM1rsxpUdh1KVunP2MujhNW4+0cYToyhPLcOBPIgms6CBFggdupn1qzaMUyZJTmGjlsaOHadwTHt/KpfEZvU6AtIsI6CBFggPeeB3ggR9ahGkWbFlPlDPZZvaG9PQGWtk5XjC/rBU+KCBFggyyqUBXAErjNvtSujkRfPkKqt7+At3+kgW8wTyPYVCgKCBFggvB+bTFT2brj8JTgekGQa5Z74fFkBhjVRYqUstIdSQsuCBFgglWeLQibPLUmNuV15R2nZ+bcBbozatDN+vL6bdHwVd6OCBFggKyt0ehAYDvkduhMP9NRBFv798A9hgRGLWw7JNAjeyKCCBFggq+kUfTfBtw6jjssoWdzVORhgjG1bIi1wnh6pRk5wAHqCBFggKsAg4MVsLKYodaOzWZAy1J8IZqiz80CZANuc7o8i9yODAYIEWCDKCPjWRprZOkS0YuyR8f3ecbbF8cZV8gQcEPRV/GmBM4MCRHRpbWWCA0n7k4S9+uvC0Bdpc2lnbmF0dXJlWDCr6WuvcRG12U2TCmsyKlM3PDIQ8aE1Sbkqt4bvPd6pqchMgvX92WC4pRTzIN2q3KhqZGVsZWdhdGlvbqJpc3VibmV0X2lkWB0sVbNH7PJobIN4HWxZ0bQ+e0y6jetsGzdhB/LNAmtjZXJ0aWZpY2F0ZVkCbtnZ96JkdHJlZYMBggRYIMb7MhQtNYSR3xisLIXqFKL4vaVCAQSFQ6fs7z0EBu16gwGDAkZzdWJuZXSDAYMBgwGDAYIEWCA1vCByZqofmhtO6jk+/pGuM+1M53Bp7Y6IHYZxat97a4MBggRYIPjD6uA3fuAIWSI78cYgL1iFxNzcj9E7HUjDyDhoiRm8gwGDAlgdLFWzR+zyaGyDeB1sWdG0PntMuo3rbBs3YQfyzQKDAYMCT2NhbmlzdGVyX3Jhbmdlc4IDWDLZ2feCgkoAAAAAAGAAAAEBSgAAAAAAYACuAQGCSgAAAAAAYACwAQFKAAAAAABv//8BAYMCSnB1YmxpY19rZXmCA1iFMIGCMB0GDSsGAQQBgtx8BQMBAgEGDCsGAQQBgtx8BQMCAQNhAJAHUSB3jrIaUwoCvMdj5/ShkpM1BpZq97VMEKTSsk3mqGsgDjRAuuYme/TEiNmhHQRyw4wbYiEZj5jk5ogro4paTjqlr86Jm3+CXtla36EmKWiAc1VvJ0dSchPo1z5AzoIEWCA2880lfZD7OOQll/GTpeAx29WFtiknk7sE20eUgDzgboIEWCACj8Xl9whoJU5yFef8Yw29Ke78NhmvF84jGQnh+vl+lYIEWCDviZXEEO1AVzHJuRP2eHnjtqa01lnSdG25prR9fnDT1YIEWCCu6rJq/kx+dkZh4N/YVkSg36UF1eIRhcFGUDBJohx4h4MCRHRpbWWCA0nErvLr7tfzzxdpc2lnbmF0dXJlWDCLPfmASgvrSN33lW6cbrU6MlvB5DoHKdP5IZV3qEbhYqKiG0FzXCtGTqk23LgIbVFkdHJlZYMBggRYIAHqRxd5i88M2z5nEO5XYddgYM7PfRwG3SO3bdKRgxB7gwJDc2lngwJYIF/Mj8qI50bwx7MJmZjxPnozy74e7q6UbbjSODnd119OgwJYIADMDx/qPEkHlzQnBKxKKfLpCN38F1j8tzhh6DZXH2H7ggNA"
            }
        ]
    }
}