Secp256k1 type

[ssadler]

Wanted to get some feedback on this; would secp256k1 signature scheme be accepted into the spec? If so, with what type ID and interface? Have attached an example below. It doesn't use Bitcoin's pubkey hashing protocol; doesn't seem worth it.

If it's open for consideration, would be good to agree on a type ID. That way, if it does get integrated, I'll already be using the right one. :slightly_smiling_face:

See also: https://github.com/libscott/komodo/blob/73b9e32b9d7ede630af0df9bae8853cd9fa1b88a/src/script/interpreter.cpp#L939

--<ASN1.PDU Crypto-Conditions.Condition, Crypto-Conditions.Fulfillment>--

Crypto-Conditions DEFINITIONS AUTOMATIC TAGS ::= BEGIN

    -- Conditions

    Condition ::= CHOICE {
      preimageSha256   [0] SimpleSha256Condition,
      prefixSha256     [1] CompoundSha256Condition,
      thresholdSha256  [2] CompoundSha256Condition,
      rsaSha256        [3] SimpleSha256Condition,
      ed25519Sha256    [4] SimpleSha256Condition,
      secp256k1Sha256  [5] SimpleSha256Condition
    }

    SimpleSha256Condition ::= SEQUENCE {
      fingerprint          OCTET STRING (SIZE(32)),
      cost                 INTEGER (0..4294967295)
    }

    CompoundSha256Condition ::= SEQUENCE {
      fingerprint          OCTET STRING (SIZE(32)),
      cost                 INTEGER (0..4294967295),
      subtypes             ConditionTypes
    }

    ConditionTypes ::= BIT STRING {
      preImageSha256   (0),
      prefixSha256     (1),
      thresholdSha256  (2),
      rsaSha256        (3),
      ed25519Sha256    (4),
      secp256k1Sha256  (5)
    }

    -- Fulfillments

    Fulfillment ::= CHOICE {
      preimageSha256   [0] PreimageFulfillment ,
      prefixSha256     [1] PrefixFulfillment,
      thresholdSha256  [2] ThresholdFulfillment,
      rsaSha256        [3] RsaSha256Fulfillment,
      ed25519Sha256    [4] Ed25519Sha512Fulfillment,
      secp256k1Sha256  [5] Secp256k1Fulfillment
    }

    PreimageFulfillment ::= SEQUENCE {
      preimage             OCTET STRING
    }

    PrefixFulfillment ::= SEQUENCE {
      prefix               OCTET STRING,
      maxMessageLength     INTEGER (0..4294967295),
      subfulfillment       Fulfillment
    }

    ThresholdFulfillment ::= SEQUENCE {
      subfulfillments      SET OF Fulfillment,
      subconditions        SET OF Condition
    }

    RsaSha256Fulfillment ::= SEQUENCE {
      modulus              OCTET STRING,
      signature            OCTET STRING
    }

    Ed25519Sha512Fulfillment ::= SEQUENCE {
      publicKey            OCTET STRING (SIZE(32)),
      signature            OCTET STRING (SIZE(64))
    }

    Secp256k1Fulfillment ::= SEQUENCE {
      publicKey            OCTET STRING (SIZE(33)),
      signature            OCTET STRING (SIZE(64))

    -- Fingerprint Content

    -- The PREIMAGE-SHA-256 condition fingerprint content is not DER encoded
    -- The fingerprint content is the preimage

    PrefixFingerprintContents ::= SEQUENCE {
      prefix               OCTET STRING,
      maxMessageLength     INTEGER (0..4294967295),
      subcondition         Condition
    }

    ThresholdFingerprintContents ::= SEQUENCE {
      threshold            INTEGER (1..65535),
      subconditions2       SET OF Condition
    }

    RsaFingerprintContents ::= SEQUENCE {
      modulus              OCTET STRING
    }

    Ed25519FingerprintContents ::= SEQUENCE {
      publicKey            OCTET STRING (SIZE(32))
    }

    Secp256k1FingerprintContents ::= SEQUENCE {
      publicKey            OCTET STRING (SIZE(33))
    }

END