umbral_pre

Function hash_to_cfrag_verification

Source 
pub fn hash_to_cfrag_verification(
    e: &CurvePoint,
    e1: &CurvePoint,
    e2: &CurvePoint,
    v: &CurvePoint,
    v1: &CurvePoint,
    v2: &CurvePoint,
    u: &CurvePoint,
    u1: &CurvePoint,
    u2: &CurvePoint,
) -> NonZeroCurveScalar
Expand description

Calculates the challenge scalar for the proof of reencryption.

Note: this function is only public for documenting purposes (see ReencryptionEvidence).

Calculated as the SHA256 hash of the concatenation of (the points are represented in the compressed form, 33 bytes each):

  • 0x00000012 (4 bytes, the length of the DST)
  • b"CFRAG_VERIFICATION" (18 bytes)
  • Capsule::e
  • CapsuleFrag::e1
  • CapsuleFrag::e2
  • Capsule::v
  • CapsuleFrag::v1
  • CapsuleFrag::v2
  • Parameters::u
  • CapsuleFrag::u1
  • CapsuleFrag::u2

The hash (32 bytes) is then treated as the big-endian representation of an integer, and converted to a non-zero curve scalar by taking the modulo of p - 1 and adding 1, where p is the secp256k1 order.

The points mentioned above are the same as in the return values of Capsule::to_bytes_simple and CapsuleFrag::to_bytes_simple.