Module: FROST::Hash

Defined in:
lib/frost/hash.rb

Overview

Cryptographic hash function using FROST. www.ietf.org/archive/id/draft-irtf-cfrg-frost-15.html#name-cryptographic-hash-function

Constant Summary collapse

CTX_STRING_SECP256K1 = 
"FROST-secp256k1-SHA256-v1"
CTX_STRING_P256 = 
"FROST-P256-SHA256-v1"

Class Method Summary collapse

Class Method Details

.h1(msg, group) ⇒ Integer

H1 hash function. param [ECDSA::Group] group The elliptic curve group.

Parameters:

  • msg (String) —

    The message to be hashed.

Returns:

  • (Integer) 


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# File 'lib/frost/hash.rb', line 15

def h1(msg, group)
  hash_to_field(msg, group, "rho")
end

.h2(msg, group) ⇒ Integer

H3 hash function.

Parameters:

  • msg (String) —

    The message to be hashed.

  • group (ECDSA::Group) —

    The elliptic curve group.

Returns:

  • (Integer) 


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# File 'lib/frost/hash.rb', line 23

def h2(msg, group)
  hash_to_field(msg, group, "chal")
end

.h3(msg, group) ⇒ Integer

H3 hash function.

Parameters:

  • msg (String) —

    The message to be hashed.

  • group (ECDSA::Group) —

    The elliptic curve group.

Returns:

  • (Integer) 


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# File 'lib/frost/hash.rb', line 31

def h3(msg, group)
  hash_to_field(msg, group, "nonce")
end

.h4(msg, group) ⇒ String

H4 hash function.

Parameters:

  • msg (String) —

    The message to be hashed.

  • group (ECDSA::Group) —

    The elliptic curve group.

Returns:

  • (String) —

    The hash value.



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# File 'lib/frost/hash.rb', line 39

def h4(msg, group)
  hash(msg, group, "msg")
end

.h5(msg, group) ⇒ String

H5 hash function.

Parameters:

  • msg (String) —

    The message to be hashed.

  • group (ECDSA::Group) —

    The elliptic curve group.

Returns:

  • (String) —

    The hash value.



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# File 'lib/frost/hash.rb', line 47

def h5(msg, group)
  hash(msg, group, "com")
end

.hash(msg, group, context) ⇒ Object 



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# File 'lib/frost/hash.rb', line 72

def hash(msg, group, context)
  case group
  when ECDSA::Group::Secp256k1
    Digest::SHA256.digest(CTX_STRING_SECP256K1 + context + msg)
  when ECDSA::Group::Secp256r1
    Digest::SHA256.digest(CTX_STRING_P256 + context + msg)
  else
    # TODO support other suite.
    raise RuntimeError, "group #{group} dose not supported."
  end
end

.hash_to_field(msg, group, context) ⇒ Object 



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# File 'lib/frost/hash.rb', line 59

def hash_to_field(msg, group, context)
  h2c = case group
        when ECDSA::Group::Secp256k1
          H2C.get(H2C::Suite::SECP256K1_XMDSHA256_SSWU_NU_, CTX_STRING_SECP256K1 + context)
        when ECDSA::Group::Secp256r1
          H2C.get(H2C::Suite::P256_XMDSHA256_SSWU_NU_, CTX_STRING_P256 + context)
        else
          # TODO support other suite.
          raise RuntimeError, "group #{group} dose not supported."
        end
  h2c.hash_to_field(msg, 1, group.order).first
end

.hdkg(msg, group) ⇒ Integer

Hash function for a FROST ciphersuite, used for the DKG.

Parameters:

  • msg (String) —

    The message to be hashed.

  • group (ECDSA::Group) —

    The elliptic curve group.

Returns:

  • (Integer) —

    The hash value.



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# File 'lib/frost/hash.rb', line 55

def hdkg(msg, group)
  hash_to_field(msg, group, "dkg")
end