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

Class Method Summary collapse

Class Method Details

.h1(msg, context) ⇒ Integer

H1 hash function.

Parameters:

  • msg (String) —

    The message to be hashed.

  • context (FROST::Context) —

    FROST context.

Returns:

  • (Integer) 


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# File 'lib/frost/hash.rb', line 12

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

.h2(msg, context) ⇒ Integer

H2 hash function.

Parameters:

  • msg (String) —

    The message to be hashed.

  • context (FROST::Context) —

    FROST context.

Returns:

  • (Integer) 


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# File 'lib/frost/hash.rb', line 20

def h2(msg, context)
  if context.taproot?
    tagged_hash('BIP0340/challenge', msg)
  else
    hash_to_field(msg, context, "chal")
  end
end

.h3(msg, context) ⇒ Integer

H3 hash function.

Parameters:

  • msg (String) —

    The message to be hashed.

  • context (FROST::Context) —

    FROST context.

Returns:

  • (Integer) 


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# File 'lib/frost/hash.rb', line 32

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

.h4(msg, context) ⇒ String

H4 hash function.

Parameters:

  • msg (String) —

    The message to be hashed.

  • context (FROST::Context) —

    FROST context.

Returns:

  • (String) —

    The hash value.



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# File 'lib/frost/hash.rb', line 40

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

.h5(msg, context) ⇒ String

H5 hash function.

Parameters:

  • msg (String) —

    The message to be hashed.

  • context (FROST::Context) —

    FROST context.

Returns:

  • (String) —

    The hash value.



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# File 'lib/frost/hash.rb', line 48

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

.hash(msg, context, tag) ⇒ Object 



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# File 'lib/frost/hash.rb', line 71

def hash(msg, context, tag)
  raise ArgumentError "context must be FROST::Context." unless context.is_a?(FROST::Context)
  Digest::SHA256.digest(context.ctx_string + tag + msg)
end

.hash_to_field(msg, context, tag) ⇒ Object 



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# File 'lib/frost/hash.rb', line 60

def hash_to_field(msg, context, tag)
  raise ArgumentError "context must be FROST::Context." unless context.is_a?(FROST::Context)
  h2c = case context.group
        when ECDSA::Group::Secp256k1
          H2C.get(H2C::Suite::SECP256K1_XMDSHA256_SSWU_NU_, context.ctx_string + tag)
        when ECDSA::Group::Secp256r1
          H2C.get(H2C::Suite::P256_XMDSHA256_SSWU_NU_, context.ctx_string + tag)
        end
  h2c.hash_to_field(msg, 1, context.group.order).first
end

.hdkg(msg, context) ⇒ Integer

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

Parameters:

  • msg (String) —

    The message to be hashed.

  • context (FROST::Context) —

    FROST context.

Returns:

  • (Integer) —

    The hash value.



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# File 'lib/frost/hash.rb', line 56

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

.tagged_hash(tag, msg) ⇒ Object 



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# File 'lib/frost/hash.rb', line 76

def tagged_hash(tag, msg)
  tag_hash = Digest::SHA256.digest(tag)
  Digest::SHA256.hexdigest(tag_hash + tag_hash + msg).to_i(16)
end