Module: Drand::Verifier

Defined in:
lib/drand/verifier.rb

Constant Summary collapse

UNCHAINED_G1 = 
"bls-unchained-g1-rfc9380"
CHAINED_G2 = 
"pedersen-bls-chained"
SUPPORTED_SCHEMES = 
[UNCHAINED_G1, CHAINED_G2].freeze

Class Method Summary collapse

Class Method Details

.round_bytes(round) ⇒ Object 



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# File 'lib/drand/verifier.rb', line 55

def round_bytes(round)
  [round].pack("Q>")
end

.verify(scheme:, public_key:, round:, signature:, previous_signature: nil) ⇒ Object 



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# File 'lib/drand/verifier.rb', line 17

def verify(scheme:, public_key:, round:, signature:, previous_signature: nil)
  raise VerificationError, "scheme is required" if scheme.nil? || scheme.empty?
  raise VerificationError, "public_key is required" if public_key.nil? || public_key.empty?
  raise VerificationError, "signature is required" if signature.nil? || signature.empty?
  raise VerificationError, "round must be a positive Integer" unless round.is_a?(Integer) && round.positive?

  case scheme
  when UNCHAINED_G1
    verify_unchained_g1(public_key, round, signature)
  when CHAINED_G2
    verify_chained_g2(public_key, round, signature, previous_signature)
  else
    raise VerificationError, "unsupported scheme #{scheme.inspect}"
  end
rescue BLS::Error, BLS::PointError => e
  raise VerificationError, "BLS error: #{e.message}"
rescue ::ArgumentError => e
  raise VerificationError, "invalid hex input: #{e.message}"
end

.verify_chained_g2(public_key_hex, round, signature_hex, previous_signature_hex) ⇒ Object 



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# File 'lib/drand/verifier.rb', line 44

def verify_chained_g2(public_key_hex, round, signature_hex, previous_signature_hex)
  if previous_signature_hex.nil? || previous_signature_hex.empty?
    raise VerificationError, "chained scheme requires previous_signature"
  end
  prev_bytes = [previous_signature_hex].pack("H*")
  msg = Digest::SHA256.hexdigest(prev_bytes + round_bytes(round))
  sig = BLS::PointG2.from_hex(signature_hex)
  pk  = BLS::PointG1.from_hex(public_key_hex)
  BLS.verify(sig, msg, pk)
end

.verify_unchained_g1(public_key_hex, round, signature_hex) ⇒ Object 



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# File 'lib/drand/verifier.rb', line 37

def verify_unchained_g1(public_key_hex, round, signature_hex)
  msg = Digest::SHA256.hexdigest(round_bytes(round))
  sig = BLS::PointG1.from_hex(signature_hex)
  pk  = BLS::PointG2.from_hex(public_key_hex)
  BLS.verify(sig, msg, pk)
end