src/test/sr_commit_calc_ref.py

   1 # This is a reference implementation of the COMMIT/REVEAL calculation for
   2 # prop250. We use it to generate a test vector for the test_encoding()
   3 # unittest.
   4 #
   5 # Here is the computation formula:
   6 #
   7 #      H = SHA3-256
   8 #      TIMESTAMP = 8 bytes network-endian value
   9 #      RAND = H(32 bytes of random)
  10 #
  11 #      REVEAL = base64-encode( TIMESTAMP || RAND )
  12 #      COMMIT = base64-encode( TIMESTAMP || H(REVEAL) )
  13 #
  14
  15 import sys
  16 import hashlib
  17 import struct
  18 import base64
  19
  20 # Python 3.6+, the SHA3 is available in hashlib natively. Else this requires
  21 # the pysha3 package (pip install pysha3).
  22 if sys.version_info < (3, 6):
  23         import sha3
  24
  25 # Test vector to make sure the right sha3 version will be used. pysha3 < 1.0
  26 # used the old Keccak implementation. During the finalization of SHA3, NIST
  27 # changed the delimiter suffix from 0x01 to 0x06. The Keccak sponge function
  28 # stayed the same. pysha3 1.0 provides the previous Keccak hash, too.
  29 TEST_VALUE = "e167f68d6563d75bb25f3aa49c29ef612d41352dc00606de7cbd630bb2665f51"
  30 if TEST_VALUE != sha3.sha3_256(b"Hello World").hexdigest():
  31   print("pysha3 version is < 1.0. Please install from:")
  32   print("https://github.com/tiran/pysha3https://github.com/tiran/pysha3")
  33   sys.exit(1)
  34
  35 # TIMESTAMP
  36 ts = 1454333590
  37 # RAND
  38 data = 'A' * 32 # Yes very very random, NIST grade :).
  39 rand = hashlib.sha3_256(data)
  40
  41 reveal = struct.pack('!Q', ts) + rand.digest()
  42 b64_reveal = base64.b64encode(reveal)
  43 print("REVEAL: %s" % (b64_reveal))
  44
  45 # Yes we do hash the _encoded_ reveal here that is H(REVEAL)
  46 hashed_reveal = hashlib.sha3_256(b64_reveal)
  47 commit = struct.pack('!Q', ts) + hashed_reveal.digest()
  48 print("COMMIT: %s" % (base64.b64encode(commit)))
  49
  50 # REVEAL: AAAAAFavXpZJxbwTupvaJCTeIUCQmOPxAMblc7ChL5H2nZKuGchdaA==
  51 # COMMIT: AAAAAFavXpbkBMzMQG7aNoaGLFNpm2Wkk1ozXhuWWqL//GynltxVAg==