src/test/sr_srv_calc_ref.py

   1 # This is a reference implementation of the SRV calculation for prop250. We
   2 # use it to generate a test vector for the test_sr_compute_srv() unittest.
   3 # (./test shared-random/sr_compute_srv)
   4 #
   5 # Here is the SRV computation formula:
   6 #
   7 #      HASHED_REVEALS = H(ID_a | R_a | ID_b | R_b | ..)
   8 #
   9 #      SRV = SHA3-256("shared-random" | INT_8(reveal_num) | INT_4(version) |
  10 #                     HASHED_REVEALS | previous_SRV)
  11 #
  12
  13 import sys
  14 import hashlib
  15 import struct
  16
  17 # Python 3.6+, the SHA3 is available in hashlib natively. Else this requires
  18 # the pysha3 package (pip install pysha3).
  19 if sys.version_info < (3, 6):
  20         import sha3
  21
  22 # Test vector to make sure the right sha3 version will be used. pysha3 < 1.0
  23 # used the old Keccak implementation. During the finalization of SHA3, NIST
  24 # changed the delimiter suffix from 0x01 to 0x06. The Keccak sponge function
  25 # stayed the same. pysha3 1.0 provides the previous Keccak hash, too.
  26 TEST_VALUE = "e167f68d6563d75bb25f3aa49c29ef612d41352dc00606de7cbd630bb2665f51"
  27 if TEST_VALUE != sha3.sha3_256(b"Hello World").hexdigest():
  28   print("pysha3 version is < 1.0. Please install from:")
  29   print("https://github.com/tiran/pysha3https://github.com/tiran/pysha3")
  30   sys.exit(1)
  31
  32 # In this example, we use three reveal values.
  33 reveal_num = 3
  34 version = 1
  35
  36 # We set directly the ascii value because memset(buf, 'A', 20) makes it to 20
  37 # times "41" in the final string.
  38
  39 # Identity and reveal value of dirauth a
  40 ID_a = 20 * "41" # RSA identity of 40 base16 bytes.
  41 R_a = 56 * 'A' # 56 base64 characters
  42
  43 # Identity and reveal value of dirauth b
  44 ID_b = 20 * "42" # RSA identity of 40 base16 bytes.
  45 R_b = 56 * 'B' # 56 base64 characters
  46
  47 # Identity and reveal value of dirauth c
  48 ID_c = 20 * "43" # RSA identity of 40 base16 bytes.
  49 R_c = 56 * 'C' # 56 base64 characters
  50
  51 # Concatenate them all together and hash them to form HASHED_REVEALS.
  52 REVEALS = (ID_a + R_a + ID_b + R_b + ID_c + R_c).encode()
  53 hashed_reveals_object = hashlib.sha3_256(REVEALS)
  54 hashed_reveals = hashed_reveals_object.digest()
  55
  56 previous_SRV = (32 * 'Z').encode()
  57
  58 # Now form the message.
  59 #srv_msg = struct.pack('13sQL256ss', "shared-random", reveal_num, version,
  60 #                      hashed_reveals, previous_SRV)
  61 invariant_token = b"shared-random"
  62 srv_msg = invariant_token + \
  63           struct.pack('!QL', reveal_num, version) + \
  64           hashed_reveals + \
  65           previous_SRV
  66
  67 # Now calculate the HMAC
  68 srv = hashlib.sha3_256(srv_msg)
  69 print("%s" % srv.hexdigest().upper())
  70
  71 # 2A9B1D6237DAB312A40F575DA85C147663E7ED3F80E9555395F15B515C74253D