72 lines
2.5 KiB
Python
72 lines
2.5 KiB
Python
# This is a reference implementation of the SRV calculation for prop250. We
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# use it to generate a test vector for the test_sr_compute_srv() unittest.
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# (./test shared-random/sr_compute_srv)
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#
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# Here is the SRV computation formula:
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#
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# HASHED_REVEALS = H(ID_a | R_a | ID_b | R_b | ..)
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#
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# SRV = SHA3-256("shared-random" | INT_8(reveal_num) | INT_4(version) |
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# HASHED_REVEALS | previous_SRV)
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#
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import sys
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import hashlib
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import struct
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# Python 3.6+, the SHA3 is available in hashlib natively. Else this requires
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# the pysha3 package (pip install pysha3).
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if sys.version_info < (3, 6):
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import sha3
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# Test vector to make sure the right sha3 version will be used. pysha3 < 1.0
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# used the old Keccak implementation. During the finalization of SHA3, NIST
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# changed the delimiter suffix from 0x01 to 0x06. The Keccak sponge function
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# stayed the same. pysha3 1.0 provides the previous Keccak hash, too.
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TEST_VALUE = "e167f68d6563d75bb25f3aa49c29ef612d41352dc00606de7cbd630bb2665f51"
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if TEST_VALUE != sha3.sha3_256(b"Hello World").hexdigest():
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print("pysha3 version is < 1.0. Please install from:")
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print("https://github.com/tiran/pysha3https://github.com/tiran/pysha3")
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sys.exit(1)
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# In this example, we use three reveal values.
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reveal_num = 3
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version = 1
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# We set directly the ascii value because memset(buf, 'A', 20) makes it to 20
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# times "41" in the final string.
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# Identity and reveal value of dirauth a
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ID_a = 20 * "41" # RSA identity of 40 base16 bytes.
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R_a = 56 * 'A' # 56 base64 characters
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# Identity and reveal value of dirauth b
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ID_b = 20 * "42" # RSA identity of 40 base16 bytes.
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R_b = 56 * 'B' # 56 base64 characters
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# Identity and reveal value of dirauth c
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ID_c = 20 * "43" # RSA identity of 40 base16 bytes.
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R_c = 56 * 'C' # 56 base64 characters
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# Concatenate them all together and hash them to form HASHED_REVEALS.
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REVEALS = (ID_a + R_a + ID_b + R_b + ID_c + R_c).encode()
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hashed_reveals_object = hashlib.sha3_256(REVEALS)
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hashed_reveals = hashed_reveals_object.digest()
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previous_SRV = (32 * 'Z').encode()
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# Now form the message.
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#srv_msg = struct.pack('13sQL256ss', "shared-random", reveal_num, version,
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# hashed_reveals, previous_SRV)
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invariant_token = b"shared-random"
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srv_msg = invariant_token + \
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struct.pack('!QL', reveal_num, version) + \
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hashed_reveals + \
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previous_SRV
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# Now calculate the HMAC
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srv = hashlib.sha3_256(srv_msg)
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print("%s" % srv.hexdigest().upper())
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# 2A9B1D6237DAB312A40F575DA85C147663E7ED3F80E9555395F15B515C74253D
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