95 lines
3.1 KiB
Python
95 lines
3.1 KiB
Python
# MIT License
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#
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# Copyright (c) 2015 Brian Warner and other contributors
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# Permission is hereby granted, free of charge, to any person obtaining a copy
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# of this software and associated documentation files (the "Software"), to deal
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# in the Software without restriction, including without limitation the rights
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# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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# copies of the Software, and to permit persons to whom the Software is
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# furnished to do so, subject to the following conditions:
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#
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# The above copyright notice and this permission notice shall be included in all
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# copies or substantial portions of the Software.
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#
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# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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# SOFTWARE.
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from RNS.Cryptography.Hashes import sha512
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from .basic import (bytes_to_clamped_scalar,
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bytes_to_scalar, scalar_to_bytes,
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bytes_to_element, Base)
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import hashlib, binascii
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def H(m):
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return sha512(m)
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def publickey(seed):
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# turn first half of SHA512(seed) into scalar, then into point
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assert len(seed) == 32
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a = bytes_to_clamped_scalar(H(seed)[:32])
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A = Base.scalarmult(a)
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return A.to_bytes()
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def Hint(m):
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h = H(m)
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return int(binascii.hexlify(h[::-1]), 16)
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def signature(m,sk,pk):
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assert len(sk) == 32 # seed
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assert len(pk) == 32
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h = H(sk[:32])
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a_bytes, inter = h[:32], h[32:]
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a = bytes_to_clamped_scalar(a_bytes)
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r = Hint(inter + m)
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R = Base.scalarmult(r)
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R_bytes = R.to_bytes()
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S = r + Hint(R_bytes + pk + m) * a
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return R_bytes + scalar_to_bytes(S)
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def checkvalid(s, m, pk):
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if len(s) != 64: raise Exception("signature length is wrong")
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if len(pk) != 32: raise Exception("public-key length is wrong")
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R = bytes_to_element(s[:32])
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A = bytes_to_element(pk)
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S = bytes_to_scalar(s[32:])
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h = Hint(s[:32] + pk + m)
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v1 = Base.scalarmult(S)
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v2 = R.add(A.scalarmult(h))
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return v1==v2
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# wrappers
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import os
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def create_signing_key():
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seed = os.urandom(32)
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return seed
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def create_verifying_key(signing_key):
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return publickey(signing_key)
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def sign(skbytes, msg):
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"""Return just the signature, given the message and just the secret
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key."""
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if len(skbytes) != 32:
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raise ValueError("Bad signing key length %d" % len(skbytes))
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vkbytes = create_verifying_key(skbytes)
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sig = signature(msg, skbytes, vkbytes)
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return sig
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def verify(vkbytes, sig, msg):
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if len(vkbytes) != 32:
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raise ValueError("Bad verifying key length %d" % len(vkbytes))
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if len(sig) != 64:
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raise ValueError("Bad signature length %d" % len(sig))
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rc = checkvalid(sig, msg, vkbytes)
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if not rc:
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raise ValueError("rc != 0", rc)
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return True
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