Reticulum/RNS/Cryptography/pure25519/eddsa.py

95 lines
3.1 KiB
Python
Raw Normal View History

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