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https://github.com/trezor/trezor-firmware.git
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54f1599a5a
This clarifies the intent: the project is licenced under terms of LGPL version 3 only, but the standard headers cover only "3 or later", so we had to rewrite them. In the same step, we removed author information from individual files in favor of "SatoshiLabs and contributors", and include an AUTHORS file that lists the contributors. Apologies to those whose names are missing; please contact us if you wish to add your info to the AUTHORS file.
89 lines
3.6 KiB
Python
89 lines
3.6 KiB
Python
# This file is part of the Trezor project.
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#
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# Copyright (C) 2012-2018 SatoshiLabs and contributors
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#
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# This library is free software: you can redistribute it and/or modify
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# it under the terms of the GNU Lesser General Public License version 3
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# as published by the Free Software Foundation.
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#
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# This library is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU Lesser General Public License for more details.
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#
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# You should have received a copy of the License along with this library.
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# If not, see <https://www.gnu.org/licenses/lgpl-3.0.html>.
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import sys
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from functools import reduce
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import binascii
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from typing import Iterable, Tuple
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from trezorlib import _ed25519
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# XXX, these could be NewType's, but that would infect users of the cosi module with these types as well.
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# Unsure if we want that.
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Ed25519PrivateKey = bytes
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Ed25519PublicPoint = bytes
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Ed25519Signature = bytes
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def combine_keys(pks: Iterable[Ed25519PublicPoint]) -> Ed25519PublicPoint:
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"""Combine a list of Ed25519 points into a "global" CoSi key."""
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P = [_ed25519.decodepoint(pk) for pk in pks]
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combine = reduce(_ed25519.edwards, P)
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return Ed25519PublicPoint(_ed25519.encodepoint(combine))
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def combine_sig(global_R: Ed25519PublicPoint, sigs: Iterable[Ed25519Signature]) -> Ed25519Signature:
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"""Combine a list of signatures into a single CoSi signature."""
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S = [_ed25519.decodeint(si) for si in sigs]
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s = sum(S) % _ed25519.l
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sig = global_R + _ed25519.encodeint(s)
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return Ed25519Signature(sig)
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def get_nonce(sk: Ed25519PrivateKey, data: bytes, ctr: int = 0) -> Tuple[int, Ed25519PublicPoint]:
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"""Calculate CoSi nonces for given data.
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These differ from Ed25519 deterministic nonces in that there is a counter appended at end.
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Returns both the private point `r` and the partial signature `R`.
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`r` is returned for performance reasons: :func:`sign_with_privkey`
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takes it as its `nonce` argument so that it doesn't repeat the `get_nonce` call.
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`R` should be combined with other partial signatures through :func:`combine_keys`
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to obtain a "global commitment".
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"""
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h = _ed25519.H(sk)
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b = _ed25519.b
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r = _ed25519.Hint(bytes([h[i] for i in range(b >> 3, b >> 2)]) + data + binascii.unhexlify('%08x' % ctr))
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R = _ed25519.scalarmult(_ed25519.B, r)
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return r, Ed25519PublicPoint(_ed25519.encodepoint(R))
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def verify(signature: Ed25519Signature, digest: bytes, pub_key: Ed25519PublicPoint) -> None:
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"""Verify Ed25519 signature. Raise exception if the signature is invalid."""
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# XXX this *might* change to bool function
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_ed25519.checkvalid(signature, digest, pub_key)
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def pubkey_from_privkey(privkey: Ed25519PrivateKey) -> Ed25519PublicPoint:
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"""Interpret 32 bytes of data as an Ed25519 private key.
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Calculate and return the corresponding public key.
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"""
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return Ed25519PublicPoint(_ed25519.publickey(privkey))
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def sign_with_privkey(digest: bytes, privkey: Ed25519PrivateKey,
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global_pubkey: Ed25519PublicPoint,
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nonce: int,
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global_commit: Ed25519PublicPoint) -> Ed25519Signature:
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"""Create a CoSi signature of `digest` with the supplied private key.
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This function needs to know the global public key and global commitment.
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"""
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h = _ed25519.H(privkey)
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b = _ed25519.b
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a = 2 ** (b - 2) + sum(2 ** i * _ed25519.bit(h, i) for i in range(3, b - 2))
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S = (nonce + _ed25519.Hint(global_commit + global_pubkey + digest) * a) % _ed25519.l
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return Ed25519Signature(_ed25519.encodeint(S))
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