mirror of
https://github.com/trezor/trezor-firmware.git
synced 2024-11-27 09:58:27 +00:00
73 lines
2.9 KiB
Python
73 lines
2.9 KiB
Python
import sys
|
|
from functools import reduce
|
|
import binascii
|
|
from typing import Iterable, Tuple
|
|
|
|
from trezorlib import _ed25519
|
|
|
|
# XXX, these could be NewType's, but that would infect users of the cosi module with these types as well.
|
|
# Unsure if we want that.
|
|
Ed25519PrivateKey = bytes
|
|
Ed25519PublicPoint = bytes
|
|
Ed25519Signature = bytes
|
|
|
|
|
|
def combine_keys(pks: Iterable[Ed25519PublicPoint]) -> Ed25519PublicPoint:
|
|
"""Combine a list of Ed25519 points into a "global" CoSi key."""
|
|
P = [_ed25519.decodepoint(pk) for pk in pks]
|
|
combine = reduce(_ed25519.edwards, P)
|
|
return Ed25519PublicPoint(_ed25519.encodepoint(combine))
|
|
|
|
|
|
def combine_sig(global_R: Ed25519PublicPoint, sigs: Iterable[Ed25519Signature]) -> Ed25519Signature:
|
|
"""Combine a list of signatures into a single CoSi signature."""
|
|
S = [_ed25519.decodeint(si) for si in sigs]
|
|
s = sum(S) % _ed25519.l
|
|
sig = global_R + _ed25519.encodeint(s)
|
|
return Ed25519Signature(sig)
|
|
|
|
|
|
def get_nonce(sk: Ed25519PrivateKey, data: bytes, ctr: int = 0) -> Tuple[int, Ed25519PublicPoint]:
|
|
"""Calculate CoSi nonces for given data.
|
|
These differ from Ed25519 deterministic nonces in that there is a counter appended at end.
|
|
|
|
Returns both the private point `r` and the partial signature `R`.
|
|
`r` is returned for performance reasons: :func:`sign_with_privkey`
|
|
takes it as its `nonce` argument so that it doesn't repeat the `get_nonce` call.
|
|
|
|
`R` should be combined with other partial signatures through :func:`combine_keys`
|
|
to obtain a "global commitment".
|
|
"""
|
|
h = _ed25519.H(sk)
|
|
b = _ed25519.b
|
|
r = _ed25519.Hint(bytes([h[i] for i in range(b >> 3, b >> 2)]) + data + binascii.unhexlify('%08x' % ctr))
|
|
R = _ed25519.scalarmult(_ed25519.B, r)
|
|
return r, Ed25519PublicPoint(_ed25519.encodepoint(R))
|
|
|
|
|
|
def verify(signature: Ed25519Signature, digest: bytes, pub_key: Ed25519PublicPoint) -> None:
|
|
"""Verify Ed25519 signature. Raise exception if the signature is invalid."""
|
|
# XXX this *might* change to bool function
|
|
_ed25519.checkvalid(signature, digest, pub_key)
|
|
|
|
|
|
def pubkey_from_privkey(privkey: Ed25519PrivateKey) -> Ed25519PublicPoint:
|
|
"""Interpret 32 bytes of data as an Ed25519 private key.
|
|
Calculate and return the corresponding public key.
|
|
"""
|
|
return Ed25519PublicPoint(_ed25519.publickey(privkey))
|
|
|
|
|
|
def sign_with_privkey(digest: bytes, privkey: Ed25519PrivateKey,
|
|
global_pubkey: Ed25519PublicPoint,
|
|
nonce: int,
|
|
global_commit: Ed25519PublicPoint) -> Ed25519Signature:
|
|
"""Create a CoSi signature of `digest` with the supplied private key.
|
|
This function needs to know the global public key and global commitment.
|
|
"""
|
|
h = _ed25519.H(privkey)
|
|
b = _ed25519.b
|
|
a = 2 ** (b - 2) + sum(2 ** i * _ed25519.bit(h, i) for i in range(3, b - 2))
|
|
S = (nonce + _ed25519.Hint(global_commit + global_pubkey + digest) * a) % _ed25519.l
|
|
return Ed25519Signature(_ed25519.encodeint(S))
|