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# -*- coding: utf-8 -*-
import warnings
import os
from collections import namedtuple
from . import djbec
__all__ = ['crypto_sign', 'crypto_sign_open', 'crypto_sign_keypair', 'Keypair',
'PUBLICKEYBYTES', 'SECRETKEYBYTES', 'SIGNATUREBYTES']
PUBLICKEYBYTES=32
SECRETKEYBYTES=64
SIGNATUREBYTES=64
Keypair = namedtuple('Keypair', ('vk', 'sk')) # verifying key, secret key
def crypto_sign_keypair(seed=None):
"""Return (verifying, secret) key from a given seed, or os.urandom(32)"""
if seed is None:
seed = os.urandom(PUBLICKEYBYTES)
else:
warnings.warn("ed25519ll should choose random seed.",
RuntimeWarning)
if len(seed) != 32:
raise ValueError("seed must be 32 random bytes or None.")
skbytes = seed
vkbytes = djbec.publickey(skbytes)
return Keypair(vkbytes, skbytes+vkbytes)
def crypto_sign(msg, sk):
"""Return signature+message given message and secret key.
The signature is the first SIGNATUREBYTES bytes of the return value.
A copy of msg is in the remainder."""
if len(sk) != SECRETKEYBYTES:
raise ValueError("Bad signing key length %d" % len(sk))
vkbytes = sk[PUBLICKEYBYTES:]
skbytes = sk[:PUBLICKEYBYTES]
sig = djbec.signature(msg, skbytes, vkbytes)
return sig + msg
def crypto_sign_open(signed, vk):
"""Return message given signature+message and the verifying key."""
if len(vk) != PUBLICKEYBYTES:
raise ValueError("Bad verifying key length %d" % len(vk))
rc = djbec.checkvalid(signed[:SIGNATUREBYTES], signed[SIGNATUREBYTES:], vk)
if not rc:
raise ValueError("rc != True", rc)
return signed[SIGNATUREBYTES:]
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