openmedialibrary_platform/Darwin/lib/python2.7/site-packages/ed25519/keys.py
2014-05-16 01:20:41 +02:00

159 lines
5.6 KiB
Python

import os
import base64
import _ed25519
BadSignatureError = _ed25519.BadSignatureError
def create_keypair(entropy=os.urandom):
SEEDLEN = _ed25519.SECRETKEYBYTES/2
assert SEEDLEN == 32
seed = entropy(SEEDLEN)
sk = SigningKey(seed)
vk = sk.get_verifying_key()
return sk, vk
class BadPrefixError(Exception):
pass
def remove_prefix(s_bytes, prefix):
if not s_bytes.startswith(prefix):
raise BadPrefixError("did not see expected '%s' prefix" % (prefix,))
return s_bytes[len(prefix):]
def to_ascii(s_bytes, prefix="", encoding="base64"):
"""Return a version-prefixed ASCII representation of the given binary
string. 'encoding' indicates how to do the encoding, and can be one of:
* base64
* base32
* base16 (or hex)
This function handles bytes, not bits, so it does not append any trailing
'=' (unlike standard base64.b64encode). It also lowercases the base32
output.
'prefix' will be prepended to the encoded form, and is useful for
distinguishing the purpose and version of the binary string. E.g. you
could prepend 'pub0-' to a VerifyingKey string to allow the receiving
code to raise a useful error if someone pasted in a signature string by
mistake.
"""
if encoding == "base64":
s_ascii = base64.b64encode(s_bytes).rstrip("=")
elif encoding == "base32":
s_ascii = base64.b32encode(s_bytes).rstrip("=").lower()
elif encoding in ("base16", "hex"):
s_ascii = base64.b16encode(s_bytes).lower()
else:
raise NotImplementedError
return prefix+s_ascii
def from_ascii(s_ascii, prefix="", encoding="base64"):
"""This is the opposite of to_ascii. It will throw BadPrefixError if
the prefix is not found.
"""
s_ascii = remove_prefix(s_ascii.strip(), prefix)
if encoding == "base64":
s_ascii += "="*((4 - len(s_ascii)%4)%4)
s_bytes = base64.b64decode(s_ascii)
elif encoding == "base32":
s_ascii += "="*((8 - len(s_ascii)%8)%8)
s_bytes = base64.b32decode(s_ascii.upper())
elif encoding in ("base16", "hex"):
s_bytes = base64.b16decode(s_ascii.upper())
else:
raise NotImplementedError
return s_bytes
class SigningKey(object):
# this can only be used to reconstruct a key created by create_keypair().
def __init__(self, sk_s, prefix="", encoding=None):
assert isinstance(sk_s, type("")) # string, really bytes
sk_s = remove_prefix(sk_s, prefix)
if encoding is not None:
sk_s = from_ascii(sk_s, encoding=encoding)
if len(sk_s) == 32:
# create from seed
vk_s, sk_s = _ed25519.publickey(sk_s)
else:
if len(sk_s) != 32+32:
raise ValueError("SigningKey takes 32-byte seed or 64-byte string")
self.sk_s = sk_s # seed+pubkey
self.vk_s = sk_s[32:] # just pubkey
def to_bytes(self, prefix=""):
return prefix+self.sk_s
def to_ascii(self, prefix="", encoding=None):
assert encoding
return to_ascii(self.to_seed(), prefix, encoding)
def to_seed(self, prefix=""):
return prefix+self.sk_s[:32]
def __eq__(self, them):
if not isinstance(them, object): return False
return (them.__class__ == self.__class__
and them.sk_s == self.sk_s)
def get_verifying_key(self):
return VerifyingKey(self.vk_s)
def sign(self, msg, prefix="", encoding=None):
sig_and_msg = _ed25519.sign(msg, self.sk_s)
# the response is R+S+msg
sig_R = sig_and_msg[0:32]
sig_S = sig_and_msg[32:64]
msg_out = sig_and_msg[64:]
sig_out = sig_R + sig_S
assert msg_out == msg
if encoding:
return to_ascii(sig_out, prefix, encoding)
return prefix+sig_out
class VerifyingKey(object):
def __init__(self, vk_s, prefix="", encoding=None):
assert isinstance(vk_s, type("")) # string, really bytes
vk_s = remove_prefix(vk_s, prefix)
if encoding is not None:
vk_s = from_ascii(vk_s, encoding=encoding)
assert len(vk_s) == 32
self.vk_s = vk_s
def to_bytes(self, prefix=""):
return prefix+self.vk_s
def to_ascii(self, prefix="", encoding=None):
assert encoding
return to_ascii(self.vk_s, prefix, encoding)
def __eq__(self, them):
if not isinstance(them, object): return False
return (them.__class__ == self.__class__
and them.vk_s == self.vk_s)
def verify(self, sig, msg, prefix="", encoding=None):
assert isinstance(sig, type("")) # string, really bytes
if encoding:
sig = from_ascii(sig, prefix, encoding)
else:
sig = remove_prefix(sig, prefix)
assert len(sig) == 64
sig_R = sig[:32]
sig_S = sig[32:]
sig_and_msg = sig_R + sig_S + msg
# this might raise BadSignatureError
msg2 = _ed25519.open(sig_and_msg, self.vk_s)
assert msg2 == msg
def selftest():
message = "crypto libraries should always test themselves at powerup"
sk = SigningKey("priv0-VIsfn5OFGa09Un2MR6Hm7BQ5++xhcQskU2OGXG8jSJl4cWLZrRrVcSN2gVYMGtZT+3354J5jfmqAcuRSD9KIyg",
prefix="priv0-", encoding="base64")
vk = VerifyingKey("pub0-eHFi2a0a1XEjdoFWDBrWU/t9+eCeY35qgHLkUg/SiMo",
prefix="pub0-", encoding="base64")
assert sk.get_verifying_key() == vk
sig = sk.sign(message, prefix="sig0-", encoding="base64")
assert sig == "sig0-E/QrwtSF52x8+q0l4ahA7eJbRKc777ClKNg217Q0z4fiYMCdmAOI+rTLVkiFhX6k3D+wQQfKdJYMxaTUFfv1DQ", sig
vk.verify(sig, message, prefix="sig0-", encoding="base64")
selftest()