diff options
Diffstat (limited to 'src/common/crypto.py')
| -rw-r--r-- | src/common/crypto.py | 88 |
1 files changed, 43 insertions, 45 deletions
diff --git a/src/common/crypto.py b/src/common/crypto.py index 785b753bb..c787df6aa 100644 --- a/src/common/crypto.py +++ b/src/common/crypto.py @@ -26,82 +26,80 @@ from hashlib import sha256 as SHA256 # convert a large integer to a big-endian bitstring def encode_mpi(n): - if n >= 256: - return encode_mpi(n / 256) + chr(n % 256) - else: - return chr(n) + if n >= 256: + return encode_mpi(n / 256) + chr(n % 256) + else: + return chr(n) # convert a large integer to a big-endian bitstring, padded with \x00s to # a multiple of 16 bytes def encode_mpi_with_padding(n): - return pad_to_multiple(encode_mpi(n), 16, '\x00', True) + return pad_to_multiple(encode_mpi(n), 16, '\x00', True) # pad 'string' to a multiple of 'multiple_of' with 'char'. # pad on the left if 'left', otherwise pad on the right. def pad_to_multiple(string, multiple_of, char, left): - mod = len(string) % multiple_of - if mod == 0: - return string - else: - padding = (multiple_of - mod) * char + mod = len(string) % multiple_of + if mod == 0: + return string + else: + padding = (multiple_of - mod) * char - if left: - return padding + string - else: - return string + padding + if left: + return padding + string + else: + return string + padding # convert a big-endian bitstring to an integer def decode_mpi(s): - if len(s) == 0: - return 0 - else: - return 256 * decode_mpi(s[:-1]) + ord(s[-1]) + if len(s) == 0: + return 0 + else: + return 256 * decode_mpi(s[:-1]) + ord(s[-1]) def sha256(string): - sh = SHA256() - sh.update(string) - return sh.digest() + sh = SHA256() + sh.update(string) + return sh.digest() base28_chr = "acdefghikmopqruvwxy123456789" def sas_28x5(m_a, form_b): - sha = sha256(m_a + form_b + 'Short Authentication String') - lsb24 = decode_mpi(sha[-3:]) - return base28(lsb24) + sha = sha256(m_a + form_b + 'Short Authentication String') + lsb24 = decode_mpi(sha[-3:]) + return base28(lsb24) def base28(n): - if n >= 28: - return base28(n / 28) + base28_chr[n % 28] - else: - return base28_chr[n] + if n >= 28: + return base28(n / 28) + base28_chr[n % 28] + else: + return base28_chr[n] def random_bytes(bytes_): - return os.urandom(bytes_) + return os.urandom(bytes_) def generate_nonce(): - return random_bytes(8) + return random_bytes(8) # generate a random number between 'bottom' and 'top' def srand(bottom, top): - # minimum number of bytes needed to represent that range - bytes = int(math.ceil(math.log(top - bottom, 256))) + # minimum number of bytes needed to represent that range + bytes = int(math.ceil(math.log(top - bottom, 256))) - # in retrospect, this is horribly inadequate. - return (decode_mpi(random_bytes(bytes)) % (top - bottom)) + bottom + # in retrospect, this is horribly inadequate. + return (decode_mpi(random_bytes(bytes)) % (top - bottom)) + bottom # a faster version of (base ** exp) % mod -# taken from <http://lists.danga.com/pipermail/yadis/2005-September/001445.html> +# taken from <http://lists.danga.com/pipermail/yadis/2005-September/001445.html> def powmod(base, exp, mod): - square = base % mod - result = 1 + square = base % mod + result = 1 - while exp > 0: - if exp & 1: # exponent is odd - result = (result * square) % mod + while exp > 0: + if exp & 1: # exponent is odd + result = (result * square) % mod - square = (square * square) % mod - exp /= 2 + square = (square * square) % mod + exp /= 2 - return result - -# vim: se ts=3: + return result |