cert.py 文件源码

def pkcs_i2osp(x,xLen):
    """
    Converts a long (the first parameter) to the associated byte string
    representation of length l (second parameter). Basically, the length
    parameters allow the function to perform the associated padding.

    Input : x        nonnegative integer to be converted
            xLen     intended length of the resulting octet string

    Output: x        corresponding nonnegative integer

    Reverse function is pkcs_os2ip().
    """
    z = number.long_to_bytes(x)
    padlen = max(0, xLen-len(z))
    return '\x00'*padlen + z

# for every hash function a tuple is provided, giving access to 
# - hash output length in byte
# - associated hash function that take data to be hashed as parameter
#   XXX I do not provide update() at the moment.
# - DER encoding of the leading bits of digestInfo (the hash value
#   will be concatenated to create the complete digestInfo).
# 
# Notes:
# - MD4 asn.1 value should be verified. Also, as stated in 
#   PKCS#1 v2.1, MD4 should not be used.
# - hashlib is available from http://code.krypto.org/python/hashlib/
# - 'tls' one is the concatenation of both md5 and sha1 hashes used
#   by SSL/TLS when signing/verifying things