/gdata/Crypto/Hash/HMAC.py
http://radioappz.googlecode.com/ · Python · 108 lines · 48 code · 17 blank · 43 comment · 8 complexity · bb4d0e12154cdb9aeef5dde886ce9b0b MD5 · raw file
- """HMAC (Keyed-Hashing for Message Authentication) Python module.
- Implements the HMAC algorithm as described by RFC 2104.
- This is just a copy of the Python 2.2 HMAC module, modified to work when
- used on versions of Python before 2.2.
- """
- __revision__ = "$Id: HMAC.py,v 1.5 2002/07/25 17:19:02 z3p Exp $"
- import string
- def _strxor(s1, s2):
- """Utility method. XOR the two strings s1 and s2 (must have same length).
- """
- return "".join(map(lambda x, y: chr(ord(x) ^ ord(y)), s1, s2))
- # The size of the digests returned by HMAC depends on the underlying
- # hashing module used.
- digest_size = None
- class HMAC:
- """RFC2104 HMAC class.
- This supports the API for Cryptographic Hash Functions (PEP 247).
- """
- def __init__(self, key, msg = None, digestmod = None):
- """Create a new HMAC object.
- key: key for the keyed hash object.
- msg: Initial input for the hash, if provided.
- digestmod: A module supporting PEP 247. Defaults to the md5 module.
- """
- if digestmod == None:
- import md5
- digestmod = md5
- self.digestmod = digestmod
- self.outer = digestmod.new()
- self.inner = digestmod.new()
- try:
- self.digest_size = digestmod.digest_size
- except AttributeError:
- self.digest_size = len(self.outer.digest())
- blocksize = 64
- ipad = "\x36" * blocksize
- opad = "\x5C" * blocksize
- if len(key) > blocksize:
- key = digestmod.new(key).digest()
- key = key + chr(0) * (blocksize - len(key))
- self.outer.update(_strxor(key, opad))
- self.inner.update(_strxor(key, ipad))
- if (msg):
- self.update(msg)
- ## def clear(self):
- ## raise NotImplementedError, "clear() method not available in HMAC."
- def update(self, msg):
- """Update this hashing object with the string msg.
- """
- self.inner.update(msg)
- def copy(self):
- """Return a separate copy of this hashing object.
- An update to this copy won't affect the original object.
- """
- other = HMAC("")
- other.digestmod = self.digestmod
- other.inner = self.inner.copy()
- other.outer = self.outer.copy()
- return other
- def digest(self):
- """Return the hash value of this hashing object.
- This returns a string containing 8-bit data. The object is
- not altered in any way by this function; you can continue
- updating the object after calling this function.
- """
- h = self.outer.copy()
- h.update(self.inner.digest())
- return h.digest()
- def hexdigest(self):
- """Like digest(), but returns a string of hexadecimal digits instead.
- """
- return "".join([string.zfill(hex(ord(x))[2:], 2)
- for x in tuple(self.digest())])
- def new(key, msg = None, digestmod = None):
- """Create a new hashing object and return it.
- key: The starting key for the hash.
- msg: if available, will immediately be hashed into the object's starting
- state.
- You can now feed arbitrary strings into the object using its update()
- method, and can ask for the hash value at any time by calling its digest()
- method.
- """
- return HMAC(key, msg, digestmod)