Checking Equality of Hashes

gistfile1.py

def is_equal(val1, val2):
    """
    This is a really nice way to comparing two hash values using the set operation XOR
    
    This snippet is from the plone project https://github.com/plone/plone.session/blob/master/plone/session/tktauth.py
    """

    # constant time comparison
    if not isinstance(val1, basestring) or not isinstance(val2, basestring):
        return False
    if len(val1) != len(val2):
        return False
    result = 0
    for x, y in zip(val1, val2):
        result |= ord(x) ^ ord(y) # XOR i.e. returns the set of all of the values not shared between x and y
    return result == 0 # the result set should be 0