def digest(self):
if self._digest is None:
h1 = self.h.digest()
del self.h
h2 = SHA256(h1).digest()
if self.truncate_to:
h2 = h2[:self.truncate_to]
self._digest = h2
return self._digest
def __init__(self, truncate_to=None):
self.h = SHA256()
self.truncate_to = truncate_to
self._digest = None
def hmac(tag, data):
ikey = _xor(tag, "\x36")
okey = _xor(tag, "\x5c")
h1 = SHA256(ikey + data).digest()
h2 = SHA256(okey + h1).digest()
return h2