def to_key(self, passphrase):
required_length = utils.symmetric_cipher_key_lengths.get(
self.symmetric_algorithm
)
hash_length = utils.hash_lengths.get(self.hash_algorithm)
pass_ = 0
result = bytearray()
# Length of content hashed on each iteration
len2 = len(passphrase) + 8
count = self.count
if count is None:
count = len2
while (pass_ * hash_length) < required_length:
# "If the hash size is less than the key size, multiple instances
# of the hash context are created -- enough to produce the
# required key data."
hash_ = utils.get_hash_instance(self.hash_algorithm)
# "These instances are preloaded with 0, 1, 2, ... octets of zeros
# (that is to say, the first instance has no preloading, the
# second gets preloaded with 1 octet of zero, the third is
# preloaded with two octets of zeros, and so forth)."
hash_.update(bytearray([0x00] * pass_))
# Spec is actually pretty vague here - had to determine when the
# salt really should be hashed from gcrypt/gnupg source.
for i in range(math.ceil(count / float(len2))):
to_write = min(len2, count - (len2 * i))
hash_.update((bytes(self.salt) + bytes(passphrase))[:to_write])
# "Once the passphrase is hashed, the output data from the
# multiple hashes is concatenated, first hash leftmost, to
# produce the key data"
result.extend(bytearray(hash_.digest()))
pass_ += 1
# "any excess octets on the right [are] discarded."
return result[:required_length]
def get_algorithm_and_session_key(self, passphrase):
hash_ = utils.get_hash_instance(self.key_hash_algorithm)
hash_.update(passphrase)
key = hash_.digest()
return 1, key
def get_algorithm_and_session_key(self, passphrase):
hash_ = utils.get_hash_instance(self.key_hash_algorithm)
hash_.update(passphrase)
key = hash_.digest()
return 1, key