def stream_decrypt(self, salt, ciphertext):
"""Decrypt ciphertext with given salt, return (preprocessed) word."""
left_ciphertext = self.left_part(ciphertext)
stream_prefix = self.stream_prefix(salt)
left_part = crypto.xor(left_ciphertext, stream_prefix)
word_key = self.word_key(left_part)
stream_suffix = self.stream_suffix(word_key, stream_prefix)
return crypto.xor(ciphertext, stream_prefix + stream_suffix)
def stream_decrypt(self, salt, ciphertext):
"""Decrypt ciphertext with given salt, return (preprocessed) word."""
left_ciphertext = self.left_part(ciphertext)
stream_prefix = self.stream_prefix(salt)
left_part = crypto.xor(left_ciphertext, stream_prefix)
word_key = self.word_key(left_part)
stream_suffix = self.stream_suffix(word_key, stream_prefix)
return crypto.xor(ciphertext, stream_prefix + stream_suffix)
def stream_encrypt(self, salt, preword):
"""Encrypt a (preprocessed) word with given salt."""
left_part = self.left_part(preword)
word_key = self.word_key(left_part)
stream_prefix = self.stream_prefix(salt)
stream_suffix = self.stream_suffix(word_key, stream_prefix)
return crypto.xor(preword, stream_prefix + stream_suffix)
def stream_encrypt(self, salt, preword):
"""Encrypt a (preprocessed) word with given salt."""
left_part = self.left_part(preword)
word_key = self.word_key(left_part)
stream_prefix = self.stream_prefix(salt)
stream_suffix = self.stream_suffix(word_key, stream_prefix)
return crypto.xor(preword, stream_prefix + stream_suffix)
def match(b64field, b64query):
"""Return True if the given query matches the field.
Parameters:
b64field -- a concatenation of salt and ciphertext, each BLOCK_BYTES long,
encoded in base64
b64query -- a concatenation of preword and word_key, each BLOCK_BYTES long,
encoded in base64
"""
# Ensure byte strings.
if isinstance(b64field, str):
b64field = str.encode(b64field)
elif not isinstance(b64field, (bytes, bytearray)):
return False
if isinstance(b64query, str):
b64query = str.encode(b64query)
elif not isinstance(b64query, (bytes, bytearray)):
print('bad instance', type(b64query), b64query)
return False
# Decode from base64.
try:
field = base64.decodebytes(b64field)
query = base64.decodebytes(b64query)
except:
return False
# Require correct sizes.
if len(query) != 2 * BLOCK_BYTES or len(field) != 2 * BLOCK_BYTES:
return False
# Check using Song et al.'s Final Scheme.
preword, word_key = query[:BLOCK_BYTES], query[BLOCK_BYTES:]
_, ciphertext = field[:BLOCK_BYTES], field[BLOCK_BYTES:]
block = crypto.xor(ciphertext, preword)
prefix, suffix = block[:LEFT_BYTES], block[LEFT_BYTES:]
hashed_prefix = crypto.prfunction(word_key, prefix, length=MATCH_BYTES)
return hashed_prefix == suffix
def match(b64field, b64query):
"""Return True if the given query matches the field.
Parameters:
b64field -- a concatenation of salt and ciphertext, each BLOCK_BYTES long,
encoded in base64
b64query -- a concatenation of preword and word_key, each BLOCK_BYTES long,
encoded in base64
"""
# Ensure byte strings.
if isinstance(b64field, str):
b64field = str.encode(b64field)
elif not isinstance(b64field, (bytes, bytearray)):
return False
if isinstance(b64query, str):
b64query = str.encode(b64query)
elif not isinstance(b64query, (bytes, bytearray)):
print('bad instance', type(b64query), b64query)
return False
# Decode from base64.
try:
field = base64.decodebytes(b64field)
query = base64.decodebytes(b64query)
except:
return False
# Require correct sizes.
if len(query) != 2 * BLOCK_BYTES or len(field) != 2 * BLOCK_BYTES:
return False
# Check using Song et al.'s Final Scheme.
preword, word_key = query[:BLOCK_BYTES], query[BLOCK_BYTES:]
_, ciphertext = field[:BLOCK_BYTES], field[BLOCK_BYTES:]
block = crypto.xor(ciphertext, preword)
prefix, suffix = block[:LEFT_BYTES], block[LEFT_BYTES:]
hashed_prefix = crypto.prfunction(word_key, prefix, length=MATCH_BYTES)
return hashed_prefix == suffix
def test_xor(self):
test_block = b"t" * constants.BLOCK_BYTES
null_block = b"\0" * constants.BLOCK_BYTES
self.assertEqual(crypto.xor(null_block, test_block), test_block)
self.assertEqual(crypto.xor(test_block, test_block), null_block)
