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feat: replace _seeds with HKDF #1

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Merged
merged 1 commit into from
Feb 13, 2025
Merged

feat: replace _seeds with HKDF #1

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50 changes: 34 additions & 16 deletions src/nilql/nilql.py
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Original file line number Diff line number Diff line change
Expand Up @@ -8,6 +8,7 @@
import base64
import secrets
import hashlib
import hmac
import bcl
import pailliers

Expand All @@ -23,26 +24,46 @@
_PLAINTEXT_STRING_BUFFER_LEN_MAX = 4096
"""Maximum length of plaintext string values that can be encrypted."""

def _seeds(seed: bytes, index: int) -> bytes:
_Hash = hashlib.sha512
"""Hash function used for HKDF and matching."""


def _hkdf_extract(salt: bytes, input_key: bytes) -> bytes:
"""
Generate entries in an indexed sequence of seeds derived from a base seed.
Extracts a pseudorandom key (PRK) using HMAC with the given salt and input key material.
If the salt is empty, a zero-filled byte string of the same length as the hash function's digest size is used.
"""
if index < 0 or index >= 2 ** 64:
raise ValueError('index must be a 64-bit unsigned integer value')
if len(salt) == 0:
salt = bytes([0] * _Hash().digest_size)
return hmac.new(salt, input_key, _Hash).digest()

return hashlib.sha512(seed + index.to_bytes(8, 'little')).digest()
def _hkdf_expand(pseudo_random_key: bytes, info: bytes, length: int) -> bytes:
"""
Expands the pseudo_random_key into an output key material (OKM) of the desired length using HMAC-based expansion.
"""
t = b""
okm = b""
i = 0
while len(okm) < length:
i += 1
t = hmac.new(pseudo_random_key, t + info + bytes([i]), _Hash).digest()
okm += t
return okm[:length]

def _hkdf(length: int, input_key: bytes, salt: bytes = b"", info: bytes = b"") -> bytes:
"""
Extract a pseudorandom key of `length` from `input_key` and optionally `salt` and `info`.
"""
prk = _hkdf_extract(salt, input_key)
return _hkdf_expand(prk, info, length)

def _random_bytes(length: int, seed: Optional[bytes] = None) -> bytes:
def _random_bytes(length: int, seed: Optional[bytes] = None, salt: Optional[bytes] = None) -> bytes:
"""
Return a random :obj:`bytes` value of the specified length (using
the seed if one is supplied).
"""
if seed is not None:
bytes_ = bytes()
iterations = (length // 64) + (1 if length % 64 > 0 else 0)
for i in range(iterations):
bytes_ = bytes_ + _seeds(seed, i)
return bytes_[:length]
return _hkdf(length, seed, b"" if salt is None else salt)

return secrets.token_bytes(length)

Expand Down Expand Up @@ -72,10 +93,7 @@ def _random_int(
integer = None
index = 0
while integer is None or integer > range_:
bytes_ = bytearray(_random_bytes(
8,
None if seed is None else _seeds(seed, index)
))
bytes_ = bytearray(_random_bytes(8, seed, index.to_bytes(8, 'little')))
index += 1
bytes_[4] &= 1
bytes_[5] &= 0
Expand Down Expand Up @@ -514,7 +532,7 @@ def encrypt(

# Encrypt (i.e., hash) a value for matching.
if key['operations'].get('match'):
ciphertext = _pack(hashlib.sha512(key['material'] + buffer).digest())
ciphertext = _pack(_Hash(key['material'] + buffer).digest())

# If there are multiple nodes, prepare the same ciphertext for each.
if len(key['cluster']['nodes']) > 1:
Expand Down
20 changes: 10 additions & 10 deletions test/test_nilql.py
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Original file line number Diff line number Diff line change
Expand Up @@ -129,12 +129,12 @@ def test_key_from_seed_for_store_with_single_node(self):
sk_from_seed = nilql.SecretKey.generate({'nodes': [{}]}, {'store': True}, SEED)
self.assertEqual(
to_hash_base64(sk_from_seed['material']),
'TVFhJJ32+eh+yaYL1Dhcw7Z+ykY4N1cKDJXDxdS92vI='
'2bW6BLeeCTqsCqrijSkBBPGjDb/gzjtGnFZt0nsZP8w='
)
sk = nilql.SecretKey.generate({'nodes': [{}]}, {'store': True})
self.assertNotEqual(
to_hash_base64(sk['material']),
'TVFhJJ32+eh+yaYL1Dhcw7Z+ykY4N1cKDJXDxdS92vI='
'2bW6BLeeCTqsCqrijSkBBPGjDb/gzjtGnFZt0nsZP8w='
)

def test_key_from_seed_for_store_with_multiple_nodes(self):
Expand All @@ -144,12 +144,12 @@ def test_key_from_seed_for_store_with_multiple_nodes(self):
sk_from_seed = nilql.SecretKey.generate({'nodes': [{}, {}, {}]}, {'store': True}, SEED)
self.assertEqual(
to_hash_base64(sk_from_seed['material']),
'i4ZP5syVY2V6ZFboTey/S83j+7ufgrs4/kUB849/uAI='
'UEoI836rNUBdCixoavnwlPEVqAe2wrPxj+UkVpJPPo0='
)
sk = nilql.SecretKey.generate({'nodes': [{}, {}, {}]}, {'store': True})
self.assertNotEqual(
to_hash_base64(sk['material']),
'i4ZP5syVY2V6ZFboTey/S83j+7ufgrs4/kUB849/uAI='
'UEoI836rNUBdCixoavnwlPEVqAe2wrPxj+UkVpJPPo0='
)

def test_key_from_seed_for_match_with_single_node(self):
Expand All @@ -159,12 +159,12 @@ def test_key_from_seed_for_match_with_single_node(self):
sk_from_seed = nilql.SecretKey.generate({'nodes': [{}]}, {'match': True}, SEED)
self.assertEqual(
to_hash_base64(sk_from_seed['material']),
'M4qqWosTwaBvPMEvUDWKg/RJA3+18+mv/X5Zlj21NhY='
'qbcFGTOGTPo+vs3EChnVUWk5lnn6L6Cr/DIq8li4H+4='
)
sk = nilql.SecretKey.generate({'nodes': [{}]}, {'match': True})
self.assertNotEqual(
to_hash_base64(sk['material']),
'M4qqWosTwaBvPMEvUDWKg/RJA3+18+mv/X5Zlj21NhY='
'qbcFGTOGTPo+vs3EChnVUWk5lnn6L6Cr/DIq8li4H+4='
)

def test_key_from_seed_for_match_with_multiple_nodes(self):
Expand All @@ -174,12 +174,12 @@ def test_key_from_seed_for_match_with_multiple_nodes(self):
sk_from_seed = nilql.SecretKey.generate({'nodes': [{}, {}, {}]}, {'match': True}, SEED)
self.assertEqual(
to_hash_base64(sk_from_seed['material']),
'M4qqWosTwaBvPMEvUDWKg/RJA3+18+mv/X5Zlj21NhY='
'qbcFGTOGTPo+vs3EChnVUWk5lnn6L6Cr/DIq8li4H+4='
)
sk = nilql.SecretKey.generate({'nodes': [{}, {}, {}]}, {'match': True})
self.assertNotEqual(
to_hash_base64(sk['material']),
'M4qqWosTwaBvPMEvUDWKg/RJA3+18+mv/X5Zlj21NhY='
'qbcFGTOGTPo+vs3EChnVUWk5lnn6L6Cr/DIq8li4H+4='
)

def test_key_from_seed_for_sum_with_multiple_nodes(self):
Expand All @@ -189,12 +189,12 @@ def test_key_from_seed_for_sum_with_multiple_nodes(self):
sk_from_seed = nilql.SecretKey.generate({'nodes': [{}, {}, {}]}, {'sum': True}, SEED)
self.assertEqual(
to_hash_base64(sk_from_seed['material']),
'voydliW+MzaYaaIs6ydwLyZdNyYclj+APB2BxNK+AKY='
'l3O25x9CYiiA+XXTNPoT4WylTOXjeWj4GmoSoOPpZHo='
)
sk = nilql.SecretKey.generate({'nodes': [{}, {}, {}]}, {'sum': True})
self.assertNotEqual(
to_hash_base64(sk['material']),
'voydliW+MzaYaaIs6ydwLyZdNyYclj+APB2BxNK+AKY='
'l3O25x9CYiiA+XXTNPoT4WylTOXjeWj4GmoSoOPpZHo='
)

class TestKeysError(TestCase):
Expand Down