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pyca
AES-SIV does not accept empty plaintext.
This issue is possibly related to #10808, which observes a similar behavior for AES-GCM-SIV.
I'm using python version 3.12.3 and cryptography version 42.0.5
The following code
from cryptography.hazmat.primitives.ciphers import aead
import cryptography
import sys
def test_empty_pt():
key = bytes(range(32))
nonce = bytes(range(12))
pt = b""
aads = [b"row1", b"col2", b"timestamp"]
crypter = aead.AESSIV(key)
ct = crypter.encrypt(pt, aads)
if __name__ == "__main__":
print(f"{sys.version=}")
print(f"{cryptography.__version__=}")
test_empty_pt()
gives the following result:
sys.version='3.12.3 (tags/v3.12.3:f6650f9, Apr 9 2024, 14:05:25) [MSC v.1938 64 bit (AMD64)]' cryptography.version='42.0.5' Traceback (most recent call last): File ".../aes_siv_test.py", line 16, in
test_empty_pt() File ".../aes_siv_test.py", line 11, in test_empty_pt ct = crypter.encrypt(pt, aads) ValueError: data must not be zero length
The only restriction I could find is RFC 5297, section 6, where there is a lower bound of 1 byte for the nonce, when AES-SIV is being used as AEAD. However, AES-SIV is useful in many contexts, e.g., deterministically encrypting cells in a database using row and column as AAD. For such uses it would be helpful if all fields can be empty.
Without being at a computer to test, this almost certainly is for the same reason -- n Limitations in OpenSSL
On Tue, May 7, 2024, 2:03 PM bleichenbacher-daniel @.***> wrote:
This issue is possibly related to #10808 https://github.com/pyca/cryptography/issues/10808, which observes a similar behavior for AES-GCM-SIV.
I'm using python version 3.12.3 and cryptography version 42.0.5
The following code
from cryptography.hazmat.primitives.ciphers import aead import cryptography import sys
def test_empty_pt(): key = bytes(range(32)) nonce = bytes(range(12)) pt = b"" aads = [b"row1", b"col2", b"timestamp"] crypter = aead.AESSIV(key) ct = crypter.encrypt(pt, aads)
if name == "main": print(f"{sys.version=}") print(f"{cryptography.version=}") test_empty_pt()
gives the following result:
sys.version='3.12.3 (tags/v3.12.3:f6650f9, Apr 9 2024, 14:05:25) [MSC v.1938 64 bit (AMD64)]' cryptography.version='42.0.5' Traceback (most recent call last): File ".../aes_siv_test.py", line 16, in test_empty_pt() File ".../aes_siv_test.py", line 11, in test_empty_pt ct = crypter.encrypt(pt, aads) ValueError: data must not be zero length
The only restriction I could find is RFC 5297, section 6, where there is a lower bound of 1 byte for the nonce, when AES-SIV is being used as AEAD. However, AES-SIV is useful in many contexts, e.g., deterministically encrypting cells in a database using row and column as AAD. For such uses it would be helpful if all fields can be empty.
— Reply to this email directly, view it on GitHub https://github.com/pyca/cryptography/issues/10958, or unsubscribe https://github.com/notifications/unsubscribe-auth/AAAAGBDMFSUFJHDMLCESKQLZBEJOZAVCNFSM6AAAAABHLPMXPOVHI2DSMVQWIX3LMV43ASLTON2WKOZSGI4DGOJTGI4TGNQ . You are receiving this because you are subscribed to this thread.Message ID: @.***>
