I'm curently working on a small program to automate decryption in python using PyCryptodome
i have a shell version of my test that work just fine but i can't figure out why it won't verify in python (maybe an encode/decode problem?)
private ECC key generation:
openssl ecparam -name prime256v1 -genkey -noout -out key.pem
public key generation:
openssl ec -in key.pem -pubout -out publicKey.pub
data to sign:
echo test > i_am_a_test.txt
generate sign file:
openssl dgst -sign key.pem -out data.sig i_am_a_test.txt
verify the signature:
openssl dgst -verify publicKey.pub -signature data.sig i_am_a_test.txt
Verified OK
the python version:
import base64
from Crypto.Hash import SHA256
from Crypto.PublicKey import ECC
from Crypto.Signature import DSS
if __name__ == "__main__":
# the pub key from publicKey.pub
pub = "MFkwEwYHKoZIzj0CAQYIKoZIzj0DAQcDQgAEzlNm3snsI8D4VWf7vwNkR4WG0F/ymFgew1xUIVn6tUL0ln lc/lKxOIUa3O2uFkoCUwEALCTpasWbNUoNGi JQ=="
# the data to verify
data = "test"
# the signature from data.sig
sig = "MEYCIQCLbTx5uk18vixVZiG/s9bpBso5u3BZcJDNDSUX5bZc6gIhAMbqzdioGmelKIgVlUmZhtaYs9Szs9asATHCJvTIx7G8"
key = ECC.import_key(base64.b64decode(pub))
h = SHA256.new(base64.b64decode(data))
verifier = DSS.new(key, 'fips-186-3', encoding="der")
verifier.verify(h, base64.b64decode(sig))
print("The message is authentic.")
the verification output
Traceback (most recent call last):
File "/home/admin/Documents/tests/main.py", line 51, in <module>
verifier.verify(h, base64.b64decode(sig))
File "/home/admin/.local/share/virtualenvs/admin-afIRSt_6/lib/python3.8/site-packages/Crypto/Signature/DSS.py", line 169, in verify
raise ValueError("The signature is not authentic")
ValueError: The signature is not authentic
CodePudding user response:
data
is not base64-encoded, but you are trying to decode it before calculating hash.
Also echo
adds an '\n' to the output (try xxd i_am_a_test.txt
), so the data is actually b'test\n'.
import base64
from Crypto.Hash import SHA256
from Crypto.PublicKey import ECC
from Crypto.Signature import DSS
if __name__ == "__main__":
# the pub key from publicKey.pub
pub = "MFkwEwYHKoZIzj0CAQYIKoZIzj0DAQcDQgAEzlNm3snsI8D4VWf7vwNkR4WG0F/ymFgew1xUIVn6tUL0ln lc/lKxOIUa3O2uFkoCUwEALCTpasWbNUoNGi JQ=="
# the data to verify
data = b"test\n"
# the signature from data.sig
sig = "MEYCIQCLbTx5uk18vixVZiG/s9bpBso5u3BZcJDNDSUX5bZc6gIhAMbqzdioGmelKIgVlUmZhtaYs9Szs9asATHCJvTIx7G8"
key = ECC.import_key(base64.b64decode(pub))
h = SHA256.new(data)
verifier = DSS.new(key, 'fips-186-3', encoding="der")
verifier.verify(h, base64.b64decode(sig))
print("The message is authentic.")
Output:
The message is authentic.