As we know, there are several Python modules using which we can create or verify DSA digital signatures. The pycryptodome module is an example of one such module. Using this module, one can easily create or verify digital signatures using the following piece of code:

from Crypto.PublicKey import DSA
from Crypto.Hash import SHA256
from Crypto.Signature import DSS

KEYSIZE = 1024
message = "Hello".encode()
key = DSA.generate(KEYSIZE)

publickey = key.publickey()
print(publickey.exportKey())

message_hash = SHA256.new(message)
signer = DSS.new(key, 'fips-186-3')
signature = signer.sign(message_hash)
print(int.from_bytes(signature, "big", signed=False))

verifier = DSS.new(publickey, 'fips-186-3')

try:
    verifier.verify(message_hash, signature)
    print("Verification successful")
except ValueError:
    print("Verification failed")

In our previous article, we have discussed how to implement the DSA key generation algorithm in Python. In this article, we would explain how to implement the DSA signature creation and verification algorithm in Python. We would be using only some common Python modules like the math, or os in our implementation.