Digital Signature

Digital Signature RSA256 Algorithm (Python)

#How To - perform a digital signature using RSA256 algorithm in Python

##Step 1 - generate an RSA256 key pair (public and private keys) using the command module <Crypto.PublicKey.RSA> to generate the key pair.
from Crypto.PublicKey import RSA

key = RSA.generate(2048)
public_key = key.publickey()
print(public_key) #not sure if I need this here but I want to see the output 


##Step 2 - use the private key to sign an input message.
from Crypto.Signature import PKCS1_v1_5
from Crypto.Hash import SHA256

message = b'This is a message to be signed'
hash = SHA256.new(message)
print(message) #to see the output 

signer = PKCS1_v1_5.new(key)
signature = signer.sign(hash)
print(signer) #to see the output
print(signature) #to see the output


##Step 4 - use the public key to verify the signature
verifier = PKCS1_v1_5.new(public_key)
if verifier.verify(hash, signature):
    print("The signature is authentic.")
else:
    print("The signature is not authentic.")


#If you need to sign a longer chain of text/ message, use a hash function to generate a fixed-length hash of the message, then sign it.

Further Reading. - Cryptography
https://pymotw.com/3/hmac/index.html
https://pymotw.com/3/hashlib/index.html