Recovering A Message From Just A Signature

Remember those times when you used to sign for things physically? That strip on the back of your credit card, for example, used to be so important for checking your purchases. These days, few of us need to sign for things physically, and often for legal purposes, we even use a fake version of our signature. But, imagine if when you physically signed a document, then the signature would actually contain the details of the document. Well, in a digital world, we can do this with the ElGamal signature method.

Message Recovery from a digital signature

We normally use digital signatures to sign a message, and where the message is also defined alongside the signature. Alice will sign the message with her private key and then proves the signature with her public key. Within the Nyberg-Rueppel method, we use ElGamal encryption and can recover the message from the signature [1]:

In this case, the message is a value of 10, and we generate private and public keys of various sizes.

In this method, we generate two prime numbers p and q and make sure that q is a divisor of p−1. Next, we compute a value of α and a…