How Digital Signatures Work?

If you are not familiar with the basics of cryptography, please read A Note on Cryptography Fundamentals & Algorithms before this. All of them will be used here to explain this.

Involving Process is as follows..

Generate a key pair from sender side

First a key pair has to be generated at the sender side using an Asymmetric Encryption Algorithm like RSA or DSA.

Send the public key to receiver side

Public key has to be sent to the receiver side which is used to decrypt what sender is going to encrypt using his private key.

Get data and compute hash

Now sender get the data which he wants to digitally sign and send to receiver, (ex:- a data packet)
and run a Hashing Algorithm like MD5 or SHA and compute the hash.

Encrypt hash from private key to make signature

Hash /Checksum /Digest is encrypted using the senders private key. This encrypted hash is called the digital signature.

Send Data along with Digital Signature to receiver







Receiver verify the integrity

Now receiver can run the hashing algorithm to compute the hash and he can decrypt the digital signature using the sender's public key and check whether the both hash values are same or not. This way the receiver can find out that the data is really sent by the sender or not.