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Digital Signatures in Cryptography

Cryptography | Digital Signatures: In this tutorial, we will learn about digital signatures briefly and will then look into the different applications of digital signatures. We will have a brief explanation about each of them, regarding their way of functioning and the ways by which they are implemented in various encryption techniques. By Monika Sharma Last updated : May 25, 2023

What is Digital Signature in Cryptography?

A signature is usually used to bind signatory to the message. The digital signature is thus a technique that binds a person or the entity to the digital data. This binding ensures that the person sending the data is solely responsible for being for it and this binding can be verified by the receiver and the third party. This digital signature is also stored using hash functions so that no one’s signature can be stolen and be misused. The process of binding the data with the digital signature is as follows.

Process of binding the data with a digital signature

The user or the person who is sending the data is asked to enter some signature. This can be any unique text or his identity or something else. Hash Function is applied over this signature value and it is attached to the message being sent. The message is then transmitted to the other user with the hash value of the signature. The receiver then checks for the similarity between the signatory values. In this way, a digital signature is applied over the digital data.

Applications of digital signature

The following are the applications of digital signature:

1. Message Authentication: When the verifier validates the digital signature using the public key, he is assured that the signature has been created by the valid sender who is having the private key. In this way, the receiver is assured that the message is sent by the one whose signature is attached with the message and this implies the message authentication.
2. Data Integrity: In case the data has been modified in between the transmission, the signature verification algorithm fails at the receiver’s side. The hash code of the modified data and the output provided by the verification algorithm will no match, so the receiver can safely deny the message assuming that the data integrity has not been reached.
3. Non- Repudiation: The sender cannot deny that he has not sent that data if the data has been attached to the digital signature of the sender. Since, the person who is attaching the signature with the data that is to be transmitted, is the only person who can create that unique signature for his data (unless his signature is stolen by someone else), the receiver can present the data along with the digital signature in case the sender denies that he has not sent that data. Therefore, the signature must be kept private and must not be shared with anyone.
   Example, whenever a mail is received, the email id of the sender is the signatory to the message, and as every email id is unique, in case if any message is sent using his email address, the sender cannot deny from the fact that he has not sent that mail.