Digital Signatures

In olden days we used to verify the authenticity and legitimacy of a document using unique Fingerprint or a Signature. But as time changed ,the world shifted towards working with digital documents and data. Now the question arises about digitally signing the data on the internet .

The solution for this problem is a digital signature which is mapped along with the data being sent or received digitally .

One of the famous algorithms of Cryptography - RSA is used to generate digital fingerprints of the data

RSA is a type of public key encryption algorithm which is used to securely transmit data in order to maintain the confidentiality between sender and the receiver.

This algorithm is used in a reversible manner to achieve :

1. Data integrity - verifying that the data remains consistent over its complete lifecycle without being tampered or altered by any external agent.

2. Non-repudiation - verifying the authenticity of the sender, in other words the sender cannot deny that he sent a particular file to someone

Working of the Algorithm

The steps :

1. The first step is the key pair generation using any cryptographic asymmetric algorithms like RSA, AES, DES ..

2. Now the sender has both public and private key , keys are nothing but mathematical entities used in the algorithm for encryption and decryption. The RSA algorithm will be explained in the upcoming blogs .

3. Sender will use any hashing algorithm like SHA256 to hash the data. hashing is a process of converting any form o data to a fixed length of alphanumeric sequence and note that it is irreversible, that is we cannot get the message back from a hash.

4. The resultant hash along with original data is combined together and it is encrypted using the sender's private key. encryption is a process of converting data to a sequence of random alphanumeric characters which doesn't make any sense to read.

5. Now the encrypted data is combined with the sender's public key , this combination is called as the digital signature or the certificate of the sender. Later this data is sent to the receiver.

6. Receiver decrypts the data using sender's public key , he will recover the original data or message along with the hash , if this step is successful then we will achieve Non-repudiation

7. Receiver passes the data to the SHA 256 algorithm and verifies it with the hash received along with the data. If hash is verified we will achieve integrity of data.

Data integrity can be checked if both the hashes match together , this helps us to understand that data is not tampered during transmission.

The identity of the sender can also be verified as data can be decrypted with the public key mapped to the sender.

Hence by using this algorithm we can achieve two important properties of cybersecurity which replicates its behavior with the physical form of the signature.