Digital Signature

Digital Signature

Before digital signature we have to understand the concept of public key encryption.

Public key encryption is asymmetric and uses two separate keys. The security of any encryption scheme depends on length of the key and computation work to break cipher.

A public key encryption scheme has six ingredients:

1.     Plain text:

This is a readable message.

2.     Encryption algorithm:

It performs various transformations on the plain text.

3.     Public and Private key:

This is a pair of keys that has been selected so that if one is used for encryption and other is used for decryption.

4.     Cipher text:

This is the scrambled message that depends on the plain text and key.

5.     Decryption algorithm:

It produces the original plain text.

Public key example:-

Sender à Bob

Receiver à Alice

                                                                                                                                

(i)         Suppose that Bob wants to send a message to Alice and that should be kept secret.

(ii)       In this case Bob uses his own private key to encrypt a message.

(iii)     When Alice receives the cipher text, she finds that she can decrypt the message with the Bob’s private key.

(iv)     So it is proved that the message must have been encrypted by the Bob.

(v)       No one else has Bob’s private key and therefore no one else could have created a cipher text that could be decrypted with Bob’s private key.

(vi)     Therefore entire process is known as digital signature.

It is an authentication mechanism that enables the creator of a message to attach a code that acts as a signature. This signature gratifies the source and integrity of the message.