Digital Signatures

A digital signature is used to validate and ensure authenticity and integrity of the signed file. Digital signatures use public key cryptography encryption method.

Steps in digitally signing a file :-

1. The data to be sent is hashed and a hash value is produced.
2. The hash value is encrypted using sender’s private key and this is called a Digital Signature.
3. The data and digital signature is wrapped and it is called Digitally Signed Data.
4. Then the Digitally Signed Data is sent to the receiver.
5. Receiver breaks down the digitally signed data into data and digital signature.
6. The data is again hashed and a hash value is produced.
7. The digital signature is decrypted using signer’s public key.
8. Then the data hash value and digital signature hash value is cross checked.

If the data hash value and digital signature matches, then the integrity of the file has not been corrupted.

Commonly used Digital Signatures :-

• DSA (Digital Signature Algorithm).
• RSA Signatures.