23 June 2010

Digital Signatures

Digital Signatures
Basically Network Security has four aspects that are integrity, privacy, authentication, non-repudiation.
Of all these Digital signatures covers three ie integrity,authentication and non-repudiatation.
Most of websites such as paypal.com, amazon.com and many more use these techniques for authentication of user
Say, you have some message or a file.
You want to send it to some place, now receiver wants some mechanism so that it can ensure that message that it has received is sent by intended user
Now question is how?
So for that we use concept of digital signatures
Here we use RSA asymmetric encryption/decryption algorithm where there are two keys named public key which is publically distributed and private key is kept secret
But since this algorithm is suitable for only short messages, so we generate digest of that message.
We use either MD5 or SHA1 algorithms to generate digest of the message.
Now the generated digest is then encrypted by sender by using his own private key, the encrypted digest is then appended with original message and send towards receiver.
Now at receiver side, it performs three steps
1:- decrypt the digest and retrieves the original digest.
2:-Generates a digest from original message.
3:-Compares both if both are same then it means message is sent by intended user
Hence it authenticates the user.
Diagrammatic representation of the whole procedure:-

At Sender side:-

At Receiver side:-

if both matched then it means user is authenticated else the message is rejected

Note :-Keeping visiting blog for code of this whole procedure in java

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