ABSTRACT:Digital signature is a sort of Cryptography. Cryptography means keeping communications private. It is a practical art of converting messages or data into a different form, such that no one read them without having access to the ‘key’. The message may be converted using a ‘code’ (in which case each character or group of characters is substituted by an alternative one), or ‘cipher’ (in which case the message as a whole is converted, rather than individual characters). It deals with encryption, decryption and authentication.
There are two types of Cryptography-
1.Secret key or Symmetric Cryptography
2. Public key or Asymmetric Cryptography
In Symmetric Cryptography the sender and receiver of a message know and use the same secret key to encrypt the message, and the receiver uses same key to decrypt the message.
Asymmetric (or public key) Cryptography involves two related keys, one of which only the owner knows (the 'private key') and the other which anyone can know (the 'public key').
The advantages of Asymmetric Cryptography are that:
• Only one party needs to know the private key.
• The knowledge of the public key by a third party does not compromise security of message transmission.
The most important development from the work on public –key cryptography is Digital Signature.
REFERENCE:Computer network by Andrew S. Tanenbaum
Cryptography and Network security by William Stallings
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