ASSYMETRICAL KEY

• The need for alternative to private key encryption
• Early Development of Alternative Key Exchange Mechanism
• Development of Asymmetrical Key Encryption

The need for alternative to private key encryption

Public key encryption was invented in 1976 to circumvent the problems of managing the private key. The whole point of encryption is to keep messages private. At that point, all you could do was encrypt the message with a key, and get both the encrypted message and the key to the target person. The US government found a rather expensive solution to this problem. Keys were sent via couriers, in briefcases handcuffed to their arms. If a courier did not arrive, then all messages on that key would be destroyed, and another courier would be sent again.

Public key encryption is also known as asymmetric key encryption. It uses different keys to encrypt and decrypt a message. Under this system everyone gets a pair of keys: a public key which is published for all to see and use, and a private key which is to be kept secret. The public key could then be used to encrypt a message, which only the holder of the private key, could decrypt and read.

The private key never gets transmitted, so there are no problems associated with symmetric key encryption. Furthermore, public key encryption can be used for authentication via the digital signature mechanism. In this sense, asymmetric key is particularly strong in authentication. Message is not only protected in terms of secrecy, but also in integrity.

Public key, or asymmetric key encryption, ciphers generally require longer keys than symmetric ciphers to achieve the same level of security. Comparing key lengths between different encryption algorithms is not particularly productive as the different algorithms have different characteristics.