Asymmetric cryptography

Asymmetric cryptography, also known as public-key cryptography, is a cryptographic system that uses pairs of keys: public keys, which may be disseminated widely, and private keys, which are known only to the owner. This accomplishes two functions: authentication, where the public key verifies a holder of the paired private key sent the message, and encryption, where only the paired private key holder can decrypt the message encrypted with the public key.

Overview

In an asymmetric key encryption scheme, anyone can encrypt messages using the public key, but only the holder of the paired private key can decrypt. Security depends on the secrecy of the private key. In the Diffie–Hellman key exchange scheme, each party generates a public/private key pair and distributes the public key. After obtaining an authentic copy of each other's public keys, Alice and Bob can compute a shared secret offline. The shared secret can be used, for instance, as the key in a symmetric cipher.

History

The concept of asymmetric cryptography was first introduced by Whitfield Diffie and Martin Hellman in 1976. Their proposed method, now called Diffie-Hellman key exchange, was revolutionary in that it solved one of the fundamental problems of cryptography: key distribution.

Mathematical foundation

The mathematical foundation of asymmetric cryptography is the computational complexity of several algorithms. The most common are the factorization of large numbers and the calculation of discrete logarithms.

Applications

Asymmetric cryptography is used in numerous applications including secure email, digital signatures, SSL/TLS for securing web traffic, and many more.

See also

• Symmetric cryptography
• Cryptography
• Public-key cryptography
• RSA (cryptosystem)
• Elliptic-curve cryptography