An asymmetric algorithm makes use of different keys for encryption and decryption. Of the two keys, one is to be kept secret (private key) and the other may be published for all to see (public key). The derivation of the private key from the public key should be computationally infeasible. Some example uses of asymmetric algorithms are to be found in the areas of public key encryption and digital signing.
The opposite of the asymmetric algorithm is the symmetric algorithm which makes use of the same key for both encryption and decryption. There are also keyless algorithms which use no keys at all.
L. R. Knudsen, M. J. B. Robshaw, The Block Cipher Companion. Springer, 2011.
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