Cipher

In cryptography, a cipher is an algorithm that can encrypt plaintext to make it unreadable, and to decrypt the encoded data back to plaintext again.

Ciphers were common long before the information age (e.g., substitution ciphers, transposition ciphers, and permutation ciphers), but none of them were cryptographically secure except for the one-time pad.

In the modern age, ciphers have evolved dramatically. AES, RSA>) and Blowfish>) are examples of ciphers that are integral part of contemporary encryption standards and systems.

Modern ciphers are designed to withstand attacks discovered through cryptanalysis. There is no guarantee that all attack methods have been discovered, so each algorithm is recommended for different purposes based on known classes of attacks.