RC4 (Rivest Cipher 4) is a symmetric cryptography algorithm and is one of the most used encryption algorithms in the world because of its simplicity and speed. it is used in popular protocols such as SSL and WEP. Although, RC4 falls short of the high standards of security, some systems based on RC4 are secure enough for practical use. RC4 is a Vernam cipher, which means that it generates a keystream that, for encryption, is combined with the plaintext using XOR. As with any Vernam cipher decryption is performed the same way.

In this implementation the plain text and key are entered as base 95 ASCII (keyboard accessible characters) strings. Ciphertext cannot be represented in ASCII because of non-rendering of ASCII codes 0-31 and 127-160.