RC4 generates a pseudorandom stream of bits (a keystream) which, for encryption, is combined with the plaintext using bit-wise exclusive-or; decryption is performed the same way (since exclusive-or is a symmetric operation). (This is similar to the Vernam cipher except that pseudorandom bits, rather than random bits, are used.) To generate the keystream, the cipher makes use of a secret internal state which consists of two parts:

1. A permutation of all 256 possible bytes
2. Two 8-bit index-pointers.

The permutation is initialized with a variable length key, typically between 40 and 256 bits, using the key-scheduling algorithm (KSA). Once this has been completed, the stream of bits is generated using the pseudo-random generation algorithm (PRGA).

This encoder will let you specify the key and the text to encrypt or decrypt. The encrypted text is represented in hexadecimal format, the decrypted text is in clear.

Encrypt Decrypt

The key:

This is your encoded or decoded text: