ES1020 core fully implements the ARC4 stream ciphering algorithm in hardware. For each input character, an output character is nerated. ES1020 ARC4 core allows simultaneous encryption/decryption of multiple independent sessions in a time-multiplexed fashion. Each ARC4 data ciphering session has associated a context. In ARC4, a ciphering context is fully defined by its encryption/decryption key and the internal state of the cipher (256 Bytes). Once the state of the cipher is initialized by the key, the key is no longer necessary for further operation. ARC4 core includes a direct interface to a context memory. This allows very fast context switching between different sessions. The interface to context memory is generic enough to match most common
types of compiled memory. ARC4 operation is identical for ciphering and deciphering so a single command cipher/decipher is provided for that purpose.