1.7 times as long as basic RC4. All arithmetic modulo 256. << and >> are left and right shift, ⊕ is exclusive OR while GeneratingOutput: i := i + 1 a := S[i] j := j + a Swap S[i] and S[j] (b := S[j]; S[j] := S[i]; S[i] := b;) c := S[i<<5 ⊕ j>>3] + S[j<<5 ⊕ i>>3] output (S[a+b] + S[c⊕0xAA]) ⊕ S[j+b] endwhile This algorithm has not been analyzed significantly. Spritz In 2014, Ronald Rivest gave a talk and co-wrote a paper on an updated redesign called Spritz. A hardware accelerator of Spritz was published in Secrypt, 2016 and shows that due to multiple nested calls required to produce output bytes, Spritz performs rather slowly compared to other hash functions such as SHA-3 and the best known hardware implementation of RC4. The algorithm is: All arithmetic is performed modulo 256 while GeneratingOutput: i := i + w j := k + S[j + S[i]] k := k + i + S[j] swap values of S[i] and S[j] output z := S[j + S[i + S[z + k]]] endwhile The value , is relatively prime to the size of the S array. So after 256 iterations of this inner loop, the value (incremented by every iteration) has taken on all possible values 0...255, and every byte in the S array has been swapped at least once. Like other sponge functions, Spritz can be used to build a cryptographic hash function, a deterministic random bit generator (DRBG), an encryption algorithm that supports authenticated encryption with associated data (AEAD), etc. In 2016, Banik and Isobe proposed an attack that can distinguish Spritz from random noise. RC4-based protocols WEP TKIP (default algorithm for WPA, but can be configured to use AES-CCMP instead of RC4) BitTorrent protocol encryption Microsoft Office XP (insecure implementation since nonce remains unchanged when documents get modified) Microsoft Point-to-Point Encryption Transport Layer Security / Secure Sockets Layer (was optional and then the use of RC4 was prohibited in RFC 7465) Secure Shell (optionally) Remote Desktop Protocol (optionally) Kerberos (optionally) SASL Mechanism Digest-MD5 (optionally, historic, obsoleted in RFC 6331) Gpcode.AK, an early June 2008 computer virus for Microsoft Windows, which takes documents hostage for ransom by obscuring them with RC4 and RSA-1024 encryption PDF Skype (in modified form) Where a protocol is marked with "(optionally)", RC4 is one of multiple ciphers the system can be configured to use.