Editing ISAAC (cipher) (section)

== Operation ==

The ISAAC [[algorithm]] has similarities with [[RC4]]. It uses an [[Array data structure|array]] of 256 four-octet [[Integer (computer science)|integers]] as the internal state, writing the results to another 256 four-octet integer array, from which they are read one at a time until empty, at which point they are recomputed. The computation consists of altering ''i''-element with (''i''⊕128)-element, two elements of the state array found by indirection, an accumulator, and a counter, for all values of ''i'' from 0 to 255. Since it only takes about 19 32-bit operations for each 32-bit output word, it is very fast on 32-bit computers.