Cryptographic systems, and particularly stream ciphers, often use pseudorandom number generators to provide sequences of random numbers. The pseudorandom number generator often is initialized in an arbitrary state of a repeating sequence of states (i.e., a cycle) as some function of a keyword or key phrase. Thus, an arbitrary initialization of a pseudorandom sequence may result in a short cycle or pattern of different output values that could repeat during a long message or session. These repeated patterns make pseudorandom number generators vulnerable to automated attacks. To prevent patterns from occurring, longer sequences (large k values) can be used. However, for devices having small form factors (e.g., media players, mobile phones, etc.), power and memory constraints limit the length of the random number sequences that can be generated, resulting in an increased risk that detectable patterns will be generated.

Apple's patent presents us with a system; method and apparatus for providing random numbers of cryptographic strength that are suitable for use in cryptographic systems for small devices.

Apple's patent FIG. 2 shown below illustrates a block diagram of an entropy accumulator embodiment. Those interested in Apple's cryptography solution will read about Apple's Entropy Accumulator System, Chaos Generator Process Flows, a Signature Signing and Verification System and a Curve Parameter Structure.