On Sep 22, 2011, at 13:01, Glenn Knickerbocker wrote: > On 09/22/2011 11:20 AM, Frank M. Ramaekers wrote: >> (something like ARC4)? > > That would be straightforward, given a way to reblock one stream with > the length of records on another. Just seed RANDOM with your key, and > COMBINE XOR to encode or decode. > In another context here recently here, John P. Hartmann hinted that RANDOM does not meet requirements of modern cryptographic strength. Of course, the key strength is no greater than the size of the seed. And the low-order bits of many PRNGs tend to repeat with a short period. (don't use modulo to restrict the range of such a PRNG.) This regularity could be exploited in cryptanalysis by observing statics of every fourth character in the ciphertext.
> So what's a simple way to reblock the output of RANDOM to match the > length of the input records? > I'd opt to PACK the input. It's solved a lot of blocking problems for us. -- gil
