Some MORON wrote an article in Computer Shopper, about doing a one-time pad with a PRBS... in fact, he even challenged any cryptographers to break it. (He used a 32-bit seed for the PRBS.) He also included a number of fallacies in the article, among them that you change your algorithm when you think the enemy knows what it is, but you change your keys regularly even when you don't have any basis to think so. How *do* you break this cypher? He is generating a lot of random numbers between 0 and 255, and xor'ing each successive one with the next byte of plain- text. I know that this is a trivial cypher to break, according to PRZ at least, but how do you do it? This arrogant moron with pretensions to cryptographic knowledge needs to be corrected. (Some might say the above epithet applies to me too, to which I reply: I don't pretend to know crypto. I just read cypherpunks.) He is: David Stafford, care of Computer Shopper ONe Park Avenue New York, NY 10016 This kind of misinformation is dangerous to the public at large. The article is on page 558 af the July, 1993 Computer Shopper. It uses a random number generator, (now that I look, it's not a PRBS) from the June, 1993, Computer Shopper, by the same author. The random number generator used is like this: It uses a global variable called RandomSeed, and each time thru the random function, RandomSeed, a 32-bit long, is multiplied by 0x015a4e35, and incremented; and then the new Randomseed, modulo the largest desired return value, is returned. (Actually, mod the largest desired value +1.) a code fragment: #define MULTIPLIER 0x015a4e35L #define INCREMENT 1 long RandomSeed; int GetRandomNumber(int Range) { RandomSeed = MULTIPLIER * RandomSeed + INCREMENT; return(RandomSeed % Range); } So how do you crack this cipher without trying all the keys, guys? Kragen