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KISS: A Bit Too Simple

KISS (`Keep it Simple Stupid') is an efficient pseudo-random number generator specified by G. Marsaglia and A. Zaman in 1993. G. Marsaglia in 1998 posted a C version to various USENET newsgroups, including \texttt{sci.crypt}. Marsaglia himself has never claimed cryptographic security for the KISS generator, but many others have made the intellectual leap and claimed that it is of cryptographic quality. In this paper we show a number of reasons why the generator does not meet the KISS authors' claims, why it is not suitable for use as a stream cipher, and that it is not cryptographically secure. Our best attack requires about 70 words of generated output and a few hours of computation to recover the initial state.


Greg Rose is a Senior VP in the office of the Chief Scientist for QUALCOMM Incorporated, where he works on cryptographic security and authentication for third-generation mobile phones and other technologies and manages other diverse groups. He holds a number of patents for cryptographic methods and has successfully cryptanalyzed widely deployed ciphers. Greg was program chair of the 1996 and 2000 USENIX Security Symposia, and General Chair of Crypto 2003. Some of his papers and free software are available at

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