Improved Fast Correlation Attack Using Low Rate Codes

In this paper we present a new and improved correlation attack based on maximum likelihood (ML) decoding. Previously the code rate used for decoding has typically been around r=1/214. Our algorithm has low computational complexity and is able to use code rates around r=1/233. This way we get much more information about the key bits. Furthermore, the run time for a successful attack is reduced significantly and we need fewer key stream bits.

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