SWIFFT: a Modest Proposal for FFT Hashing


Lyubashevsky, V., Micciancio, D., Peikert, C., Rosen, A. (2008). SWIFFT: A Modest Proposal for FFT Hashing. In: Nyberg, K. (eds) Fast Software Encryption. FSE 2008. Lecture Notes in Computer Science, vol 5086. Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-540-71039-4_4


We propose SWIFFT, a collection of compression functions that are highly parallelizable and admit very efficient implementations on modern microprocessors. The main technique underlying our functions is a novel use of the Fast Fourier Transform (FFT) to achieve “diffusion,” together with a linear combination to achieve compression and “confusion.” We provide a detailed security analysis of concrete instantiations, and give a high-performance software implementation that exploits the inherent parallelism of the FFT algorithm. The throughput of our implementation is competitive with that of SHA-256, with additional parallelism yet to be exploited.

Our functions are set apart from prior proposals (having comparable efficiency) by a supporting asymptotic security proof: it can be formally proved that finding a collision in a randomly-chosen function from the family (with noticeable probability) is at least as hard as finding short vectors in cyclic/ideal lattices in the worst case.

Keywords: Fast Fourier Transform, Hash Function, Random Oracle, Ideal Lattice, Compression Function

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