Paper 2003/162

Cryptanalysis of the Alleged SecurID Hash Function

Alex Biryukov and Joseph Lano and Bart Preneel

Abstract

The SecurID hash function is used for authenticating users to a corporate computer infrastructure. We analyse an alleged implementation of this hash function. The block cipher at the heart of the function can be broken in few milliseconds on a PC with 70 adaptively chosen plaintexts. The 64-bit secret key of 10$\%$ of the cards can be discovered given two months of token outputs and $2^{48}$ analysis steps. A larger fraction of cards can be covered given more observation time.

Note: New attack on the full Alleged SecurID Hash Function.