Fault Cryptanalysis for Breaking A5/1

          Marcin Gomulkiewicz, Miroslaw Kutylowski, Pawel Wlaz


The paper demonstrates a fault attack on A5/1 stream cipher. It is  done
by imposing intentional error bits on chosen registers. The attack works
very efficiently and demonstrates weakness of this kind of cipher in yet
another  way. The attack needs only a small amount of generated bits and
(what differs the attack from other known  fault  cryptanalysis  attacks
and  makes  it  more  realistic)  does not need the correct sequence for
comparison.

The results show that applications  using  hardware  implementations  of
A5/1 for other purposes than securing GSM traffic must be aware of quite
efficient potential fault attack.

(research cunducted in cooperation with BTU Cottbus)