Finding Preimages of Multiple Passwords Secured with VSH

In this paper we present an improvement to the preimage attacks on very smooth hash (VSH) function. VSH was proposed as a collision resistant hash function by Contini et al., but it has been found lacking in preimage resistance by Saarinen. With our method, we show how to find preimages of multiple passwords secured by VSH. We also demonstrate that our method is faster in finding preimages of multiple passwords than the methods proposed earlier. We tested the methods with five, ten and fifty randomised alphanumeric passwords. The results show that our method is many times faster than the original method of Saarinen and almost three times faster than the improved method proposed by Halunen et al. Furthermore, we argue that the methods presented previously and our method are essentially the only significantly different methods derivable from Saarinen´s work.