Time-Memory Trade-Off Attack on FPGA Platforms: UNIX Password Cracking

This paper presents a hardware architecture for UNIX password cracking using Hellman’s time-memory trade-off; it is the first hardware design for a key search machine based on the rainbow variant proposed by Oechslin. The implementation target is the Berkeley BEE2 FPGA platform which can run at 400 million password calculations/second. Our design targets passwords of length 48 bits (out of 56). This means that with one BEE2 module the precomputation for one salt takes about 8 days, resulting in a storage of 56 Gigabyte. For the precomputation of all salts in one year we would need 92 BEE2 modules. Recovering an individual password requires a few minutes on a Virtex-4 FPGA.