Saturday, July 23, 2011

JTR (Password Cracking) – John the Ripper 1.7

The new “features” this time are primarily performance improvements possible due to the use of better algorithms (bringing more inherent parallelism of trying multiple candidate passwords down to processor instruction level), better optimized code, and new hardware capabilities (such as AltiVec available on PowerPC G4 and G5 processors).

In particular, John the Ripper 1.7 is a lot faster at Windows LM hashes than version 1.6 used to be. (Since JtR is primarily a Unix password cracker, optimizing the Windows LM hash support was not a priority and hence it was not done in time for the 1.6 release.) John’s “raw” performance at LM hashes is now similar to or slightly better than that of commercial Windows password crackers such as LC5 – and that’s despite John trying candidate passwords in a more sophisticated order based on statistical information (resulting in typical passwords getting cracked earlier).


John the Ripper 1.7 also improves on the use of MMX on x86 and starts to use AltiVec on PowerPC processors when cracking DES-based hashes (that is, both Unix crypt(3) and Windows LM hashes). To my knowledge, John 1.7 (or rather, one of the development snapshots leading to this release) is the first program to cross the 1 million Unix crypts per second (c/s) boundary on a general-purpose CPU. Currently, John 1.7 achieves up to 1.6M c/s raw performance (that is, with no matching salts) on a PowerPC G5 at 2.7 GHz (or 1.1M c/s on a 1.8 GHz) and touches 1M c/s on the fastest AMD CPUs currently available. Intel P4s reach up to 800k c/s. (A non-public development version making use of SSE also reaches 1M c/s on an Intel P4 at 3.4 and 3.6 GHz. I intend to include that code into a post-1.7 version.)

Additionally, John 1.7 makes an attempt at generic vectorization support for bitslice DES (would anyone try to set DES_BS_VECTOR high and compile this on a real vector computer, with compiler vectorizations enabled?), will do two MD5 hashes at a time on RISC architectures (with mixed instructions, allowing more instructions to be issued each cycle), and includes some Blowfish x86 assembly code optimizations for older x86 processors (the Pentium Pro family, up to and including Pentium 3) with no impact on newer ones due to runtime CPU type detection.

Speaking of the actual features, John 1.7 adds an event logging framework (John will now log how it proceeds through stages of each of its cracking modes – word mangling rules being tried, etc.), better idle priority emulation with POSIX scheduling calls (once enabled, this almost eliminates any impact John has on performance of other applications on the system), system-wide installation support for use by *BSD ports and Linux distributions, and support for AIX, DU/Tru64 C2, and HP-UX tcb files in the “unshadow” utility.

Finally, there are plenty of added pre-configured make targets with optimal settings, including ones for popular platforms such as Linux/x86-64, Linux/PowerPC (including ppc64 and AltiVec), Mac OS X (PowerPC and x86), Solaris/sparc64, OpenBSD on almost anything 32-bit and 64-bit, and more.
Of course, all platforms supported by John 1.6 (including plain x86 running most Unix-like systems, Win32, or DOS) are still supported. Similarly, pre-compiled binary distributions of John 1.7 for Win32 and DOS are made available.
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