Hash Cracking with Rainbow Tables

Introduction

This document explains the rcrack program. The rcrack program lookup existing rainbow tables for the plaintext of user supplied hash.

Six similar programs are available:

ProgramUser InterfaceGPU Acceleration
rcrackCommand Line
rcrack_cudaCommand LineNVIDIA CUDA
rcrack_clCommand LineAMD OpenCL
rcrack_guiGUI
rcrack_cuda_guiGUINVIDIA CUDA
rcrack_cl_guiGUIAMD OpenCL

Command line program is ideal for batch processing, and GUI program is easy to use.

Rainbow tables used by rcrack program must already be sorted with rtsort program, and optionally converted to .rtc file format with rt2rtc program.

Rainbow Table Lookup with rcrack/rcrack_cuda/rcrack_cl Program

General Use

Assume rainbow tables are in directory c:\rt.

To crack single hash:

rcrack/rcrack_cuda/rcrack_cl c:\rt\*.* -h fcea920f7412b5da7be0cf42b8c93759

To crack multiple hashes:

rcrack/rcrack_cuda/rcrack_cl c:\rt\*.* -l hash_list_file

In the example above, hash_list_file is a text file with each hash in one line.

To lookup rainbow tables in multiple directories:

rcrack/rcrack_cuda/rcrack_cl c:\rt1\*.* c:\rt2\*.* -l hash_list_file

In the example above, the rcrack/rcrack_cuda/rcrack_cl program will lookup rainbow tables in c:\rt1 and c:\rt2 directories sequentially.

Special Consideration for LM/NTLM Hash

LM/NTLM hashes are usually saved in text file of pwdump format.

Content of typical pwdump file:

Administrator:500:1c3a2b6d939a1021aad3b435b51404ee:e24106942bf38bcf57a6a4b29016eff6::: Guest:501:a296c9e4267e9ba9aad3b435b51404ee:9d978dda95e5185bbeda9b3ae00f84b4:::

To load and crack LM hashes from pwdump file:

rcrack/rcrack_cuda/rcrack_cl c:\rt\*.* -f pwdump_file

To load and crack NTLM hashes from pwdump file:

rcrack/rcrack_cuda/rcrack_cl c:\rt\*.* -n pwdump_file

Rainbow Table Lookup with rcrack_gui/rcrack_cuda_gui/rcrack_cl_gui Program

Step 1: Load the Hashes

Step 2: Specify the Rainbow Tables to be Searched

Select "Search Rainbow Tables..." to search individual rainbow tables.

Select "Search Rainbow Tables in Directory..." to search all rainbow tables in a directory.

Select "Search Rainbow Tables in Profile..." to search rainbow tables in multiple directories.

When rainbow tables are specified, hash cracking will start.

Performance Tips

32-bit Operating System vs. 64-bit Operating System

64-bit operating system is recommended so more than 2 GB memory can be used by application.

Memory Requirement

4 GB memory with 64-bit operating system is recommended. Larger memory always help to improve performance when searching large rainbow tables.

Hard Disk

Because rainbow table must be loaded from hard disk to memory to look up and some rainbow table set can be as large as hundreds of GB, hard disk performance becomes a very important factor to achieve overall good hash cracking performance.

We suggest put rainbow tables in RAID 0 volume with multiple hard disks. Windows operating system natively support software RAID 0 called "striped volume".

The rcrack program always read data from hard disk sequentially. There is no random access.

Multiple GPUs

RainbowCrack software supports GPU acceleration with CUDA enabled GPUs from NVIDIA and OpenCL enabled GPUs from AMD.

GPU acceleration with multiple GPUs is supported. To get optimal performance, all GPUs need be of same model.

If exact model of the GPUs is different, rcrack_cuda[_gui]/rcrack_cl[_gui] program try to balance the computing load based on core number of each GPU.

The SuperFetch Feature of Windows

SuperFetch is a feature of Windows Vista & Window 7 that allocate many memory to preload those frequently used applications from hard disk, so further launch of these applications will be faster.

The SuperFetch feature consumes many memory and hard disk bandwidth; both are critical resources for fast rainbow table lookup.

We suggest disable the SuperFetch service (Computer Management -> Services and Applications -> Services -> Superfetch) when rcrack program is running.

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