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:

Program	User Interface	GPU Acceleration
rcrack	command line	-
rcrack_gui	GUI	-
rcrack_cl_amd	command line	AMD
rcrack_cl_amd_gui	GUI	AMD
rcrack_cuda	command line	NVIDIA
rcrack_cuda_gui	GUI	NVIDIA

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_cl_amd/rcrack_cuda Program

General Use

Assume rainbow tables are in directory c:\rt.

To crack single hash:

rcrack c:\rt -h fcea920f7412b5da7be0cf42b8c93759

rcrack_cl_amd c:\rt -h fcea920f7412b5da7be0cf42b8c93759

rcrack_cuda c:\rt -h fcea920f7412b5da7be0cf42b8c93759

To crack multiple hashes:

rcrack c:\rt -l hash_list_file

rcrack_cl_amd c:\rt -l hash_list_file

rcrack_cuda 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 c:\rt1 c:\rt2 -l hash_list_file

rcrack_cl_amd c:\rt1 c:\rt2 -l hash_list_file

rcrack_cuda c:\rt1 c:\rt2 -l hash_list_file

In the example above, the rcrack/rcrack_cl_amd/rcrack_cuda 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 c:\rt -lm pwdump_file

rcrack_cl_amd c:\rt -lm pwdump_file

rcrack_cuda c:\rt -lm pwdump_file

To load and crack NTLM hashes from pwdump file:

rcrack c:\rt -ntlm pwdump_file

rcrack_cl_amd c:\rt -ntlm pwdump_file

rcrack_cuda c:\rt -ntlm pwdump_file

Rainbow Table Lookup with rcrack_gui/rcrack_cl_amd_gui/rcrack_cuda_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 Group [group name]" to search rainbow tables in multiple directories sequentially. All rainbow table groups are defined in configuration file group.txt.

When rainbow tables are specified, hash cracking will start.

Performance Tips

Memory Requirement

4 GB memory is minimal and 8 GB or more memory 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

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