SUBCYPHER

Product Description

SubCypher is a little fun utility to learn about cryptanalyis. From the ReadMe file:

What does this program do?

It's a little fun application that can assist you in breaking very simple substitution cypher encryption on plain text. I wrote this in response to the December 2008 FBI Cryptanalysis challenge at http://www.fbi.gov/page2/dec08/code_122908.html.

How does it work?

First you paste the encrypted text into the field labelled "Cipher Text". In the case of the FBI challenge, this text was...:

VFWTDLCSWV. YD NSLMIJFWEJFD GSW SL NIJNQBLM FOBV EJFDVF DLNIGTFBSL. KBVBF YYY.AHB.MSK/NSCDC.OFZ FS EDF WV QLSY SA GSWI VWNNDVV.

The next step consists of "guessing" what certain passages in the encrypted text may mean and entering the decoded text for these passages into the program. In the above example, does the section "YYY.AHB.MSK/NSCDC.OFZ" ring a bell? This is surely a URL. We can't tell yet what the URL reads, but I would certainly guess that the domain part of this URL is "www.fbi.gov". Go figure. :)

SubCypher is available free of charge. You can download it here for Mac OS X and Windows.

Mac OS X Version

Version 1.0; Disk Image (.dmg), 4.6 MB

Requirements: Mac OS X 10.4 or later.

Windows Version

Version 1.0; ZIP file (.zip), 2.5 MB

Requirements: Windows XP Service Pack 2 or later. WinZip or a similar unpacking program might be required to unpack the downloaded file.