Tuesday, June 10, 2008

One-time Pad Tool

I just uploaded a new software tool on my website to perform one-time pad encryption. If you enter a plaintext and a one-time pad key, the little program converts the plaintext into numbers and calculates the ciphertext. The CT-46 table is used to convert the text into digits. The program contains a help section with instructions on how to use the pencil-and-paper version and the conversion table.

Although the program works exactly the same as the real method, it is meant for training purposes. As we all know, the only secure computer is a stand-alone laptop, stored in a safe. Given the many viruses, trojans and spyware it's useless to use a perfect crypto system on the most insecure device ever, your PC. The best way to apply one-time pads is simply with pencil and paper. However, the software is ideal to learn working with one-time pads, and if you do have a completely isolated PC and a good random number generator the program will save you lots of time and work.

All you want to know about one-time pads and the freeware program download at the one-time pad page on my website. More about working with one-time pads on this page.


[WinAmp] said...

Well, in some cases even a standalone laptop locked in a safe isn't really *the* safest ;)

David Richardson said...

I'm no cryptographer, but I have been giving some thought to secure encryption.

What about a ROT-n encrytion where n represents the position in the alphabet of the letter of the key. For example if my password is "secret" then the first letter would be replaced with its value +19, the second letter would be its value +5, the third letter +3, etc.

It would seem to me that in this way you would never be able to figure out which rotation is used without knowing the password. And the larger your password, the more secure it would be..

Dirk Rijmenants said...

Hi David,

what you suggest is called a poly-alphabetic cipher. These are totally insecure and easily broken by a frequency count of all 1st, 2nd, 3th... letters seperately. All these types of encryption are variants of the Vigenere cipher, and all are insecure.

A poly-alpha cipher could be totally secure if you would select a random key letters for each individual message letter, but then, that's what we call a one-time pad.