Encrypting files

[funxus]

I've written a program that encrypts and decrypts files with a password, and it's especially written to work on USB flash memories. The zip file contains both a usable exe-file and the source code if anyone want to use it.

I wrote it to use it myself, and because I liked the challenge, but think I might as well post it here if anyone else is interested.

(I do realise the program doesn't have very much potential.)

 

[damunzy]

Sounds like a cool program to me. What type of encryption does it use?

 

[IceBlaZe]

Can you post the crypting algorithm in plain English? (I don't do much programming).

 

[Solver]

Bah, read the source. It's quite elgeant. The encryption is nothing uber-strong, but surely nice.

 

[Aphex_Twin]

I actually wrote such a program to smuggle some music out of an internet cafe (they had a filter and a copyright policy).

 

[funxus]

Thanks.

A part of the algorithm I found as an example in a book a long time ago, and I used it as a base to the algorithm, so I can't really take very much credit for it, although I altered a lot of it.

It turns a password into 3 numbers, using the ascii value of all the letters in the password. These numbers and a counter (first byte is 1, second byte is 2...) are then used to create a number that is subtracted from each byte, then to create a key number that is used to XOR the byte, and then the number subtracted in the beginning is added to the byte. This means that the same algorithm will both decrypt and encrypt the data. The password is stored as an encryption of itself, so decrypting the stored password returns the password itself.

I doubt it's uber-strong, but then again, I don't really plan to encrypt any government secrets with it.

 

[Solver]

One of the reasons it's not uber strong is exactly because it uses the ASCII-codes of encryption key characters. It's simply a practice that's very commonly adopted.