Download v1.1 (for Windows 95 / 98 / ME / NT 4.0 / 2000 / XP / 2003 / Vista)


CryptF is a file encryption tool that can encrypt with either 3-DES or IDEA.

Usage instructions

Download the exe file and run it. How to use it should be pretty self explainatory.


Please read the Q&A before you use the program so you don't misunderstand anything important!


Q: Which encryption algorithms does CryptF support?

A: It supports 3-DES and IDEA, and the key is derived from the passphrase using MD5. The file is encrypted using the selected algorithm in CBC (Cipher Block Chaining) mode. The initialization vector is created by the ordinary rand C function, as is the padding for the last block if there isn't enough file data to fill a complete block. There is no check for weak keys either for 3-DES or IDEA. There is no extra integrity checking in this version.

Q: Which key sizes are used?

A: 3-DES uses 112 effective key bits and IDEA uses 128 bits.

Q: Where do the algorithm implementations come from?

A: I have implemented the algorithms (3-DES, IDEA and MD5) from scratch using descriptions of the algorithms (not looking at any source code). I have tested them against all the test vectors I could find. Of course implementing them all from scratch could mean creating a bunch of new bugs that are not present in older implementations, as well as getting slower code, but I want to write all code in my tools myself. If you want a more reliable implementation, please download another program and use it instead.

Q: Can you guarantee that my data will be safe if I encrypt it with CryptF?

A: No. You should never trust an encryption algorithm completely. And especially you should never trust the implementation of it, nor any other code for that matter.

Q: Are there any backdoors in the program?

A: No. At least there are no backdoors that I have put there on purpose. But there may be unintentional bugs that weaken the encryption and so on. And no, I haven't let the NSA, CIA, FSB, FAPSI, or even the SCIS (Santa Clause Intelligence Service - the guys who make sure that you have been nice all year before you get any stuff on Christmas) make any weird modifications to the code.

Q: Where do I find the output from the program?

A: If you encrypt "file.dat" the result will be in "file.dat.enc" and the original file will not be deleted. If you decrypt "file.dat.enc" the result will be in "file.dat" and the encrypted file will not be deleted.

Q: I have a question that is not covered here. Where can I get help?

A: Send me your question. I can't promise that I will have time to answer, but I'll do my best.

© Arne Vidstrom. All rights reserved.