Hey all

I'm writing a little Password Diary application in C at the moment but am not sure of the best encryption function to use.

Does anyone know of any really good ones?

You should [b]NOT[b] use any encryption scheme, that is just made by a programmer. Try to check www.gnupg.com you should find, c programming encryption libraries there. If you can't get them to compile, check that you have install all it requires.

Encryption is one of those areas where folks who haven't had a lot of experience and coursework give some REALLY bad answers.

First off - there is no such thing as an absolutely uncrackable encryption algorithm with the exception of the OTP algorithm - which is completely impractical to use for encryption. So I'm sure somebody will tell you that such and such encryption can be cracked. And it can - if you let a Cray computer work on it for the next 100 years.

The standard algorithm for what you want is called one-way encryption. Message digest 5 - MD5 is a good one. It is a one-way hash. No matter how long the input string is, the algorithm returns 16 bytes (usually printed in hex). There are other algorithms.

See man md5

Looked at MD5 but for a Password Diary it isn't appropriate for what I need...

What I need is to be able to add the password to the hidden encrypted file, then when it is needed, be able to view the password (by decrypting it obviously)...

I also looked at crypt but I'm unsure of how to decrypt it...

Two-way encryption (you can decode the encypted message) is what you need. Normally, password files are not meant to be decrypted. linux uses crypt() to hash passwords one-way.

Most of these algorithms requires the use of an extended precision integer library (GNU MP) the algorithms are: RAS, PGP, etc. The math isn't bad, just uses monster numbers.

Here is a pretty good explanation:

http://world.std.com/~franl/crypto/rsa-guts.html

I know password files aren't meant to be decrypted but this is a diary - without encryption it would be a case of would you want everyone being able to see your list of passwords?

All I need to do is encrypt/decrypt the FILE as authentication is met. Unfortunately I feel an experienced programmer could crack this... I have heard that Blowfish would do the job but i'm not sure.

I looked the site you directed me to but I got a bit confused, will try to figure it out when I have some time.

Tea, blowfish, twofish will work.

Thanks jim - i'll check these out today