The unique key

[igor.alexandrov]

Hello all Sorry for my English, i am from Russia )
I have got a problem. I need a crossplaform method to generate some unique per machine key. I will use it in my RC4 crypt algorithm as a crypt key.
In Windows, I know, there is something like WinId, but what to do in Linux and Mac?
Thanks

[marcel]

WinId is the platform window handle id, and it most certainly will not be unique between sessions.

For your need QUuid is more suitable.

[igor.alexandrov]

I know about QUuid, but i also keno that it is not cryptographic-quality random number generator.

[marcel]

I know about QUuid, but i also keno that it is not cryptographic-quality random number generator.

And how is WinId better than a GUID?

If you want to use "cryptographic-quality random number generator" then take a look at libgcrypt at http://www.gnupg.org/

[igor.alexandrov]

No, no, I really don't think that WinId is better then QUuid. It was just an example About GnuPG, thanks, I forget about it.

[wysota]

Just generate a large random number and test it for being prime. You don't need Qt for that.

[Thomas]

I know it is a bit late, but...

If it is just about a random number, Linux has a two very nice devices which provide you with entropy based rand numbers. Check the man page (man urandom). If it is about random uuids, read the (publicly readable) file /proc/sys/kernel/random/uuid. This file creates on every read access a new random uuid.

Cheers,
Thomas

[wysota]

I just read the original question again. You are using RC4, so your large number doesn't even have to be prime. If you want a custom random number generator, you can find some in "Numerical Recipes in C".

[Thomas]

I just read the original question again. You are using RC4, so your large number doesn't even have to be prime. If you want a custom random number generator, you can find some in "Numerical Recipes in C".

But the code in Numerical Recipies is not free, so it limits the usage pretty much. For instance the project I am working for cannot use those code snippets because our software is GPL.

[wysota]

Who said you should take the code? The algorithm is what is important, the code can be written from scratch. Once you get a grip of how random number generators work (that they are shift registers with feedback), you can design (and implement) your own.