I want understand prx decryption...

[peb]

Hi!

So, all is in title... I read psardump src to understand how the decryption can work, but like it support all firmware, it's not very easy to understand I think...

So if you could give me way (even small), I could search more information after...

thx ;)

[jean]

Well... think of it this way: in PSP there is a black-box that you feed with an encrypted code and get back an unencrypted one. PSP needs unencrypted code to run it. So we give code to the black-box and get back executable one without any idea of what the blackbox does...Well, actually we have SOME idea, but you understood. Every asymmetric cryptography system on earth works quite the same way, so go for wikipedia if you have to start somewhere.

[peb]

Lot of thinks to took time to help me.

So I had search and read informations about asymmetric cryptography system, footprint, hash function,MD5, SHA-1...
1- You speak about black-box, but it's an obligation to know encryption to decrypt prx...So for the prx we know if it's MD5, SHA-1,...?
2- When we want find the private key, we use brute force?
3- How use the private key to decrypt prx?

[Raphael]

1- You speak about black-box, but it's an obligation to know encryption to decrypt prx...

No. You can decrypt without knowing encryption. Read again the "asymmetric" part of asymmetric encryption. Apart from that, the PSP has a decryption hardware that we use to do the work for us, without having to know how it really works. We just need to know how to talk to that hardware.

2- When we want find the private key, we use brute force?

No. We don't want to find it and we surely don't use brute force, unless we had a couple of life times to spend waiting.

3- How use the private key to decrypt prx?

If we had it and knew the exact algorith of encryption, we could decrypt it with our own functions. But we don't and most likely never will.

[jojojoris]

2- When we want find the private key, we use brute force?

No. We don't want to find it and we surely don't use brute force, unless we had a couple of life times to spend waiting.

Well. I've one question about this.

I know its too hard to do it on 1 pc. But what about 1000 pc's? I know there are some projects in the world who uses unused CPU from a big number of pc from people like you and me to help with enormouse calcualtions. Is this not something we can use for brutoforce cracking the key.

I hope you understand what i mean. I'm not the best in english.

[moonlight]

You can't bruteforce something you don't even know the algorithm.
It is probably AES128, at least now it is a total FACT that kirk uses AES 128 algorithm (not confirmed it is used for prx's though), but mixed with lot of shits, various loops, "private" keys in hardware, etc

[jean]

I know its too hard to do it on 1 pc. But what about 1000 pc's?

My first degree thesis was somehow about parallelization, too. I can swear there're problems you cannot cut into chunks like grid computing use to do. Asymmetric cryptography is a smart tought.