问题
My X system uses public key to decrypt a cipher and do some work based on that. But user of the system whom i do not trust has access to the system, cipher and the key.
So what he can do is change the cipher, create another set of keys encrypt using private key and replace the cipher and public key both. So next time system will not know that message has change. I basically do not care if user can read it, my problem is he can not change it, so i thought of a MAC unfortunately that evil user can change the MAC as he has the access to the repository.
Big problem is that user going to always have unlimited access to cipher and the key(s) now how i can secure the whole thing?
回答1:
Your problem appears to be one of key management. How do client programs obtain the server public key? Do they ask the server directly? Or do they get the server public key from some other independent source? Wouldn't the client become suspicious if the public key changed one day without notice?
来源：https://stackoverflow.com/questions/8950732/security-from-evil-user