Do any Bitcoin exchanges allow you to use private keys to credit account?
the advantage being it would be hard to hack, as you enter the keys the bitcoin would be accessible to the exchange and they could immediately send it on to a new address secure (for a small fee)
Even if a keylogger was on your computer it would be hard compete.
I suppose a keylogger could send all keys for the last digit place, and get ahead a bit....
what do you think?
(this also ignores the risks of exchanges themselves but that's a different story)
I dont think it would do you any good if your system is already compromised. The only defense you can hope with this scheme is that the malware that infected your system does not scan for private keys. If it would be common the private key you send the exchange could easily be modified locally without your knowledge.
Other than that I think its best to handle private keys in an unencrypted form as little as possible. You essentially suggest that a user puts their private key in the clipboard befor sending it to the server, because we all know no one would type the key by hand. This can easly lead to the private key being compromised, e.g. because the user later pastes the key in a chat.