This is what I wish to defend the data against. Basically someone taking it for the computer itself, not nessesarally the data. Basically frustrate them from gaining access to anything critical and let them delete or reformat it so they can have a clean system.
Had to respond to this. I have some stuff encrypted on a DVD. The decryption path is USB token, smartcard, passphrase,smartcard,USB token,passphrase. (These are all symmetric keys,created for the purpose of securing this date. Every key is unique)) This is a reallife case, albeit extreme). Do you think the men in black can get at my data ?
Given sufficient time and resources: yes.
From a mathematical standpoint, it’s not a clear-cut case that repeatedly-applied encryption is necessarily more secure than a single layer. Consider dual-applied ROT-13 for a very simple example. I’ll let someone who has more recent knowledge of encryption systems take up that issue.
But the other thing working against you is raw computing power. Governments have access to a lot of it, and the power of even small desktop computers is still growing rapidly year after year. Does your data need to stay secure “forever”? Not a chance – brute force methods will probably be able to crack it in the next fifty years. Does it just need to stay secure for the next 5-10 years? Then it depends on what level of interest the “men in black” take. If they think there are (say) plans for a terrorist attack in that data, they WILL decrypt it.
Also, remember that in many cases a judge can compel you to give up the keys, which makes it an issue of whether the data’s worth more to you than the consequences of refusing the order.