This question already has an answer here:

Encrypting the file using same encryption algorithm using different Keys can increase the security or not?

marked as duplicate by random65537, GdD, rook, Ayrx, Lucas Kauffman Mar 14 '13 at 16:50

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

  • @makerofthings7 Strictly speaking, this is not the same question. The proposed duplicate asks about doubling up with different algorithms. This asks about doubling up with the same algorithm, but different keys. In the end, the answer is the same but the questions aren't quite. – Iszi Mar 14 '13 at 16:39
  • @Iszi You're right, and given extra thought about this, I think that using different keys would more security if those keys are given to two different people (etc). Security depends on key management. But the real answer should be "if your computer will be performing X amount of computational power, and using two keys = 2x, and you don't need two keys, you're better off making the key length longer". Pornin has something similar here but I can't find it. – random65537 Mar 14 '13 at 17:15
  • @makerofthings7 We're discussing this rather extensively in chat. Come join us! The short of it (so far) is that double encryption doesn't provide as much value as encrypting once with a double-length key would - so why not just do that? However, it does have its uses in split knowledge / dual control scenarios such as for a Captain and XO on a sub with nuclear missiles. – Iszi Mar 14 '13 at 17:28
  • For those interested, here is the link to the chat archive Lots of useful or interesting information there – random65537 Mar 14 '13 at 18:10