[upofadown]

Si (2^32)*8 works out to 34GB for TDES. How many applications involve encrypting that much data in one go?

[fc417fc802]

Sorry, calling that a block limit was an error by omission on my part. 2^32 yields a 50% chance of reuse. If we pick a sane security margin it's a lot smaller. Assuming I did the math correctly just now, 2^-32 only gives you ~2^17 blocks; dropping that to 2^-24 yields ~2^21 blocks.

[upofadown]

Off the top of my head, NIST was suggesting something like 8GB as the working limit. It would depend on your risk tolerance and the application in practice I guess. For something like video you might not really care about exposing a few 8 byte blocks here and there where the exposure is one block XORed with the other.