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0 pointsfc417fc8021mo ago0 comments

I'm not a cryptographer but to me "broken" seems to imply that the core algorithm itself can be attacked. If merely applying it in certain ways as part of some larger system can fail then aren't most (possibly all) ciphers broken? It's entirely possible to do all sorts of stupid things.

Granted, a 2^32 block limit is pretty severe by modern standards.

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upofadown1mo ago

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

fc417fc802OP1mo ago

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.

upofadown1mo ago

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.

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0 pointsfc417fc8021mo ago0 comments

Granted, a 2^32 block limit is pretty severe by modern standards.

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upofadown1mo ago

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

fc417fc802OP1mo ago

upofadown1mo ago

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