It occurs to me that specifying IVs for CBC mode in protocols like IPsec, TLS, etc. be generated by using a block cipher in counter mode and that the IVs be implicit rather than transmitted kills two birds with one stone.
The first bird is the obvious one: we now know IVs are unpredictable and will not repeat. The second bird is less obvious: we've just gotten rid of a covert channel for malicious hardware to leak information. Note that if you still transmit the IVs, a misimplemented client could still interoperate with a malicious counterparty that did not use the enforced method for IV calculation. If you don't transmit the IVs at all but calculate them, the system will not interoperate if the implicit IVs aren't calculated the same way by both sides, thus ensuring that the covert channel is closed. Perry -- Perry E. Metzger pe...@piermont.com _______________________________________________ The cryptography mailing list cryptography@metzdowd.com http://www.metzdowd.com/mailman/listinfo/cryptography
