>> Why do you need a cryptographically strong generator for IVs?
> CBC's IV's need to be unpredictable to avoid the recently discovered
> CBC "oracle" attack.  [...explanation...]

Well, it's a relatively weak attack; it's chosen-plaintext, if nothing
else.  Nonetheless, it's interesting.

It also isn't defeated by using unpredictable IVs.  The only way a
predictable IV makes any of it any easier is that a tiny piece of the
computation can be done in advance, by predicting the IV - but it's an
utterly trivial piece, just one XOR.

...or am I missing something?

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