[p4bl0]

This question only makes sense if you give the threat-model to consider.

Is it only classical cryptanalysis on the cryptographic algorithm? Or do you take into account the programming mistakes (not necessarily related to crypto) of specific implementations? Or do you allow side-channel or fault-injection attacks, which will be able to break most algorithms, if they are not implemented with specific countermeasures?

In anyway, it is a very difficult question which doesn't have a single definite answer.

[logicalmind]

Exactly. A lot is lost when security deals strictly with theory instead of pragmatism. Theoretical breaks in crypto algorithms are important, but much weaker links in the chain are easier to attack. Using the best, unbreakable crypto does not protect you from more realistic attacks.

Obligatory XKCD:

http://xkcd.com/538/