I've noticed quite a few cryptographic algorithms speak mainly of the time complexity of an algorithm. For example, with a hashing function h, find x given y = h(x). We normally speak on how long it will take. Or the time to find the discrete log for a public key.
Edit:
While writing this question, I pondered that maybe because for most algorithms in cryptography (that I have seen) , have O(1) space time complexity. i.e. If the solution does not work, we throw it away and encrypt.
Clarification on this will be really helpful.