>extrapolating to 50kB gives me 0.3625 seconds It should give you much more than that, considering that the green (SHA256) graph hits almost 0.1s at just 1000

>extrapolating to 50kB gives me 0.3625 seconds It should give you much more than that, considering that the green (SHA256) graph hits almost 0.1s at just 1000 bytes of input. >either crypt() is doing much more than I tought (is salting _that_ expensive?) glibc crypt() is probably doing more than you thought, but it's not salting: in SHA256 mode, various combinations of the key and intermediate hash digests are repeatedly hashed in a certain pattern for 5000 times, although the number of rounds can be changed just like the hashing algorithm. (This is a glibc implementation detail; not all crypt() implementations support extensions like SHA256 mode.) In general, all general purpose cryptographic hash functions are reasonably fast.