wharf uses two hashing algorithms:
- The weak hashing algorithm used in the original RSync paper
- MD5 as the "strong" hashing algorithm
MD5 isn't cryptographically strong in any way, but that's besides the point. It is a fast hash, of which many optimized implementations exist, and that allows detecting differences between files efficiently.
If the block size were to be increased, swapping MD5 out for a longer and stronger hash would be advantageous (with the caveats indicated in the Block size appendix).