Looks like there is some renewed interest in Rabin-Williams signatures out there.
Sharing my old implementation in case this helps the community. There is no audit, use at your own risk:
github.com/mmagician/Rabin-W…
Rabin-Williams has a much faster verifier than RSA, because it involves squaring instead of exponentiation (or, put simply, exponent e=2).
Its security relies on the difficulty of finding quadratic residues mod n (composite), which follows from the difficulty of factoring n.