This paper specializes the signature forgery by Coron, Naccache and Stern (1999) to Rabin-type systems. We present a variation in which the adversary may derive the private keys and thereby forge the signature on any chosen message. Further, we demonstrate that, contrary to the RSA, the use of larger (even) public exponents does not reduce the complexity of the forgery. Finally, we show that our technique is very general and applies to any Rabin-type system designed in a unique factorization domain, including the Williams’ M ³ scheme (1986), the cubic schemes of Loxton et al. (1992) and of Scheidler (1998), and the cyclotomic schemes (1995).