An OAEP Variant With a Tight Security Proof
We introduce the OAEP++ encoding method, which is an adaptation of the OAEP encoding method, replacing the last step of the encoding operation with an application of a block cipher such as AES. We demonstrate that if $f$ is a one-way trapdoor function that is hard to invert, then OAEP++ combined with $f$ is secure against an IND-CCA2 adversary in the random oracle model. Moreover, the security reduction is tight; an adversary against $f$-OAEP++ can be extended to an $f$-inverter with a running time linear in the number of oracle queries.
Security Proofs for the RSA-PSS Signature Scheme and Its Variants
We analyze the security of different versions of the adapted RSA-PSS signature scheme, including schemes with variable salt lengths and message recovery. We also examine a variant with Rabin-Williams (RW) as the underlying verification primitive. Our conclusion is that the security of RSA-PSS and RW-PSS in the random oracle model can be tightly related to the hardness of inverting the underlying RSA and RW primitives, at least if the PSS salt length is reasonably large. Our security proofs are based on already existing work by Bellare and Rogaway and by Coron, who examined signature schemes based on the original PSS encoding method.