Can anyone explain to me what a trapdoor one-way permutation is? Is RSA a trapdoor one-way permutation?
Context: I was reading about ring signatures. On page 560, it describes steps to implementing a ring signature. I am confused by step 3, where $g()$ is a trap-door permutation. The paper briefly says that $g()$ is an RSA trap-door permutation. I thought that RSA was a public-key encryption protocol. Is RSA a trapdoor permutation?