Efficient and secure self-escrowed public-key infrastructures

A self-escrowed public key infrastructure (SE-PKI) combines the usual functionality of a public-key infrastructure with the ability to recover private keys given some trap-door information. We present an additively homomorphic variant of an existing SE-PKI for ElGamal encryption. We also propose a new efficient SE-PKI based on the ElGamal and Okamoto-Uchiyama cryptosystems that is more efficient than the previous SE-PKI. This is the first SE-PKI that does not suffer from a key doubling problem of previous SE-PKI proposals. Additionally, we present the first self-escrowed encryption schemes secure against chosen-ciphertext attack in the standard model. These schemes are also quite efficient and are based on the Cramer-Shoup cryptosystem, and the Kurosawa-Desmedt hybrid variant in different groups.