Public Key Encryption Algorithm and the Random Oracle

Cryptographic theory has provided a potentially invaluable notion for cryptographic practice: the idea of provable security. Unfortunately, theoretical work often gains provable security only at the cost of effciency. Schemes like standard RSA are efficient but not provably secured. There are schemes who are provably secured but are not efficient. However, there are encryption schemes, for eg. El Gamal encryption, which are efficient and secured at the same time. There is a need to construct more encryption schemes which are provably secure, but also efficient.One of the approach use is through Random Oracles.