ABSTRACT
The introduction of public-key encryption marked a revolution in cryptography. Public-key techniques, in contrast, enable parties to communicate privately without having agreed on any secret information in advance. The fact that public-key encryption schemes allow anyone to act as a sender can be a drawback when a receiver only wants to receive messages from one specific individual. The important difference from the private-key setting is that the key-generation algorithm Gen outputs two keys instead of one. The public key pk is used for encryption, while the private key sk is used for decryption. Chosen-ciphertext attacks, in which an adversary is able to obtain the decryption of arbitrary ciphertexts of its choice, are a concern in the public-key setting just as they are in the private-key setting. A similar calculation can be used to measure the effect of hybrid encryption on the ciphertext length.
