A public-key encryption scheme with pseudo-random ciphertexts

This work presents a practical public-key encryption scheme that offers security under adaptive chosen-ciphertext attack (CCA) and has pseudo-random ciphertexts, i.e. ciphertexts indistinguishable from random bit strings. Ciphertext pseudo- randomness has applications in steganography. The new scheme features short ciphertexts due to the use of elliptic curve cryptography, with ciphertext pseudo- randomness achieved through a new key encapsulation mechanism (KEM) based on elliptic curve Diffie-Hellman with a pair of elliptic curves where each curve is a twist of the other. The public-key encryption scheme resembles the hybrid DHIES construction; besides by using the new KEM, it differs from DHIES in that it uses an authenticate-then-encrypt (AtE) rather than encrypt-then-authenticate (EtA) approach for symmetric cryptography.