Constructing practical signcryption KEM from standard assumptions without random oracles

Abstract

We present a direct construction for signcryption Key Encapsulation Mechanism (KEM) without random oracles under standard complexity assumptions. Chosen-ciphertext security is proven in the standard model under the DBDH assumption, and unforgeability is proven in the standard model under the CDH assumption. The proof technique allows us to achieve strong unforgeability from the weakly unforgeable Waters signature. The validity of the ciphertext of our signcryption KEM can be verified publicly, without knowledge of the decryption key. © 2013 Springer-Verlag.