A Parallel Signcryption Standard using RSA with PSEP

We present a proposed standard for signcryption (a joint signature and encryption primitive) using the Probabilistic Signature and Encryption Padding (PSEP) scheme. The standard supports signcrypting short and long messages, associated data (“labels”), and key reuse (a single RSA key suffices for both signcryption and designcryption). The proposed scheme is provably secure under the strongest known definitions of security for signcryption. Furthermore, the standard is backwards compatible with the existing PKCS#1 public key infrastructure, and provides support for senders and receivers with different RSA modulus lengths. We motivate the general use of the signcryption primitive with practical issues, and demonstrate an application to key exchange protocols such as that carried out by SSL. In particular, we suggest a key exchange protocol designed to minimize the round complexity and computational cost. We conclude with a brief analysis of various techniques that can be used to increase the efficiency of our signcryption primitive.