Building Better Signcryption Schemes with Tag-KEMs

Signcryption schemes aim to provide all of the advantages of simultaneously signing and encrypting a message. Recently, Dent [8, 9] and Bjørstad [4] investigated the possibility of constructing provably secure signcryption schemes using hybrid KEM-DEM techniques [7]. We build on this work by showing that more efficient insider secure hybrid signcryption schemes can be built using tag-KEMs [1]. To prove the effectiveness of this construction, we will provide several examples of secure signcryption tag-KEMs, including a brand new construction based on the Chevallier-Mames signature scheme [5] which has the tightest known security reductions for both confidentiality and unforgeability.