International Association
for Cryptologic Research

The quantum resistance Key Encapsulation Mechanism (PQC-KEM) design aims to replace cryptography in legacy security protocols. It would be nice if PQC-KEM were faster and lighter than ECDH or DH for easy migration to legacy security protocols. However, it seems impossible due to the temperament of the secure underlying problems in a quantum environment. Therefore, it makes reason to determine the threshold of the scheme by analyzing the maximum bandwidth the legacy security protocol can adapt. We specified the bandwidth threshold at 1,244 bytes based on IKEv2 (RFC7296), a security protocol with strict constraints on payload size in the initial exchange for secret key sharing. We propose TiGER that is an IND-CCA secure KEM based on RLWE(R). TiGER has a ciphertext (1,152bytes) and a public key (928 bytes) smaller than 1,244 bytes, even at the AES256 security level. To our knowledge, TiGER is the only scheme with such an achievement. Also, TiGER satisfies security levels 1, 3, and 5 of NIST competition. Based on reference implementation, TiGER is 1.7-2.6x faster than Kyber and 2.2-4.4x faster than LAC.