LAMA: A secure lattice-based authentication scheme for cloud storage against misbehaved private key generator

The deployment of cloud services enables users to outsource their data to cloud servers and retrieve the target data efficiently. However, the application of quantum computers in clouds would be realized from the recent breakthrough results of quantum computers. Existing authentication schemes based on conventional hardness assumptions will be confronted with quantum attackers in the near future. A lattice-based authentication scheme resolves this tension. Although, existing lattice-based authentication schemes employing identity-based signcryption (IBS), the security against misbehaved private key generators (mPKG) is not well-considered, which may cause privacy issues in some application scenarios since the mPKG can generate the secret key for any given identity. This paper proposes an IBS-based authentication scheme for cloud storage dubbed LAMA that thwarts adversaries who have quantum computing power. We integrate the IBS scheme with the lattice-based cryptography, which is the variant of existing IBS-based authentication schemes and is post-quantum secure. We integrate identity certifying authority (ICA) with private key generator (PKG) to ensure security against mPKG. Our comprehensive security proof demonstrates that LAMA is indistinguishable against chosen plaintext attacks and secure against mPKG. We conduct a comprehensive performance evaluation of LAMA, which demonstrates the high efficiency of LAMA in terms of computation and communication overhead and proves that it can be easily deployed on low configured user devices.