Related-key attack (RKA) is a kind of side-channel attack considered for kinds of cryptographic primitives, such as public key encryption, digital signature, pseudorandom functions etc. However, we note that the RKA-security seems to be not considered for identity-based signature (IBS), which is an important primitive for identity-based cryptography and proposed by Shamir in 1984. In this paper, for the first time, we introduce the RKA security into IBS schemes and try to define the security model for it. More specifically, we consider the RKA occurs in the users' signing key or the master key of the key-generation center (KGC), which derives two kinds of RKA securities for IBS. Meanwhile, we illustrate that the most efficient Schnorr-like IBS scheme proposed by Galindo and Garcia is RKA-insecure by launching a simple RKA. However, a slight modification of it yields a RKA-secure IBS scheme, for which we give the detailed security proof in the random oracle. Finally, the performance analysis shows that the modified scheme is still extremely efficient but has higher security.

Homomorphic signature is an extremely important public key authentication technique for network coding to defend against pollution attacks. As a public key cryptographic primitive, it also encounters the same problem of how to confirm the relationship between some public key pk and the identity ID of its owner. In the setting of distributed network coding, the intermediate and destination nodes need to use the public key of source node S to check the validity of vector-signature pairs. Therefore, the binding of S and its corresponding public key becomes crucial. The popular and traditional solution is based on certificates which are issued by a trusted certification authority (CA) center. However, the generation and management of certificates is extremely cumbersome. Hence, in recent work, Lin et al. proposed a new notion of identity-based homomorphic signature, which intends to avoid using certificates. But the key escrow problem is inevitable for identity-based primitives. In this article, we propose another new notion (for network coding): certificateless homomorphic signature (CLHS), which is a compromise for the above two techniques. In particular, we first describe the definition and security model of certificateless homomorphic signature. Then based on bilinear map and the computational Diffie-Hellman (CDH) assumption, give a concrete implementation and detailedly analyze its security. Finally, performance analysis illustrates that our construction is practical.

Storing multi-copy of data file on multi-cloud may be useful in some practical contexts. How to ensure the integrity of a user’s multi-copy becomes very important in this case. In recent work, Li et al. proposed an efficient “identity-based” auditing protocol (LYZ-protocol, for short) to achieve this goal. The “identity-based” property guarantees that the resulting primitive does not rely on PKI to manage certificates. However, in this letter, we note that the performances of this protocol can be further improved. More precisely, by introducing a new hash function modeled as a random oracle, the communication costs of original LYZ-protocol can be greatly reduced. In addition, the building block of a traditional signature scheme used in this protocol results in the entire protocol not being completely identity-based, and thus it may still bear the burden of managing certificates. Therefore, by replacing this signature with an identity-based scheme, we can obtain a completely identity-based protocol. Finally, the performance analysis shows that the modified LYZ-protocol outperforms the original one.

Recently, Lin et al. proposed a new primitive: Identity-based (IB) homomorphic signature scheme, IEEE Access, 6(2018), pp. 20632-20639, and presented an ingenious implement by using any IB-signature scheme as building block. In this paper, we consider a new type attack on their scheme: Related-key attack (RKA), which is introduced by Bellare and Kohno in 2003, and widely considered for kinds of cryptographic primitives. Specifically, for the first time, we define the RKA security of IB-homomorphic signature scheme. By modifying the signing secret key as its linear form, we prove that Lin et al.’s IB-homomorphic signature scheme is not RKA secure. But a slight modification of it yields a RKA secure one under the original assumptions. We also present the security proof in detail. However, we remark that the reason why RKA on Lin et al.’s scheme can be successful lies in that RKA is outside of their security model. Finally, the numerical analysis and experimental results demonstrate that our modified scheme does not distinctly decrease the computational efficiency of Lin et al.’s scheme.

Semi-quantum cryptography communication stipulates that the quantum user has complete quantum capabilities, and the classical user has limited quantum capabilities, only being able to perform the following operations: (1) measuring and preparing qubits with a Z basis and (2) returning qubits without any processing. Secret sharing requires participants to work together to obtain complete secret information, which ensures the security of the secret information. In the semi-quantum secret sharing (SQSS) protocol, the quantum user Alice divides the secret information into two parts and gives them to two classical participants. Only when they cooperate can they obtain Alice’s original secret information. The quantum states with multiple degrees of freedom (DoFs) are defined as hyper-entangled states. Based on the hyper-entangled single-photon states, an efficient SQSS protocol is proposed. The security analysis proves that the protocol can effectively resist well-known attacks. Compared with the existing protocols, this protocol uses hyper-entangled states to expand the channel capacity. The transmission efficiency is 100% higher than that of single-degree-of-freedom (DoF) single-photon states, providing an innovative scheme for the design of the SQSS protocol in quantum communication networks. This research also provides a theoretical basis for the practical application of semi-quantum cryptography communication.