The development of Wireless Body Area Network (WBAN) and Wearable Health Monitoring Systems (WHMS) play a key role in healthcare monitoring. WBAN includes medical sensors that monitor vital signs of patients, collect data and usually transmit them to medical servers via wireless channels. Therefore, the patient’s sensitive information sent over the channel can be vulnerable to various attacks. Hence, designing lightweight authentication security protocols for these systems with the lowest computational and communication costs has become a major challenge. Recently, Sowjanya et al. (2020) presented a lightweight authentication scheme for WHMS based on Elliptic Curve Cryptography (ECC), which provides optimal security features and low storage, communication and computational costs. In this paper, the security of their scheme is evaluated and passive insider secret disclosure and replay attacks against their scheme are presented. It is obvious that other attacks such as desynchronization attack and impersonation attack can be applied to this protocol by obtaining the secret value of network manager. The complexity of our proposed attacks is just one run of the protocol and their success probability equals to one. Finally, by remedying the Sowjanya et al. (2020) ’s protocol, a lightweight ECC-based authentication scheme called ECCPWS is proposed. Moreover, the proposed protocol’s security proof is performed via informal methods and also formally through Real-Or-Random (ROR) model, BAN logic, Scyther and AVISPA tools. The security verification results of ECCPWS show that the ECCPWS has complete security against various security vulnerabilities and attacks.

Committee-based permissionless blockchain approaches overcome single leader consensus protocols’ scalability issues by partitioning the outstanding transaction set into shards and selecting multiple committees to process these transactions in parallel. However, by design, shard-based blockchain solutions are vulnerable to Sybil attacks. An adversary with enough computational/hash power can easily manipulate the consensus protocol by generating multiple valid node identifiers/IDs (i.e., multiple Sybil committee members).Despite the straightforward nature of these attacks, they have not been systematically investigated. This article fills this research gap by analyzing Sybil attacks in shard-based consensus of proof-of-work blockchain systems. Specifically, we provide a detailed analysis for Elastico, one of the prominent shard-based blockchain models. We show that the proof-of-work technique used for ID generation in the initial phase of such protocols is vulnerable to Sybil attacks when an adversary (could be a group of colluding nodes) possesses enough hash power. We analytically derive conditions for two different Sybil attacks and perform numerical simulations to validate our theoretical results under various parameters. Further, we utilize the BlockSim simulator to validate our mathematical computation, and results confirm the correctness of the analysis.

Abstract Digital signature schemes are used for the authentication and verification of signatures. The Courtois–Finiasz–Sendrier (CFS) digital signature is a well‐known code‐based digital signature scheme based on the Niederreiter cryptosystem. However, it is not widely used due to the computation time of the signing algorithm. Most code‐based digital signature schemes are based on the Niederreiter cryptosystem. This paper proposes a new code‐based digital signature that is based on the McEliece cryptosystem. Key generation, signing, and verification algorithms are presented. The key generation algorithm constructs a public key using random inverse matrices. The signing algorithm has lower complexity and requires less computation time than the CFS scheme to sign a document. The verification algorithm is able to detect forgeries. It is shown that the proposed scheme is secure against public key structural attacks.

Abstract Certificateless public key cryptography (CL-PKC) promises a practical resolution in establishing practical schemes, since it addresses two fundamental issues, namely the necessity of requiring certificate managements in traditional public key infrastructure (PKI) and the key escrow problem in identity-based (ID-based) setting concurrently. Signcryption is an important primitive that provides the goals of both encryption and signature schemes as it is more efficient than encrypting and signing messages consecutively. Since the concept of certificateless signcryption (CL-SC) scheme was put forth by Barbosa and Farshim in 2008, many schemes have been proposed where most of them are provable in the random oracle model (ROM) and only a few number of them are provable in the standard model. Very recently, Luo and Wan (Wireless Personal Communication, 2018) proposed a very efficient CL-SC scheme in the standard model. Furthermore, they claimed that their scheme is not only more efficient than the previously proposed schemes in the standard model, but also it is the only scheme which benefits from known session-specific temporary information security (KSSTIS). Therefore, this scheme would indeed be very practical. The contributions of this paper are 2-fold. First, in contrast to the claim made by Luo and Wan, we show that unfortunately Luo and Wan made a significant error in the construction of their proposed scheme. While their main intention is indeed interesting and useful, the failure of their construction has indeed left a gap in the research literature. Hence, the second contribution of this paper is to fill this gap by proposing a CL-SC scheme with KSSTIS, which is provably secure in the standard model.

In a designated verifier signature (DVS) scheme, the validity of the signature can only be checked by a designated entity chosen by the signer. Furthermore, the designated entity cannot convince a third party that the signature is generated by the signer. A multi‐designated verifiers signature (MDVS) scheme is an extension of a DVS which includes multiple designated verifiers. To the best of the authors’ knowledge, there are two existing patterns for an MDVS scheme. In the first pattern, every verifier of the set of designated verifiers can check the validity of the signature independently. In the second pattern, the cooperation of all designated verifiers is required for checking the validity of the signature. In this study, the authors propose a generic new pattern for an MDVS scheme in which a threshold number of the set of designated verifiers can check the validity of the signature. They also present a concrete MDVS scheme with threshold verifiability in the standard model. Moreover, they compare their scheme with other existing MDVS schemes. Finally, they briefly explain scenarios in which the proposed pattern can be applicable.

Abstract PRESENT and MIBS are two lightweight block ciphers that are suitable for low resource devices such as radio‐frequency identification tags. In this paper, we present the first biclique cryptanalysis of MIBS block cipher and a new biclique cryptanalysis of PRESENT block cipher. These attacks are performed on full‐round MIBS‐80 and full‐round PRESENT‐80. Using matching without matrix technique in the attack on MIBS and choosing a sub‐key space of an internal round for key division eventuate to reduce the security of this cipher by 1bit, while the data complexity of attack is 252 chosen plaintext. The attack on PRESENT‐80 has a data complexity of at most 222 chosen plaintext and computational complexity of 279.34 encryption that both complexities are lower than of other cryptanalyses of full‐round PRESENT‐80 so far. Also, in this paper, we use early abort technique to efficiently filter out wrong keys in matching phase of biclique attack of PRESENT‐80. Copyright © 2015 John Wiley & Sons, Ltd.

A new joint cryptography‐channel coding technique is introduced which employs punctured quasi‐cyclic‐low density parity check (QC‐LDPC) codes obtained from extended difference families. The absence of permutation and scrambling matrices reduces the key size compared with similar code‐based cryptosystems, while having an acceptable level of security. The main advantage of this system is that, provided the system parameters are chosen appropriately, even if the code employed is revealed the system remains secure. Performance results are presented which show that the punctured code outperforms a random low density parity check (LDPC) code of the same length and rate.

Camellia, a 128-bit block cipher that has been accepted by ISO/IEC as an international standard, is increasingly being used in many cryptographic applications. In this study, the authors present a new impossible differential attack on a reduced version of Camellia-256 without FL/FL−1 functions and whitening. First, the authors introduce a new extension of the hash table technique and then exploit it to attack 16 rounds of Camellia-256. When, in an impossible differential attack, the size of the target subkey space is large and the filtration, in the initial steps of the attack, is performed slowly, the extended hash table technique will be very useful. The proposed attack on Camellia-256 requires 2124.1 known plaintexts and has a running time equivalent to about 2249.3 encryptions. In terms of the number of attacked rounds, our result is the best published attack on Camellia-256.

One of the most important structures used in modern block ciphers is the substitution–permutation network (SPN) structure. Many block ciphers with this structure widely use Maximun Distance Separable (MDS) matrices over finite fields as their diffusion layers, for example, advanced encryption standard (AES) uses a 4×4 MDS matrix as the main part of its diffusion layer and the block cipher Khazad has an involutory 8×8 matrix. In this study, first a construction is proposed for a 4×4 linear diffusion layer that can intermix four words of arbitrary size with branch number 5. Then extend this idea for 8×8 diffusion layer using low-cost linear functions. In this construction, first, certain binary linear combinations of inputs are fed into two or three different invertible linear functions and then combined using XOR operation. In order to show the efficiency of the proposed diffusion layer, the authors exploit it in a nested SPN structure and compare its efficiency with some well-known diffusion layers such as the diffusion layer of Hierocrypt.