Recently, Islam and Biswas proposed a pairing-free identity-based authenticated group key agreement protocol for imbalanced mobile networks. However, in this letter, we point out that this protocol cannot resist passive attack, and cannot provide forward secrecy for joining operation and backward secrecy for leaving operation.

Identity Based Cryptography (IBC) is well known method in the field of security, however it has an inherent drawback of Key Escrow under which central key generation center is a sole issuing authority of private key and thus could misuse it. Our survey finds numerous solutions of key escrow; out of them secure key issuing protocol (SKIP) is most prominent. However, there are scopes for improvin...

Group key transfer protocols allow multiple parties to share a common secret key. They rely on a mutually trusted key generation center (KGC) that selects the key and securely distributes it to the authorized participants. Recently, Sun et al. proposed an authenticated group key transfer protocol based on secret sharing that they claim to be secure. We show that this is false: the protocol is s...

This paper revisits a public key cryptosystem which is based on finite string-rewriting systems. We consider a new approach for cryptanalysis of such proposals—the so-called completion attack. If a particular kind of weak key is generated, then a passive adversary is able to retrieve secret messages with a significant probability. Our idea can be applied to other rewriting based cryptosystems a...

This work uses enhanced symmetric key encryption algorithm, in which same structure of encryption and decryption procedure algorithm is used. In conventional encryption methods the key for encryption and decryption is same and remain secret. The algorithm uses key generation method by random number in algorithm for increasing efficiency of algorithm. The algorithm use key size of 512 bits for p...

HB and HB+ are a shared secret-key authentication protocols designed for low-cost devices such as RFID tags. HB+ was proposed by Juels and Weis at Crypto 2005. The security of the protocols relies on the learning parity with noise (LPN) problem, which was proven to be NP-hard. The best known attack on LPN by Levieil and Fouque [13] requires subexponential number of samples and sub-exponential n...

In modern network computing, authenticated group key agreement (AGKA) is important for conferencing. After Shamir [2] proposed the ID-based cryptosystem in 1984, the various applications on the ID-based cryptosystem have been actively studied, due to the simple key management complexity. For the AGKA, Choi et al. [16] proposed an ID-based authenticated group key agreement with bilinear maps, wh...

We present an extension of Wiener’s attack on small RSA secret decryption exponents [10]. Wiener showed that every RSA public key tuple (N, e) with e ∈ ∗ φ(N) that satisfies ed − 1 = 0 mod φ(N) for some d < 1 3 N 1 4 yields the factorization of N = pq. Our new method finds p and q in polynomial time for every (N, e) satisfying ex + y = 0 mod φ(N) with x < 1 3 N 1 4 and |y| = O(N− 3 4 ex). In ot...

Group Key Transfer (GKT) protocols allow multiple parties to share a common secret key: a trusted Key Generation Center (KGC) selects a uniformly random value that has never been used before and securely distributes it to the legitimate principals. The paper restricts to GKT based on secret sharing; it briefly reviews the security goals and the existing formal security models. We motivate our w...

The key schedule of the Data Encryption Standard is analyzed, and it is shown that the properties of the permuted choice PC-2 transformation and the number of bits that are left shifted during the key generation are critical for the security of the algorithm. More precisely, we were able to mount a low complexity related-key attack on DES with slightly modified key schedule although no related-...