In this paper, we present an adaptively secure identity-based broadcast encryption system featuring constant sized ciphertext in the standard model. The size of the public key and the private keys of our system are both linear in the maximum number of receivers. In addition, our system is fully collusion-resistant and has stateless receivers. Compared with the state-of-the-art, our scheme is well optimized for the broadcast encryption. The computational complexity of decryption of our scheme depends only on the number of receivers, not the maximum number of receivers of the system. Technically, we employ dual system encryption technique and our proposal offers adaptive security under the general subgroup decisional assumption. Our scheme demonstrates that the adaptive security of the schemes utilizing a composite order group can be proven under the general subgroup decisional assumption, while many existing systems working in a composite order group are secure under multiple subgroup decision assumptions. We note that this finding is of an independent interest, which may be useful in other scenarios.

In this paper, we propose an efficient method for extracting simple low-degree equations (e.g. quadratic ones) in addition to the linear ones, obtainable from the original cube attack by Dinur and Shamir at EUROCRYPT 2009. This extended cube attack can be successfully applied even to cryptosystems in which the original cube attack may fail due to the attacker's inability in finding sufficiently many independent linear equations. As an application of our extended method, we exhibit a side channel cube attack against the PRESENT block cipher using the Hamming weight leakage model. Our side channel attack improves upon the previous work of Yang, Wang and Qiao at CANS 2009 from two aspects. First, we use the Hamming weight leakage model which is a more relaxed leakage assumption, supported by many previously known practical results on side channel attacks, compared to the more challenging leakage assumption that the adversary has access to the "exact" value of the internal state bits as used by Yang et al. Thanks to applying the extended cube method, our attack has also a reduced complexity compared to that of Yang et al. Namely, for PRESENT-80 (80-bit key variant) as considered by Yang et al., our attack has a time complexity 216 and data complexity of about 213 chosen plaintexts; whereas, that of Yang et al. has time complexity of 232 and needs about 215 chosen plaintexts. Furthermore, our method directly applies to PRESENT-128 (i.e. 128-bit key variant) with time complexity of 264 and the same data complexity of 213 chosen plaintexts.

In this paper, we further study the key schedule of the AES algorithm and present some repeated differential properties of the AES-128 and AES-256 key schedules. We define the concept of repeated differential pattern for the AES 128 key schedule, and the notion of double-sized repeated differential pattern for the AES-256 key schedule. We show that if we use the key schedule to expand two 128-bit (or 256-bit) secret keys with the repeated differential pattern (or double-sized repeated differential pattern), the resultant 10 round (or 14-round) subkeys have a large number of bytes in common and the differential pattern has strong repeated features.

IP spoofing remains a problem today in the Internet. In this paper, a new system called Inter-Domain Routing Validator Based Spoofing Defence System (SDS) for filtering spoofed IP packets is proposed. SDS uses efficient symmetric key message authentication code (UMAC) as its tag to verify that a source IP address is valid. Different ASes border routers obtain a shared key via the Inter-Domain Routing Validator (IRV) servers which will manage the secret keys and exchange keys among different ASes via security communication channel. SDS is efficient, secure and easy to cooperate with other defence mechanisms.

Constructions of square, maximum rate complex orthogonal space–time block codes (CO STBCs) are well known, however codes constructed via the known methods include numerous zeros, which impede their practical implementation. By modifying the Williamson and Wallis-Whiteman arrays to apply to complex matrices, we propose two methods of construction ofsquare, order-$4n$CO STBCs fromsquare, order-$n$codes which satisfy certain properties. Applying the proposed methods, we constructsquare,maximum rate, order-8 CO STBCs with no zeros, such that the transmitted symbols are equally dispersed through transmit antennas. Those codes, referred to as theimproved square CO STBCs, have the advantages that the power is equally transmitted via each transmit antenna during every symbol time slot and that a lower peak-to-average power ratio (PAPR) is required to achieve the same bit error rates as the conventional CO STBCs with zeros.

This letter proposes a simple but highly efficient technique to jointly utilize space, time, and polarization diversities. The technique is based on extending orthogonal space-time block codes into the quaternion domain and utilizing a description of the dual-polarized signal by means of quaternions, which are a generalization of complex numbers. In the given example, the achievable performance gain for two transmit and one receive antennas is approximately 6 dB at a bit error rate of 10-4when compared with the Alamouti code.

Constructions of square, maximum rate complex orthogonal space-time block codes (CO STBCs) are well known, however codes constructed via the known methods include numerous zeros, which impede their practical implementation. By modifying the Williamson and Wallis-Whiteman arrays to apply to complex matrices, we propose two methods of construction or square, order-4n CO STBCs from square, order-n codes, which satisfy certain properties. Applying the proposed methods, we construct square, maximum rate, order-8 CO STBCs with no zeros, such that the transmitted symbols equally disperse through transmit antennas. Those codes, referred to as the improved square CO STBCs, have the advantages that the power is equally transmitted via each transmit antenna during every symbol time slot and that a lower peak-to-mean power ratio per each antenna is required to achieve the same bit error rates as for the conventional CO STBCs with zeros

Although the generation of correlated Rayleigh fading envelopes has been intensively considered in the literature, all conventional methods have their own particular shortcomings, which seriously impedes their applicability. A very general, straightforward algorithm is proposed for the generation of an arbitrary number of Rayleigh envelopes with any desired, equal or unequal power in wireless channels, either with or without Doppler frequency shifts. The proposed algorithm can be applied in the case of spatial correlation, such as with antenna arrays in multiple input multiple output (MIMO) systems, or spectral correlation between random processes, as in orthogonal frequency division multiplexing (OFDM) systems. It can also be used for generating correlated Rayleigh fading envelopes in either discrete-time instants or a real-time scenario. Besides being more generalized, our proposed algorithm is more precise, while overcoming all the shortcomings of conventional methods.

Abstract Orthogonal bipolar spreading sequences are used in direct sequence code division multiple access (DS‐CDMA) systems for both spectrum spreading and channel separation. The most commonly used sequences are Walsh–Hadamard sequences of lengths being an integer power of 2. A construction based on Williamson's arrays leading to sequences of lengths N≡4 (mod 8) is presented in the paper. Aperiodic correlation characteristics, for example sequence sets of lengths 12–252 are presented. The correlation properties of the sequence sets are later improved using a diagonal modification technique. Copyright © 2003 John Wiley & Sons, Ltd.

The security of ordinary digital signature schemes relies on a computational assumption. Fail-stop signature schemes provide security for a sender against a forger with unlimited computational power by enabling the sender to provide a proof of forgery if it occurs. In this paper we give an efficient fail-stop signature scheme that uses two hard problems, discrete logarithm and factorization, as the basis of a receiver's security. We show that the scheme has provable security against adaptively chosen message attack, and is the most efficient scheme with respect to the ratio of the message length to the signature length. The scheme provides an efficient solution to signing messages up to 1881 bits.

Reliable authentication of communicating entities is essential for achieving security in a distributed computing environment. The design of such systems as Kerberos, SPX and more recently KryptoKnight and Kuperee, have largely been successful in addr

A (t, w) threshold scheme is a method for sharing a secret among w shareholders so that the collaboration of at least t shareholders is required in order to reconstruct the shared secret. This paper is concerned with the re-use of shares possessed by shareholders in threshold schemes. We propose a simple (t, w) threshold scheme based on the use of cryptographically strong pseudo-random functions and universal hash functions. A remarkable advantage of the scheme is that a shareholder can use a single string in the share of many different secrets; in particular, a shareholder need not be given a new share each time a new secret is to be shared.

We prove that the conjecture on Bent sequences stated in the paper written by Kumar, Scholtz and Welch (see J. Combinatorial Theory, Ser A, vol.40, p.90-107, 1985) is false.>

Substitution boxes (S-boxes) are a crucial component of DES-like block ciphers. This research addresses problems with previous approaches towards constructing S-boxes, and proposes a new definition for the robustness of S-boxes to differential cryptanalysis, which is the most powerful cryptanalytic attack known to date. A novel method based on group Hadamard matrices is developed to systematically generate S-boxes that satisfy a number of critical cryptographic properties. Among the properties are the high nonlinearity, the strict avalanche characteristics, the balancedness, the robustness against differential cryptanalysis, and the immunity to linear cryptanalysis. An example is provided to illustrate the S-box generating method.

Three methods for strengthening public key cryptosystems in such a way that they become secure against adaptively chosen ciphertext attacks are presented. In an adaptively chosen ciphertext attack, an attacker can query the deciphering algorithm with any ciphertext except for the exact object ciphertext to be cryptanalyzed. The first strengthening method is based on the use of one-way hash functions, the second on the use of universal hash functions, and the third on the use of digital signature schemes. Each method is illustrated by an example of a public key cryptosystem based on the intractability of computing discrete logarithms in finite fields. Security of the three example cryptosystems is formally proved. Two other issues, namely, applications of the methods to public key cryptosystems based on other intractable problems and enhancement of information authentication capability to the cryptosystems, are also discussed.>

The application of coding theory to security scenarios is studied. Authentication systems are introduced that are based on algebraic codes and provide high protection against an intruder's impersonation and substitution attacks. It is shown that a subliminal channel can be embedded into these systems and that there is a trade-off between the authentication capability, subliminal capacity, and error protection capability.>

The Australia wide eftpos systems was developed by the Australian Retail Banks to meet Australian conditions including a small population, which overwhelmingly uses cash for transactions, a small number of banks capable of “exchange of value” settlements and enormous distances. This paper discusses the system that has evolved first involving only ATM’s and banks, then extending to POS systems for retailers and non bank financial institutions. These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

The concept of orthogonal design is extended to higher dimensions. A properg-dimensional design[d_{ijk \cdots \upsilon}]is defined as one in which all parallel(g-1)-dimensional layers, in any orientation parallel to a hyper plane, are uncorrelated. This is equivalent to the requirement thatd_{ijk \cdots \upsilon} \in \{0, \pm x_{1}, \cdots , \pm x_{t} \}, wherex_{1}, \cdots , x_{t}are commuting variables, and that\sum_{p} \sum_{q} \sum_{r} \cdots \sum_{y} d_{pqr \cdots ya} d_{pqr \cdots yb} = \left( \sum_{t} s_{i}x_{i}^{2} \right)^{g-1} \delta ab,where(s{1}, \cdots , s{t})are integers giving the occurrences of\pm x_{1}, \cdots , \pm x_{t}in each row and column (this is called the type(s_{1}, \cdot ,s_{t})^{g-1})and(pqr \cdots yz)represents all permutations of(ijk \cdots \upsilon). This extends an idea of Paul J. Shlichta, whose higher dimensional Hadamard matrices are special cases withx_{1}, \cdots , x_{t} \in \{1,- 1\}, (s_{1}, \cdots, s_{t})=(g), and(\sum_{t}s_{i}x_{i}^{2})=g. Another special case is higher dimensional weighing matrices of type(k)^{g}, which havex_{1}, \cdots , x_{t} \in \{0,1,- 1\}, (s_{1}, \cdots, s_{t})=(k), and(\sum_{t}s_{i}x_{i}^{2})=k. Shlichta found properg-dimensional Hadamard matrices of size(2^{t})^{g}. Proper orthogonal designs of type