Cipher

Abstract: (MATH) In the bounded-storage model for information-theoretically secure encryption and key-agreement one can prove the security of a cipher based on the sole assumption that the adversary's storage capacity is bounded, say by s bits, even if her computational power is unlimited. Assume that a random t-bit string R is either publicly available (e.g. the signal of a deep space radio source) or broadcast by one of the legitimate parties. If s$xi;t, the adversary can store only partial information about R. The legitimate sender Alice and receiver Bob, sharing a short secret key K initially, can therefore potentially generate a very long n-bit one-time pad X with n»|K| about which the adversary has essentially no information, thus at first glance apparently contradicting Shannon's bound on the key size of a perfect cipher.All previous results in the bounded-storage model were partial or far from optimal, for one of the following reasons: either the secret key K had in fact to be longer than the derived one-time pad, or t had to be extremely large (tρns), or the adversary was assumed to be able to store only actual bits of R rather than arbitrary s bits of information about R, or the adversary could obtain a non-negligible amount of information about X.In this paper we prove the first non-restricted security result in the bounded-storage model, exploiting the full potential of the model: K is short, X is very long (e.g. gigabytes), t needs to be only moderately larger than s, and the security proof is optimally strong. In fact, we prove that s/t can be arbitrarily close to 1 and hence the storage bound is essentially optimal.

Abstract: The existing DNA based image cryptosystems, their DNA coding scheme just employs four DNA symbols, namely A, T, C and G, to represent the four binary two-tuples, namely 00b, 01b, 10b and 11b, respectively. And the used DNA computing algorithms, such as DNA addition and subtraction, are essentially the binary modulo 2 addition and XOR operations without any meanings of genetic engineering, which cannot apply to the DNA computer for processing. So, this paper discussed the DNA coding of image and proposed a new DNA join operation. And the complementary operation of DNA code instead of the complementary operation of binary number is used in the proposed. The piecewise linear chaotic map was employed to generate the key stream. Then, a new DNA based image cryptosystem including two rounds of DNA diffusion and DNA confusion was proposed, which can be rapidly implemented in the DNA computer. The image cryptosystem was simulated with an electronic computer, and the results show that the proposed system possesses the characteristics of large key space, good statistical properties of cipher images, high sensitivities of key and plain images and big information entropy. Therefore, the proposed image cryptosystem is a candidate for the future secure communication application to the DNA computer.

Abstract: The naive implementation of AES is known to be vulnerable to Differential Fault Analysis (DFA). We can findthe key of AES-128 (AES with 128-bit key) with one pair of correct and faulty cipher texts. Recently several works on the extension of the attack to AES with 192 and 256-bit key have been published. Due to the longer key size and the characteristic of AES key schedule, we need subtle caution in attacking AES-192and AES-256. We propose new DFA against AES with 192 and256-bit key. We could retrieve AES-192 key with two pairs of correct and faulty cipher texts. With three pairs we could succeed in finding the key of AES-256. These are the minimal faults among the existing methods.