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A new optical security system for image encryption based on a nonlinear joint transform correlator (JTC) in the Fresnel domain (FrD) is proposed. The proposal of the encryption process is a lensless optical system that produces a real encrypted image and is a simplified version of some previous JTC-based encryption systems. We use a random complex mask as the key in the nonlinear system for the purpose of increasing the security of the encrypted image. In order to retrieve the primary image in the decryption process, a nonlinear operation has to be introduced in the encrypted function. The optical decryption process is implemented through the Fresnel transform and the fractional Fourier transform. The security system proposed in this paper preserves the shift-invariance property of the JTC-based encryption system in the Fourier domain, with respect to the lateral displacement of the key random mask in the decryption process. This system shows an improved resistance to chosen-plaintext and known-plaintext attacks, as they have been proposed in the cryptanalysis of the JTC encrypting system. Numerical simulations show the validity of this new optical security system. (C) 2014 Optical Society of America

Absolute lower limits to the cost of cryptanalytic attacks are quantified, via a theory of guesswork. Conditional guesswork naturally expresses limits to known and chosen plaintext attacks. New inequalities are derived between various forms of guesswork and variation distance. The machinery thus offers a new technique for establishing the security of a cipher: When the work-factor of the optimal known or chosen plaintext attack against a cipher is bounded below by a prohibitively large number, then no practical attack against the cipher can succeed. As an example, we apply the technique to iterated cryptosystems, as the Markov property which results from an independent subkey assumption makes them particularly amenable to analysis.

Wagner, Goldberg and Briceno have recently published an attack [2] on what they believe to be Comp128, the GSM A3A8 authentication function [1]. Provided that the attacker has physical access to the card and to its secret PIN code (the card has to be activated), this chosen plaintext attack recovers the secret key of the personalized SIM (Secure Identification Module) card by inducing collisions on the second (out of 40) round of the compression function. In this paper we suggest two different approaches to strengthen the alleged Comp128 algorithm with respect to this attack. An evaluation of the number of chosen plaintexts and the new complexity of the attack are given.

Decorrelated Fast Cipher(DFC),LOKI97 and MAGENTA are candidates for the Advanced Encryption Standard(AES). In this paper we analyze their security respectively. Since cryptographic properties of the confusion permutation of DFC are weak, its security depends on its subkey addition completely. It seems that LOKI97 is not stronger than LOKI89 and LOKI91. Because of characteristics of the round function, LOKI97 is susceptible to linear cryptanalysis for some keys. MAGENTA is a Feistel cipher with only 6 rounds and its key schedule is very simple. Based on these limitations, we present a chosen plaintext attack against it using 264 chosen plaintexts. In conclusion, we do not think DFC, LOKI97 and MAGENTA are qualified candidates for the AES.

The conference key distribution problem over a broadcast channel, i.e. distribution of a key to a set of recipients by a central authority, can be solved by true broadcasting using threshold schemes. This paper gives a security analysis of this approach. After describing succesful attacks on two special implementations of true broadcasting schemes, a slightly different scheme is shown to be provably secure under some well-known cryptographic assumptions. As an application of the threshold scheme approach, a subliminal channel free scheme is given which can be used e.g. in Pay-TV systems.

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In this paper we analyse SAFER K-64 and show a weakness in the key schedule. It has the effect that for almost every key K, there exists at least one different key K*, such that for many plaintexts the outputs after 6 rounds of encryption are equal. The output transformation causes the ciphertexts to differ in one of the 8 bytes. Also, the same types of keys encrypt even more pairs of plaintexts different in one byte to ciphertexts different only in the same byte. This enables us to do a related-key chosen plaintext attack on SAFER K-64, which finds 8 bits of the key requiring from 244 to about 247 chosen plaintexts.While our observations may have no greater impact on the security of SAFER K-64 when used for encryption in practice, it greatly reduces the security of the algorithm when used in hashing modes, which is illustrated. We give collisions for the well-known secure hash modes using a block cipher. Also we give a suggestion of how to improve the key schedule, such that our attacks are no longer possible.

The optical cryptosystem based on phase-shifting interferom- etry (PSI) is one of the most interesting optical cryptographic schemes in recent years. However, we find that the PSI technique provides an attrac- tive method to record the ciphertext, but contributes little to the security level of the cryptosystem. From the cryptanalysis point of view, in a cer- tain simplified case, an attacker is only required to crack two equivalent decryption keys instead of the original random phase keys and geometric key. Moreover, a chosen-plaintext attack method is proposed, in which an impulse function is chosen as a known plaintext. By using this attack, the attacker can effectively recover any plaintext from the corresponding ciphertext. The validity of the attack is verified by computer simulations. C

From the perspective of optical cryptanalysis, we propose a method of chosen-plaintext attack against the optical encryption scheme based on joint transform correlator (JTC) architecture. By implementing this attack, an opponent can access the encryption key with the help of the pre-knowledge of a special chosen plaintext and the corresponding ciphertext. It indicates that the optical encryption scheme based on the JTC architecture is vulnerable to chosen-plaintext attack, even though introducing a nonlinear operation into the encryption transform. The validity of this attack is verified by numerical simulations.

In this paper we examine the redesign of LOKI, LOKI 91 proposed in [5]. First it is shown that there is no characteristic with a probability high enough to do a successful differential attack on LOKI 91. Secondly we show that the size of the image of the F-function in LOKI 91 is 8/13×232. Finally we introduce a chosen plaintext attack that reduces an exhaustive key search on LOKI 91 by almost a factor 4 using 233+2 chosen plaintexts.

The security of DES-style block ciphers rests largely upon their non-linear S-boxes. If different pairs of input data and key can produce identical inputs to all of a cipher's S-boxes, then for those pairs the system is weakened. A technique is described here which enables a cryptanalyst to find how many of these pairs, if any, exist for a given cryptosystem, and how to exploit those pairs under a chosen plaintext attack.

Recently，a large number of chaotic cryptosystems have been proposed，yet many of them have the drawbacks of lack of robustness and security. In this paper，we point out the weakness of a very recent block cipher algorithm which is based on the chaotic map and give the improved scheme of it. We provide the chosen plaintext attack to recover the permuted plaintext string. It is shown that the generation mechanism of binary sequences which depends on the key but not on the plaintext facilitates leakage of information and is vulnerable to attacks. Based on such a fact，we give the improved scheme to achieve higher security.

This paper analyzes the security of double random phase encoding in fresnel domain from the viewpoint of cryptoanalysis. We demonstrate the encryption system is vulnerable to chosen-plaintext attack with a prior knowledge of diffraction distance and wavelength. With this attack an opponent can access double random phase keys with the help of the impulse functions as chosen plaintext. The significant feature of proposed attack is that the decryption process is lossless. Numerical simulations show good agreement with theoretical analysis.

A chosen plaintext attack is presented for constructing all the private keys of cryptosystems based on array codes.

Public-key algebraic encryption (PUAE) has certain advantages that make it attractive in some applications. Variants of PUAE for private-key algebraic encryption (PRAE); have been proposed subsequently. PRAE is proven to be insecure under chosen plaintext attack. In the paper, some invariants of PRAE are studied, and a private-key cryptosystem based on concatenation of codes is proposed and analysed. The new system is, composed of short-length codes and is designed to avoid the weaknesses in other PRAE systems. The system looks secure against known attacks. Some methods to improve the system information rate and security are also suggested.

The Microsoft BASIC (MBASIC) interpreter provides a command which protects the program currently in memory by saving it, on disk, in an encrypted format. A user can RUN such a protected program, but cannot access the source program. A chosen-plaintext attack was used to break the encoding; the encryption method could be derived easily from the enciphering of carefully chosen plaintext programs. As a result, a pair of MBASIC programs able to decrypt a protected program for any interpreter was developed. Further, it is shown that a secure system can never be realized, whichever encryption method is used.

A probabilistic method is presented which cryptanalyzes any N key cryptosystem in N^{2/3} operational with N^{2/3} words of memory (average values) after a precomputation which requires N operations. If the precomputation can be performed in a reasonable time period (e.g, several years), the additional computation required to recover each key compares very favorably with the N operations required by an exhaustive search and the N words of memory required by table lookup. When applied to the Data Encryption Standard (DES) used in block mode, it indicates that solutions should cost between 1 and 100 each. The method works in a chosen plaintext attack and, if cipher block chaining is not used, can also be used in a ciphertext-only attack.

The attractors in many fractional-order chaotic systems have more complex dynamics than their integer-order systems. Consequently, there is a recent trend of exploring fractional chaotic systems for the design of image cryptosystems. The fractional derivative orders can act as part of secret key. Recently, an image encryption algorithm is suggested based on synchronized fractional-order chaotic systems. In this paper, a security appraisal is actioned to evince that the encryption algorithm is completely breakable under chosen-plaintext attack, has no mandatory plaintext sensitivity, and unsafe. Moreover, an enhanced version of encryption scheme is accounted to improve its attack defensibleness, plaintext sensitivity and inherent encryption strength. Experimental analyses are exercised and statistical results are catered to manifest the improved performance. The anticipated enhanced version has high security, consistency and practicability for encryption of digital images.

We present a chosen plaintext attack on the NTRU encryption system. We assume that the attacker can detect wrap errors, that the blinding polynomial is generated from three parts (as specified in the standards) and that the attacker has a large database of carefully selected plaintexts. The attack is based on the fact that wrap errors occur more frequently if blinding polynomials with larger coefficients are used.

Double encryption has been suggested to strengthen the Federal Data Encryption Standard (DES). A recent proposal suggests that using two 56-bit keys but enciphering 3 times (encrypt with a first key, decrypt with a second key, then encrypt with the first key again) increases security over simple double encryption. This paper shows that although either technique significantly improves security over single encryption, the new technique does not significantly increase security over simple double encryption. Cryptanalysis of the 112-bit key requires about 2 56 operations and words of memory, using a chosen plaintext attack. While DES is used as an example, the technique is applicable to any similar cipher.

The Rao-Nam scheme is discussed and generalized to Fq. It is shown that the scheme is insecure against a chosen-plaintext attack for practical code lengths. Based on observations an improved scheme is given, which is not vulnerable to the chosen-plaintext attacks as described.

In present time, in order to provide security of multimedia data while transmission and storage processes, the protection of image data can be accomplished using encryption. This paper presents a new image encryption scheme relaying on a chaotic 3D cat map and Turing machine in the form of dynamic random growth technique. The proposed technique composed of two processes of pixels' locations confusion using a chaotic 3D cat map, which is performed concurrently with substituting values swapping pixels' locations using Turing machine. The generated key is dependent on the plain image, to resist the chosen plaintext attack. Both experimental and security analysis show that the presented technique can achieve a large key space and resist the common against cipher attacks. These good cryptographic advantages make it suitable for image transmission over network.

Securing transmission over a wireless network is especially challenging, not only because of the inherently insecure nature of the medium, but also because of the highly error-prone nature of the wireless environment. In this paper, we take a joint encryption-error correction approach to ensure secure and robust communication over the wireless link. In particular, we design an error-correcting cipher (called the high diffusion cipher) and prove bounds on its error-correcting capacity as well as its security. Towards this end, we propose a new class of error-correcting codes (HD-codes) with built-in security features that we use in the diffusion layer of the proposed cipher. We construct an example, 128-bit cipher using the HD-codes, and compare it experimentally with two traditional concatenated systems: (a) AES (Rijndael) followed by Reed-Solomon codes, (b) Rijndael followed by convolutional codes. We show that the HD-cipher is as resistant to linear and differential cryptanalysis as the Rijndael. We also show that any chosen plaintext attack that can be performed on the HD cipher can be transformed into a chosen plaintext attack on the Rijndael cipher. In terms of error correction capacity, the traditional systems using Reed-Solomon codes are comparable to the proposed joint error-correcting cipher and those that use convolutional codes require more data expansion in order to achieve similar error correction as the HD-cipher. The original contributions of this work are (1) design of a new joint error-correction-encryption system, (2) design of a new class of algebraic codes with built-in security criteria, called the high diffusion codes (HD-codes) for use in the HD-cipher, (3) mathematical properties of these codes, (4) methods for construction of the codes, (5) bounds on the error-correcting capacity of the HD-cipher, (6) mathematical derivation of the bound on resistance of HD cipher to linear and differential cryptanalysis, (7) experimental comparison of the HD-cipher with the traditional systems.