Cipher

About: Cipher is a research topic. Over the lifetime, 9409 publications have been published within this topic receiving 110309 citations. The topic is also known as: cypher & cryptographic algorithm.

Infective computation and dummy rounds: fault protection for block ciphers without check-before-output

Abstract: Implementation attacks pose a serious threat for the security of cryptographic devices and there are a multitude of countermeasures that are used to prevent them. Two countermeasures used in implementations of block ciphers to increase the complexity of such attacks are the use of dummy rounds and redundant computation with consistency checks to prevent fault attacks. In this paper we present several countermeasures based on the idea of infective computation. Our countermeasures ensure that a fault injected into a cipher, dummy, or redundant round will infect the ciphertext such that an attacker cannot derive any information on the secret key being used. This has one clear advantage: the propagation of faults prevents an attacker from being able to conduct any fault analysis on any corrupted ciphertexts. As a consequence, there is no need for any test at the end of an implementation to determine if a fault has been injected and a ciphertext can always be returned.

Secure presentation of media streams in response to encrypted digital content

Abstract: Secure presentation of media streams includes encoding the media streams into digital content, encrypting a portion of that digital content, the portion being required for presentation, in which the encrypted version is substantially unchanged in formatting parameters from the clear version of the digital content. Selecting those portions for encryption so there is no change in distribution of the media stream: packetization of the digital data, or synchronization of audio with video portions of the media stream. When encoding the media stream into MPEG-2, refraining from encrypting information by which the video block data is described, packet formatting information, and encrypting the video block data using a block-substitution cipher. A block-substitution cipher can be used to encrypt each sequence of 16 bytes of video data in each packet, possibly leaving as many as 15 bytes of video data in each packet in the clear.

Sieve-in-the-Middle: Improved MITM Attacks

Abstract: This paper presents a new generic technique, named sieve-in-the-middle, which improves meet-in-the-middle attacks in the sense that it provides an attack on a higher number of rounds. Instead of selecting the key candidates by searching for a collision in an intermediate state which can be computed forwards and backwards, we look for the existence of valid transitions through some middle sbox. Combining this technique with short bicliques allows to freely add one or two more rounds with the same time complexity. Moreover, when the key size of the cipher is larger than its block size, we show how to build the bicliques by an improved technique which does not require any additional data (on the contrary to previous biclique attacks). These techniques apply to PRESENT, DES, PRINCE and AES, improving the previously known results on these four ciphers. In particular, our attack on PRINCE applies to 8 rounds (out of 12), instead of 6 in the previous cryptanalyses. Some results are also given for theoretically estimating the sieving probability provided by some inputs and outputs of a given sbox.

Bi-level Protected Compressive Sampling

Abstract: Some pioneering works have investigated embedding cryptographic properties in compressive sampling (CS) in a way similar to one-time pad symmetric cipher. This paper tackles the problem of constructing a CS-based symmetric cipher under the key reuse circumstance, i.e., the cipher is resistant to common attacks even a fixed measurement matrix is used multiple times. To this end, we suggest a bi-level protected CS (BLP-CS) model which makes use of the advantage of the non-RIP measurement matrix construction. Specifically, two kinds of artificial basis mismatch techniques are investigated to construct key-related sparsifying bases. It is demonstrated that the encoding process of BLP-CS is simply a random linear projection, which is the same as the basic CS model. However, decoding the linear measurements requires knowledge of both the key-dependent sensing matrix and its sparsifying basis. The proposed model is exemplified by sampling images as a joint data acquisition and protection layer for resource-limited wireless sensors. Simulation results and numerical analyses have justified that the new model can be applied in circumstances where the measurement matrix can be re-used.

Cube Attacks on Non-Blackbox Polynomials Based on Division Property.

Abstract: The cube attack is a powerful cryptanalytic technique and is especially powerful against stream ciphers. Since we need to analyze the complicated structure of a stream cipher in the cube attack, the cube attack basically analyzes it by regarding it as a blackbox. Therefore, the cube attack is an experimental attack, and we cannot evaluate the security when the size of cube exceeds an experimental range, e.g., 40. In this paper, we propose cube attacks on non-blackbox polynomials. Our attacks are developed by using the division property, which is recently applied to various block ciphers. The clear advantage is that we can exploit large cube sizes because it never regards the cipher as a blackbox. We apply the new cube attack to Trivium , Grain128a, ACORN and Kreyvium. As a result, the secret keys of 832-round Trivium , 183-round Grain128a, 704-round ACORN and 872-round Kreyvium are recovered. These attacks are the current best key-recovery attack against these ciphers.