Dragon is a stream cipher developed at the Information Security Institute by William Millan with some help from Ed Dawson, Kevin Chen, Matt Henricksen, Leonie Simpson, HoonJae Lee, and SangJae Moon.
Dragon is the first published stream cipher to employ a nonlinear feedback for the state update function and a nonlinear function for output, where the long minimum cycle is guaranteed by a clock-like structure. The feedback and output are generated together by a permutation that takes as input data from state words according to a full-positive difference set. These design choices make it difficult to employ standard analysis methods. The permutation uses S-boxes designed using evolutionary search heuristics.
The cipher was a Phase 3 Focus candidate for the eSTREAM project, and satisfied all the requirements for speed and security. The cipher is targeted for fast software implementations and versions with different key lengths exists. The version selected for Phase 3 is Dragon-128. It is not Patented.
Dragon has not been successfully attacked to date, but Cho and Pieprzyk found biases within the primary non-linear component of the cipher.[1] Some have suggested that the security of the cipher is weaker than intended by its designers. However, the methods to detect the biases require such a large amount of data, which would not be generated by any actual use of the algorithm, that an alternative interpretation exists: the published analysis shows that the cipher is quite secure.
In cryptography, a block cipher is a deterministic algorithm that operates on fixed-length groups of bits, called blocks. Block ciphers are the elementary building blocks of many cryptographic protocols. They are ubiquitous in the storage and exchange of data, where such data is secured and authenticated via encryption.
In cryptography, RC4 is a stream cipher. While it is remarkable for its simplicity and speed in software, multiple vulnerabilities have been discovered in RC4, rendering it insecure. It is especially vulnerable when the beginning of the output keystream is not discarded, or when nonrandom or related keys are used. Particularly problematic uses of RC4 have led to very insecure protocols such as WEP.
A stream cipher is a symmetric key cipher where plaintext digits are combined with a pseudorandom cipher digit stream (keystream). In a stream cipher, each plaintext digit is encrypted one at a time with the corresponding digit of the keystream, to give a digit of the ciphertext stream. Since encryption of each digit is dependent on the current state of the cipher, it is also known as state cipher. In practice, a digit is typically a bit and the combining operation is an exclusive-or (XOR).
In computing, a linear-feedback shift register (LFSR) is a shift register whose input bit is a linear function of its previous state.
In cryptography, linear cryptanalysis is a general form of cryptanalysis based on finding affine approximations to the action of a cipher. Attacks have been developed for block ciphers and stream ciphers. Linear cryptanalysis is one of the two most widely used attacks on block ciphers; the other being differential cryptanalysis.
In cryptography, a block cipher mode of operation is an algorithm that uses a block cipher to provide information security such as confidentiality or authenticity. A block cipher by itself is only suitable for the secure cryptographic transformation of one fixed-length group of bits called a block. A mode of operation describes how to repeatedly apply a cipher's single-block operation to securely transform amounts of data larger than a block.
In cryptography, an S-box (substitution-box) is a basic component of symmetric key algorithms which performs substitution. In block ciphers, they are typically used to obscure the relationship between the key and the ciphertext, thus ensuring Shannon's property of confusion. Mathematically, an S-box is a nonlinear vectorial Boolean function.
In cryptography, confusion and diffusion are two properties of the operation of a secure cipher identified by Claude Shannon in his 1945 classified report A Mathematical Theory of Cryptography. These properties, when present, work together to thwart the application of statistics and other methods of cryptanalysis.
In cryptography, MUGI is a pseudorandom number generator (PRNG) designed for use as a stream cipher. It was among the cryptographic techniques recommended for Japanese government use by CRYPTREC in 2003, however, has been dropped to "candidate" by CRYPTREC revision in 2013.
A nonlinear-feedback shift register (NLFSR) is a shift register whose input bit is a non-linear function of its previous state.
VEST (Very Efficient Substitution Transposition) ciphers are a set of families of general-purpose hardware-dedicated ciphers that support single pass authenticated encryption and can operate as collision-resistant hash functions designed by Sean O'Neil, Benjamin Gittins and Howard Landman. VEST cannot be implemented efficiently in software.
Grain is a stream cipher submitted to eSTREAM in 2004 by Martin Hell, Thomas Johansson and Willi Meier. It has been selected for the final eSTREAM portfolio for Profile 2 by the eSTREAM project. Grain is designed primarily for restricted hardware environments. It accepts an 80-bit key and a 64-bit IV. The specifications do not recommend a maximum length of output per pair. A number of potential weaknesses in the cipher have been identified and corrected in Grain 128a which is now the recommended cipher to use for hardware environments providing both 128bit security and authentication.
HC-256 is a stream cipher designed to provide bulk encryption in software at high speeds while permitting strong confidence in its security. A 128-bit variant was submitted as an eSTREAM cipher candidate and has been selected as one of the four final contestants in the software profile.
Rabbit is a high-speed stream cipher from 2003. The algorithm and source code was released in 2008 as public domain software.
In cryptography, SOBER is a family of stream ciphers initially designed by Greg Rose of QUALCOMM Australia starting in 1997. The name is a contrived acronym for Seventeen Octet Byte Enabled Register. Initially the cipher was intended as a replacement for broken ciphers in cellular telephony. The ciphers evolved, and other developers joined the project.
In cryptography, a distinguishing attack is any form of cryptanalysis on data encrypted by a cipher that allows an attacker to distinguish the encrypted data from random data. Modern symmetric-key ciphers are specifically designed to be immune to such an attack. In other words, modern encryption schemes are pseudorandom permutations and are designed to have ciphertext indistinguishability. If an algorithm is found that can distinguish the output from random faster than a brute force search, then that is considered a break of the cipher.
Crypto1 is a proprietary encryption algorithm and authentication protocol created by NXP Semiconductors for its MIFARE Classic RFID contactless smart cards launched in 1994. Such cards have been used in many notable systems, including Oyster card, CharlieCard and OV-chipkaart.
Surrogate data testing is a statistical proof by contradiction technique similar to permutation tests and parametric bootstrapping. It is used to detect non-linearity in a time series. The technique involves specifying a null hypothesis describing a linear process and then generating several surrogate data sets according to using Monte Carlo methods. A discriminating statistic is then calculated for the original time series and all the surrogate set. If the value of the statistic is significantly different for the original series than for the surrogate set, the null hypothesis is rejected and non-linearity assumed.
A time/memory/data tradeoff attack is a type of cryptographic attack where an attacker tries to achieve a situation similar to the space–time tradeoff but with the additional parameter of data, representing the amount of data available to the attacker. An attacker balances or reduces one or two of those parameters in favor of the other one or two. This type of attack is very difficult, so most of the ciphers and encryption schemes in use were not designed to resist it.
Shabal is a cryptographic hash function submitted by the France-funded research project Saphir to NIST's international competition on hash functions.
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