Dragon is a

stream cipher 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 ...

developed at the

Information Security Institute Johns Hopkins University (Johns Hopkins, Hopkins, or JHU) is a private university, private research university in Baltimore, Maryland. Founded in 1876, Johns Hopkins is the oldest research university in the United States and in the western hem ...

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 eSTREAM is a project to "identify new stream ciphers suitable for widespread adoption", organised by the EU ECRYPT network. It was set up as a result of the failure of all six stream ciphers submitted to the NESSIE project. The call for primiti ...

project, and satisfied all the requirements for speed and security. The cipher is targeted for fast

software Software is a set of computer programs and associated documentation and data. This is in contrast to hardware, from which the system is built and which actually performs the work. At the lowest programming level, executable code consists ...

implementations and versions with different

key Key or The Key may refer to: Common meanings * Key (cryptography), a piece of information that controls the operation of a cryptography algorithm * Key (lock), device used to control access to places or facilities restricted by a lock * Key (map ...

lengths exists. The version selected for Phase 3 is Dragon-128. It is not

Patent A patent is a type of intellectual property that gives its owner the legal right to exclude others from making, using, or selling an invention for a limited period of time in exchange for publishing an enabling disclosure of the invention."A p ...

ed. Dragon has not been successfully attacked to date, but Cho and Pieprzyk found biases within the primary non-linear component of the cipher.http://www.ecrypt.eu.org/stream/papersdir/2007/002.pdf 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.

External links

eSTREAM page on Dragon

Notes

Stream ciphers {{crypto-stub