cryptography Cryptography, or cryptology (from "hidden, secret"; and ''graphein'', "to write", or ''-logy, -logia'', "study", respectively), is the practice and study of techniques for secure communication in the presence of Adversary (cryptography), ...

, MISTY1 (or MISTY-1) is a

block cipher 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 a ...

designed in 1995 by

Mitsuru Matsui is a Japanese cryptographer and senior researcher for Mitsubishi Electric Company. Career While researching error-correcting codes in 1990, Matsui was inspired by Eli Biham and Adi Shamir's differential cryptanalysis, and discovered the techniqu ...

and others for

Mitsubishi Electric is a Japanese Multinational corporation, multinational electronics and electrical equipment manufacturing company headquartered in Tokyo, Japan. The company was established in 1921 as a spin-off from the electrical machinery manufacturing d ...

. MISTY1 is one of the selected algorithms in the

Europe Europe is a continent located entirely in the Northern Hemisphere and mostly in the Eastern Hemisphere. It is bordered by the Arctic Ocean to the north, the Atlantic Ocean to the west, the Mediterranean Sea to the south, and Asia to the east ...

NESSIE NESSIE (New European Schemes for Signatures, Integrity and Encryption) was a European research project funded from 2000 to 2003 to identify secure cryptographic primitives. The project was comparable to the NIST AES process and the Japanese Go ...

project, and has been among the cryptographic techniques recommended for Japanese government use by

CRYPTREC CRYPTREC is the Cryptography Research and Evaluation Committees set up by the Japanese Government to evaluate and recommend cryptographic techniques for government and industrial use. It is comparable in many respects to the European Union's NESSI ...

in 2003; however, it was dropped to "candidate" by CRYPTREC revision in 2013. However, it was successfully broken in 2015 by Yosuke Todo using

integral cryptanalysis In cryptography, integral cryptanalysis is a cryptanalytic attack that is particularly applicable to block ciphers based on substitution–permutation networks. It was originally designed by Lars Knudsen as a dedicated attack against Square, so ...

; this attack was improved in the same year by Achiya Bar-On. "MISTY" can stand for "Mitsubishi Improved Security Technology"; it is also the initials of the researchers involved in its development: Matsui Mitsuru, Ichikawa Tetsuya, Sorimachi Toru, Tokita Toshio, and Yamagishi Atsuhiro. MISTY1 is covered by patents, although the algorithm is freely available for academic (non-profit) use in RFC 2994, and there's a GPLed implementation by Hironobu Suzuki (used by, e.g.

Scramdisk ''Scramdisk'' is a free on-the-fly encryption program for Windows 95, Windows 98, and Windows Me. A non-free version was also available for Windows NT. The original ''Scramdisk'' is no longer maintained; its author, Shaun Hollingworth, joined Pa ...

Security

MISTY1 is a

Feistel network In cryptography, a Feistel cipher (also known as Luby–Rackoff block cipher) is a symmetric structure used in the construction of block ciphers, named after the German-born physicist and cryptographer Horst Feistel, who did pioneering researc ...

with a variable number of rounds (any multiple of 4), though 8 are recommended. The cipher operates on 64-bit blocks and has a

key size In cryptography, key size or key length refers to the number of bits in a key used by a cryptographic algorithm (such as a cipher). Key length defines the upper-bound on an algorithm's security (i.e. a logarithmic measure of the fastest known a ...

of 128 bits. MISTY1 has an innovative recursive structure; the round function itself uses a 3-round Feistel network. MISTY1 claims to be provably secure against

linear In mathematics, the term ''linear'' is used in two distinct senses for two different properties: * linearity of a '' function'' (or '' mapping''); * linearity of a '' polynomial''. An example of a linear function is the function defined by f(x) ...

and

differential cryptanalysis Differential cryptanalysis is a general form of cryptanalysis applicable primarily to block ciphers, but also to stream ciphers and cryptographic hash functions. In the broadest sense, it is the study of how differences in information input can a ...

KASUMI

KASUMI is a successor of the MISTY1 cipher which was supposed to be stronger than MISTY1 and has been adopted as the standard encryption algorithm for European

mobile phone A mobile phone or cell phone is a portable telephone that allows users to make and receive calls over a radio frequency link while moving within a designated telephone service area, unlike fixed-location phones ( landline phones). This rad ...

s. In 2005, KASUMI was broken, and in 2010 a new paper was published (explained below) detailing a practical attack on the cipher; see the article for more details. In the paper "Block Ciphers and Stream Ciphers" by

Alex Biryukov Alex Biryukov () is a cryptographer, currently a full professor at the University of Luxembourg. Biography His notable work includes the design of the stream cipher LEX, as well as the cryptanalysis of numerous cryptographic primitives. In 1998, ...

, it is noted that KASUMI, also termed A5/3, is a strengthened version of block cipher MISTY1 running in a Counter mode. However, in 2010 Dunkelman, Keller, and Shamir showed that KASUMI is not as strong as MISTY1; the KASUMI attack will not work against MISTY1.

References

External links

*
Mitsubishi - About MISTY

MISTY1 patent statement from Mitsubishi

{{Mitsubishi Electric Feistel ciphers Mitsubishi Electric products, services and standards