Turing (cipher)

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Turing is a stream cipher developed by Gregory G. Rose and Philip Hawkes at Qualcomm for CDMA.Gregory G. Rose and Philip Hawkes, Turing: A Fast Stream Cipher, Fast Software Encryption 2003, pp. 290–306 [https://web.archive.org/web/20040708144423/http://www.qualcomm.com.au/PublicationsDocs/Turing.pdf (PDF)].

Turing generates 160 bits of output in each round by applying a non-linear filter to the internal state of an LFSR. It is named after Alan Turing. It was developed based on the SOBER cipher introduced by Rose in 1998.{{Cite book|title=New Stream Cipher Designs: The ESTREAM Finalists|last=Robshaw|first=Matthew|last2=Billet|first2=Olivier|date=2008|publisher=Springer Science & Business Media|isbn=978-3540683506|location=Berlin|pages=58}} This is evident in its major component, the Linear Feedback Shift Register (LFSR), which is the same technology found in the family of SOBER machines.{{Cite book|title=Fast Software Encryption: 10th International Workshop, FSE 2003, LUND, Sweden, February 24-26, 2003, Revised Papers|last=Johansson|first=Thomas|date=2003|publisher=Springer Science & Business Media|isbn=3540204490|location=Berlin|pages=290}} Turing, however, is distinguished from its predecessors by the way it produces five words (five times more) of output for every internal update. It also provides up to 256-bit key strength and is designed to be fast in software, achieving around 5.5 cycles/byte on some x86 processors.

There are experts who found that the Turing stream cipher has a number of weaknesses when faced with chosen IV attacks.{{Cite book|title=Selected Areas in Cryptography: 10th Annual International Workshop, SAC 2003, Ottawa, Canada, August 14-15, 2003, Revised Papers|last=Matsui|first=Mitsuru|last2=Zuccherato|first2=Robert|date=2004|publisher=Springer Science & Business Media|isbn=3540213708|location=Berlin|pages=205}} For instance, its key scheduling algorithm has the same secret key for different initialization vectors and this is found to lower the system's security.