Sean Murphy

I am a Professor in the School of Mathematics and Information Security at Royal Holloway (University of London). Please note that I do not supervise internships.

Books

  • Carlos Cid, Sean Murphy and Matthew Robshaw, Algebraic Aspects of the Advanced Encryption Standard, Springer, ISBN 0-387-24363-1, 2006.

  • Fred Piper and Sean Murphy, Cryptography: a Very Short Introduction, Oxford University Press, ISBN 0-19-280315-8, 2002.

    Research

    My academic research concentrates on mathematical cryptology. I was a leader of the NESSIE project, a European project to assess cryptographic primitives for future possible standardisation. I was also a member of the committee which set up ECRYPT project, a European Network of Excellence in Cryptology consiting of 35 European organisations working in cryptology. Some of my publications are listed below. Please note that the copyright usually belongs to the relevant publisher.

    Stochastic and Statistical Issues in Cryptology

  • R. Bricout, S. Murphy, K.G. Paterson, and T. van der Merwe, Analysing and Exploiting the Mantin Biases in RC4, Designs, Codes and Cryptography, Vol. 84, pp743-770, 2018.

  • S. Murphy and R. Player, Noise Distributions in Ring-LWE, preliminary version available as IACR eprint 2017/698, 2017.

  • S.D. Galbraith, S.W. Gebregiyorgis and S. Murphy, Algorithms for the Approximate Common Divisor Problem, London Mathematical Society Journal of Mathematical Computation (Algebraic Number Theory Symposium XII), Vol. 19(A), pp58-72, 2016. A longer version is available as IACR eprint 2016/215.

  • S. Murphy, Mean Squared Length of Vectors in the Approximate Greatest Common Divisor Lattice. Please note that this version (September 2012) corrects a minor typo in the previous version (May 2012). A version is available as Departmental Technical Report RHUL-MA-2012-06.

  • S. Murphy, The Effectiveness of the Linear Hull Effect, Journal of Mathematical Cryptology, Vol. 6, pp137-148, 2012. Linear Hull Addendum, March 2015.

  • S. Murphy, The Analysis of Simultaneous Differences in Differential Cryptanalysis. A version is available as Departmental Technical Report RHUL-MA-2012-13.

  • S. Murphy, Overestimates for the Gain of Multiple Linear Approximations. IEEE Transactions on Information Theory, Vol. 57, pp4794-4797, 2011.

  • S. Murphy, The Return of the Cryptographic Boomerang. IEEE Transactions on Information Theory, Vol. 57, pp2517-2521, 2011.

  • S.Murphy, The Independence of Linear Approximations in Symmetric Cryptology, IEEE Transactions on Information Theory, Vol. 52, pp5510-5518, 2006.

  • S.Murphy and M.Robshaw, Differential Cryptanalysis, Key-Dependent S-Boxes and Twofish, Designs, Codes and Cryptography, Vol. 27, pp229-255, 2002.

  • S.Murphy, The Power of NISTs Statistical Testing of AES Candidates, AES Comment to NIST, April 2000.

  • D. Erdmann and S. Murphy, An Approximate Distribution for the Maximum Order Complexity Designs, Codes and Cryptography, Vol. 10, pp. 325-329, 1997.

  • S. Murphy, F.Piper, M.Walker and P.Wild, Maximum Likelihood Estimation for Block Cipher Keys Research Report 1995 (Similar versions 1992 and 1994). Available as Departmental Technical Report RHUL-MA-2006-3.

  • D. Davies and S. Murphy, Pairs and Triplets of DES S-Boxes J. Cryptology, Vol. 8, pp. 1-25, 1995.

  • X. Lai, J. Massey and S. Murphy, Markov Ciphers and Differential Cryptanalysis in Advances in Cryptology -- EUROCRYPT 91 , LNCS 547,, pp. 17-38, 1991.

    Algebraic Techniques in Cryptology

    I am interested in the use of algebraic techniques in symmetric cryptology, particularly the analysis of the (National Institute of Standards and Technology) Advanced Encryption Standard (AES), and I was Principal Investigator of the Engineering and Physical Sciences Research Council (EPSRC) project Security Analysis of the Advanced Encryption Standard.

  • S. Murphy and M.B. Paterson, Geometric Ideas for Cryptographic Equation Solving in Even Characteristic, Proceedings of the 12th IMA International Conference on Coding and Cryptography, LNCS 5921, pages 202-221, 2009.

  • S. Murphy and M.B. Paterson, A Geometric View of Cryptographic Equation Solving, Journal of Mathematical Cryptology, Vol. 2, pages 63-107, 2008. A version is available as Departmental Technical Report RHUL-MA-2007-4.

  • Wen-Ai Jackson and S. Murphy, Projective Aspects of the AES Inversion, Designs, Codes and Cryptography, Vol. 43, pages 167-179, 2007. A version is available as Departmental Technical Report RHUL-MA-2006-4.

  • C.Cid, S.Murphy and M.Robshaw, An Algebraic Framework for Cipher Embeddings, Proceedings of the 10th IMA International Conference on Coding and Cryptography, LNCS 3796, pages 278-289, 2005.

  • C.Cid, S.Murphy and M.Robshaw, Small Scale Variants of the AES , Fast Software Encryption - FSE2005, LNCS 3557, pages 145-162, 2005.

  • C.Cid, S.Murphy and M.Robshaw, Computational and Algebraic Aspects of the Advanced Encryption Standard, Seventh International Workshop on Computer Algebra in Scientific Computing, CASC 2004, pp. 93-103, St. Petersburg, Russia, 2004.

  • S.Murphy and M.Robshaw, Comments on the Security of the AES and the XSL Technique, Electronic Letters, Vol. 39, pages 36-38, 2003.

  • S.Murphy and M.Robshaw, Essential Algebraic Structure within the AES, Advances in Cryptology -- CRYPTO 2002, Lecture Notes in Computer Science 2442, M. Yung (Ed.) (Springer, Berlin, 2002), pp. 1-16. Errata and the matrices M and M* are available.

  • S.Murphy and M.Robshaw. New Observations on Rijndael, AES Comment to NIST, August 2000. This is a note on the linear diffusion layer in Rijndael. The designers response: Answer to New Observations on Rijndael, AES Comment to NIST, August 2000. A further note concerning the linear diffusion layer of Rijndael: Further Comments on the Structure of Rijndael, AES Comment to NIST, August 2000.

    NESSIE Reports

    The NESSIE project was an EU project (2000-03) to assess cryptographic algorithms for possible standardisation.

  • B.Breneel et al, The NESSIE Book, April 2004.

  • B.Breneel et al, NESSIE Security Report, April 2003.

  • S.Murphy and J.White (editors), Security Evaluation of NESSIE First Phase, September 2001.

  • S.Murphy (Editor), Comments by the NESSIE Project on the AES Finalists, AES Comment to NIST, May 2000.

    Other Cryptology Publications

  • S.Murphy, The Key Separation of Twofish, AES Comment to NIST, April 2000.

  • F.Mirza and S. Murphy, An Observation on the Key Schedule of Twofish, NIST 2nd AES Conference, Rome, Italy, March 1999.

  • S. Murphy, An Analysis of SAFER, J. Cryptology. Vol. 11, pp235--251, 1998.

  • S.R.Blackburn and S. Murphy, The Number of Partitions in Pollard Rho, 1998. Available as Departmental Technical Report RHUL-MA-2011-11.

  • S.R.Blackburn, K. Brincat, F. Mirza and S. Murphy, Cryptanalysis of Labyrinth stream cipher, Electronics Letters, Vol. 34, pp. 1220-1221, 1998.

  • S. Murphy, Comment on "Bound for linear complexity of BBS sequences" Electronics Letters, Vol. 34, pp. 1057-1058, 1998.

  • S.R.Blackburn, S. Murphy and K.G. Paterson, A Comment on "A New Public-Key Cipher System Based Upon Diophantine Equations" , IEEE Trans. Comp., Vol. 46, pp. 512, 1997.

  • S.R.Blackburn, S. Murphy and K.G. Paterson, Comments on "Theory and Applications of Cellular Automata to Cryptography" , IEEE Trans. Comp., Vol. 46, pp. 637-638, 1997.

  • S.R.Blackburn, G. Carter, D. Gollmann, S. Murphy, K.Paterson, F.Piper, and P. Wild, Aspects of Linear Complexity, in Communications and Cryptography, (Blahut, Costello, Maurer, Mittelholzer eds) pp. 35-42, Kluwer, 1994.

  • S.R.Blackburn, S. Murphy and J. Stern, The Cryptanalysis of a Public Key Implementation of Finite Group Mappings J. Cryptology, Vol. 8, pp. 157-166, 1995.

  • S. Murphy, K.Paterson and P. Wild, A Weak Cipher that generates the Symmetric Group J. Cryptology, Vol. 7, pp. 61-65, 1994.

  • S.R.Blackburn, S. Murphy and J. Stern, Weaknesses of a Public-Key Cryptosystem based on Factorizations of Finite Groups in Advances in Cryptology -- EUROCRYPT 93, LNCS 765, pp. 50-54, 1994. Note that this paper is similar to the Journal of Cryptology 1995 paper above.

  • S. Murphy, Remarks on the LUC public key system Electronics Letters, Vol. 30, pp. 558-559, 1994.

  • D. Erdmann and S. Murphy, The Henon Stream Cipher Electronics Letters, Vol. 28, pp. 893-895, 1992.

  • S. Murphy, The Cryptanalysis of FEAL-4 using 20 chosen plaintexts J. Cryptology, Vol. 2, pp. 145-154, 1990.

    Sean Murphy

    Professor Sean Murphy,
    School of Mathematics and Information Security,
    Royal Holloway, University of London,
    Egham, Surrey TW20 0EX, U.K.
    Phone: +44 (0)1784 443699
    Fax : +44 (0)1784 430766
    Email: s.murphy@rhul.ac.uk