TheINDOCRYPTconferenceseriesstartedin2000,andINDOCRYPT2003was the fourth one in this series. This series has been accepted by the international research community as a forum for presenting high-quality crypto research, as is evident from the 101 submissions this year, spread over 21 countries and all ?ve continents. The accepted papers were written by authors from 16 countries, covering four continents. A total of 101 papers were submitted for consideration to the program c- mittee, and after a careful reviewing process 30 were accepted for presentation. One of the conditionally accepted papers was withdrawn by the authors as they found an errorin the paper that could not be repairedin the short time between the noti?cation of the reviewand the ?nalversionsubmission.Thus the ?nal list contains29acceptedpapers.Wewouldliketo thanktheauthorsofallsubmitted papers, including both those that wereaccepted and those which, unfortunately, could not be accommodated. The reviewing process for INDOCRYPT was very stringent and the schedule was extremely tight. The program committee members did an excellent job in reviewing and selecting the papers for presentation. During the review process, theprogramcommitteememberscommunicatedusingareviewsoftwarepackage developed by Bart Preneel, Wim Moreau and Joris Claessens. We acknowledge them for providing this software. These proceedings include the revised versions of the 29 selected papers. Revisions were not checkedby the programcommittee and the authors bear the full responsibility for the contents of the respective papers. Our thanks go to all the program committee members and the external reviewers(alistofthem isincludedintheproceedings)whoputintheirvaluable time and e?ort in providing important feedback to the authors.

Includes supplementary material: sn.pub/extras

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Invited Talks.- Linear Complexity and Related Complexity Measures for Sequences.- Forensic Computing.- Stream Cipher.- Hiji-bij-bij: A New Stream Cipher with a Self-synchronizing Mode of Operation.- Analysis of Non-fortuitous Predictive States of the RC4 Keystream Generator.- Block Cipher.- Nonlinearity Properties of the Mixing Operations of the Block Cipher IDEA.- Impossible Differential Cryptanalysis for Block Cipher Structures.- Impossible Differential Attack on 30-Round SHACAL-2.- Boolean Function.- Construction of Perfect Nonlinear and Maximally Nonlinear Multi-output Boolean Functions Satisfying Higher Order Strict Avalanche Criteria.- Improved Cost Function in the Design of Boolean Functions Satisfying Multiple Criteria.- Secrect Sharing.- On Multiplicative Linear Secret Sharing Schemes.- A New (2,n)-Visual Threshold Scheme for Color Images.- On the Power of Computational Secret Sharing.- Bilinear Pairing.- Identity-Based Broadcasting.- Efficient Verifiably Encrypted Signature and Partially Blind Signature from Bilinear Pairings.- Extending Joux's Protocol to Multi Party Key Agreement.- Public Key.- Public Key Cryptosystems Based on Free Partially Commutative Monoids and Groups.- Prime Numbers of Diffie-Hellman Groups for IKE-MODP.- Polynomial Equivalence Problems and Applications to Multivariate Cryptosystems.- Signature Scheme.- Security Analysis of Several Group Signature Schemes.- Forking Lemmas for Ring Signature Schemes.- Protocol.- Practical Mental Poker Without a TTP Based on Homomorphic Encryption.- Lightweight Mobile Credit-Card Payment Protocol.- Elliptic Curve & Algebraic Geometry.- On the Construction of Prime Order Elliptic Curves.- Counting Points on an Abelian Variety over a Finite Field.- Implementation & Digital Watermarking.- Side ChannelAttack on Ha-Moon's Countermeasure of Randomized Signed Scalar Multiplication.- Systolic and Scalable Architectures for Digit-Serial Multiplication in Fields GF(p m ).- Cryptanalysis of Block Based Spatial Domain Watermarking Schemes.- Authentication.- More Efficient Password Authenticated Key Exchange Based on RSA.- A Password-Based Authenticator: Security Proof and Applications.- Stronger Security Bounds for OMAC, TMAC, and XCBC.- Progressive Verification: The Case of Message Authentication.