On "Secured" Encryption Schemes.

Date of Submission

December 2001

Date of Award

Winter 12-12-2002

Institute Name (Publisher)

Indian Statistical Institute

Document Type

Master's Dissertation

Degree Name

Master of Technology

Subject Name

Computer Science


Applied Statistics Unit (ASU-Kolkata)


Roy, Bimal Kumar (ASU-Kolkata; ISI)

Abstract (Summary of the Work)

Data encryption (cryptography) is utilized in various applications and environments. In general, cryp- tography is used to protect data while it is being communicated between two points or while it is stored in a medium vulnerable to physical theft. Communication security provides protection to data by enciphering it at the transmitting point and deciphering it at the receiving point. File security provides protection to data by enciphering it when it is recorded on a storage medium and deciphering it when it is read back from the storage medium. In the first case, the key must be available at the transmitter and receiver simultaneously during communication. In the second case, the key must be maintained and accessible for the duration of the storage period.The most well-known symmetric eneryption algorithm is the Data Encryption Standard (DES). It defines a block cipher with 64-bit blocks and 56-bit keys. Because of its small key size exhaustion of the .DES (i.e., breaking a DES encrypted ciphertext by trying all possible keys) has become increasingly more feasible with technology advances. Following a recent hardware based DES key exhaustion attack, National Institute of Standards and Technology (NIST) (13] no onger supports the use of single DES for many applications and suggested the use of triple DES (i.e. applying single DES 3 times). Triple DES is currently the most widely used encryption standard. In 1997, NIST initiated a process to select a symmetric-key encryption algorithm, to be called Advanced Encryption Standard (AES), which is atleast as secure as triple DES and capable of protecting sensitive government information well into the twenty-first century. NIST expects that the algorithm will be used by the U.S. Government and, on a voluntary basis, by the private sector.The organization of this report is as follows: In section 2 we review DES, triple DES and their cryptanalysis. In section 3 we sketch the development process for the AES and a brief overview of the five finalists of AES. In section 4 we discuss the proposed AES (Rijndael) and a software implementation by Dr.Brian Gladman (7). In the section 5 we briefly discurs the main features of Encryption Modes with Almost Free Message Integrity for AES suggested by Charanjit S. Jutla (11] and our implementation of that mode for AES. The mode has two variations 1) Integrity Aware Cipher Block Chaining Mode (IACBC) and 2) Integrity Aware Parallekzable Mode (IAPM). The Appendix contains the C implementation of IAPM. Minor changes are required in this code to implement LACBC.


ProQuest Collection ID: http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqm&rft_dat=xri:pqdiss:28843325

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Creative Commons License

Creative Commons Attribution 4.0 International License
This work is licensed under a Creative Commons Attribution 4.0 International License.



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