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Encryption for Mobile Computing

Encryption for Mobile Computing. By Erik Olson Woojin Yu. Encryption Algorithms. DES and 3DES RC5 RC6 – AES Finalist Twofish- AES Finalist. DES and 3DES. DES - International Standard, 1970’s 3DES – repeated encryption with DES

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Encryption for Mobile Computing

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  1. Encryption for Mobile Computing By Erik Olson Woojin Yu

  2. Encryption Algorithms • DES and 3DES • RC5 • RC6 – AES Finalist • Twofish- AES Finalist

  3. DES and 3DES • DES - International Standard, 1970’s • 3DES – repeated encryption with DES • Extensive usage of permutation, table look-ups, and rotational shifts • 56 bit key – weak encryption

  4. RC5 • Fast block cipher • By Ron Rivest at RSA in 1994 • Based on integer addition, data dependent rotational shifts and XOR’s • Very simple, but powerful • Patented

  5. RC6 • Based on RC5 algorithm • One finalist for AES • 128 bit blocks for AES • Flexible

  6. Twofish • AES finalist • XOR’s, 32 bit and 4 bit rotational shifts, table lookups, and matrix operations • Scalable and parameterizable • Some operations can be done in parallel

  7. Processor in Our Survey • Motorola DragonBall EZ - 68K core - Primarily used in Palm Pilots - 16.58 Mhz - 2.7 MIPS rating

  8. Setup and Makekey • Shifts and Rotational Shifts • A=A>>8 • ROTL(x,n)= (x<<(n & 0x1f))|(x >> 0x20-(n&0x1f)) • Word Swapping • A->B, B->A • Extensive usage of loops • Array operations • S[I]=S[I-1]+4

  9. 3DES Setup

  10. RC5 Setup

  11. RC6 Setup

  12. Twofish Setup

  13. Core Operations • Rotational Shifts • ROTL(x,n)= (x<<(n & 0x1f))|(x >> 0x20-(n&0x1f)) • ROTR(x,n)= (x>>(n & 0x1f))|(x << 0x20-(n&0x1f)) • XOR • A=A^B

  14. Core Op Cont’d • Integer Operations • A=A+S[0] • Bit Permutation • A=01001110 SP={5,7,1,3,2,8,4,6} A=11001001 after permutation • Using Constants • P=0xb7e15163, • A=A^P

  15. 3DES Core

  16. RC5 Core

  17. RC6 Core

  18. Twofish Core

  19. Analysis & Improvement • Using Rotational Shift instruction • Implementing special shifting unit • LSR and LSL dominate the clock cycles • Minimize Move Instruction/Penalty

  20. Analysis Cont’d • Improvement using ROT instruction • 1.5 times speed up in encryption core • Improvement using fast rotation HW • 2 times speed up in encryption core

  21. Analysis Cont’d • 3DES Core • 6.1 Kbps • RC5 Core • 121 Kbps • Improved version : 272 Kbps • RC6 Core • 87 Kbps • Improved version : 187 Kbps • Twofish • 12.8 Kbps

  22. Conclusion • Dominance of shifts and rotational shifts in all encryption algorithms • Limited improvement provided by the specialized hardware • Importance of algorithm choice for optimal usage

  23. Future Recommendations • Analysis on Windows CE processors – Hitachi SH3 and StrongArm • Analysis involving more instruction parallelism • Analysis on configurable processors - Tensilica

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