Simplified IDEA Cryptography and Network Security.

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Presentation transcript:

Simplified IDEA Cryptography and Network Security

Components of IDEA Key generation Three operations Multiple rounds and an output transformation

IDEA Simplified IDEA 128-bit key 64-bit plaintext 8 rounds 8*6 + 4 = 52 16-bit subkeys 64-bit plaintext 8 rounds Operations: modulo 216 and 216+1 16-bit key 2*6 + 4 = 16 2-bit subkeys 8-bit plaintext 2 rounds Operations: modulo 22 and 22+1

Key Generation 16-bit key: Z[1..16] Z1 = Z[1,2] , Z2 = Z[3,4], …, Z8 = Z[15,16] Z9 = Z[4,5], Z10 = Z[5,6], …, Z13 = Z[12,13], Z14 = Z[14,15] Z15 = Z[16,1], Z16= Z[2,3] (rotate 3 bits to the left before extracting second set of 8 subkeys)

Two-bit Operands Plaintext divided into 4 2-bit pieces and subjected to the two round and final output transformation 2-bit subkeys used as follows: Z1..Z6 for first round Z7..Z12 for second round Z13..Z16 for final transformation

Operations XOR Addition modulo 4 Multiplication modulo 5

Encryption Decryption Subkeys Subkeys Z1, Z2, Z3, Z4, Z5, Z6 Z7, Z8, Z9, Z10, Z11, Z12 Z13, Z14, Z15, Z16 Z13-1, -Z14, -Z15 Z16-1, Z11, Z12 Z7-1, -Z9, -Z8, Z10-1, Z5, Z6 Z1-1, -Z2, -Z3, Z4-1