Handout 5 - DES Substitution and Permutation

# Handout 5 - DES Substitution and Permutation -...

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CIS 3360 Security in Computing Spring 2010 Handout for Permutation and Substitution Permutation A permutation is defined as any ordering of the input bits. Example 1: If a 16-bit permutation is defined as follows:

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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 14 10 6 2 16 12 8 4 13 9 5 1 15 11 7 3 Then, permute the input 1010 0011 1001 0101 Solution:
1 0 1 0 0 0 1 1 1 0 0 1 0 1 0 1 1 0 0 0 1 1 1 0 0 1 0 1 0 0 1 1 Example 2: If a 16-bit permutation is defined as follows:

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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 2 4 1 3 6 8 5 7 10 12 9 11 14 16 13 15 Then, permute the input 1010 0011 1001 0101 Solution:
1 0 1 0 0 0 1 1 1 0 0 1 0 1 0 1 0 0 1 1 0 1 0 1 0 1 1 0 1 1 0 0 Example 3: If a 16-bit permutation is defined as follows:

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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 2 6 10 14 4 8 12 16 1 5 9 13 3 7 11 15 Then, permute the input 1010 0011 1001 0101 Solution:
1 0 1 0 0 0 1 1 1 0 0 1 0 1 0 1 0 0 0 1 0 1 1 1 1 0 1 0 1 1 0 0 Example 4: If a16-bit permutation is defined as follows:

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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 4 1 2 3 8 5 6 7 12 9 10 11 16 13 14 15 Then, permute the input 1010 0011 1001 0101 Solution:
1 0 1 0 0 0 1 1 1 0 0 1 0 1 0 1 0 1 0 1 1 0 0 1 1 1 0 0 1 0 1 0

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Example 5:  Given the following 26-bit permutation, find the Caesar cipher equation that has been  used.
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

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2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 0 1

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## This note was uploaded on 10/05/2010 for the course CIS CIS 3360 taught by Professor Guha during the Spring '10 term at University of Central Florida.

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Handout 5 - DES Substitution and Permutation -...

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