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# CS205 Information Security Assignment #2- Fall 2018- Due Date: 18 January

Scenario

Suppose we have encrypted a plaintext using transportation block cipher method. We have used three keys K1, K2 and K3 which are of 8, 16 and 8 bits respectively and having followed key pattern:

Key Patterns

Key Pattern 1 (K1)

1↦2, 2↦8, 3↦5, 4↦7, 5↦3, 6↦4, 7↦1, 8↦6

Key Pattern 2 (K2)

1↦3, 2↦10, 3↦8, 4↦12, 5↦7, 6↦13, 7↦2, 8↦16, 9↦15, 10↦11, 11↦5, 12↦14, 13↦1, 14↦6, 15↦9, 16↦4

Key Pattern 3 (K3)

1↦4, 2↦7, 3↦3, 4↦1, 5↦8, 6↦2, 7↦5, 8↦6

First, you should have encrypted their plain text using Key K1, then the result (obtained cipher text through K2 encryption) is encrypted again by Key K2 and at the end we have Encrypted the Ciphertext again using K3.

Final Cipher Text

chwIuin jnayse“t  triaeh eraste cyroui  jveesett-nihe eMrrat. w”K.rLh unt gJei r

Question Statement

You have to convert Final Cipher Text back to Plain Text by decrypting it using Keys.

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### Replies to This Discussion

I have done the decryption i am just not sure wether its the desired result. if you have done it too lets discuss it here. lets see if we have the same result :)

exert your own effort.... If u want to make yourself real student.

been doing that for 3 days. its a pretty tough task. one mistake and the whole things goes wrong. :/

if you have done it . will you please send my right now.

i am also trying my best to find out the decryption process.

you have to inlude all spaces and other characters too then you will find it

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