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In: Computer Science

A message has been encrypted by Bob using row transposition cipher to give the following ciphertext:...

A message has been encrypted by Bob using row transposition cipher to give the following ciphertext:

TTNA APTM TSUO AODW COIX KNLY PETZ

However when Bob shared the key with Alice, it got copied multiple times and looks like:

…. 6 7 4 3 1 2 5 6 7 4 3 1 2 5 6 7 4 3 1 2 5 6 7 4 3 1 2 5 6 7 4 3 1 2 ……

You see a series of numbers repeating. However you do not know which number

to start the key with.

  1. How many keys will you have to try to find the correct key (maximum keys you may have to try)?

  2. Find the correct key. Describe the process you followed to find the key.

  3. Decrypt the ciphertext given above and find the plaintext.

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