1. Bob wants to use DES to make a secured communication with Alice using DES key...

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1. Bob wants to use DES to make a secured communication withAlice using DES key â€˜Kbâ€™ to encrypt and decrypt data. Bob uses PKImethod to distribute the DES key to Alice. If Alice private key isâ€˜Kpaâ€™, and her public key is â€˜Kpbâ€™. Please describe the processthat Bob can send his DES key â€˜Kbâ€™ to Alice securely.
2. You receive a message that was encoded using a block encodingscheme with the encoding matrix
M=3275
Verify by computing M'Ã—M thatM'=524193
(remember to wrap around if a value is> 25.)
Decode the ciphertext message MXOSHI.

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2step 1 of 6Decode the block of letters using the BlockcipherBlock cipher The Block cipher is used to encrypt the block or group ofplaintext letters into block or group of ciphertext letter anddecrypt the group or block of ciphertext letter to block or groupof plaintext letters But it does not apply the same character foreach letter For encodingo Step 1 Apply the S mapping to the block ofplaintext It the simple substitution that is mapping The S maps thecharacters into integer numbers such as SA 1 SB 2SZ 26 The simple substitution for SMapping is shown belowo Step 2 Multiply the and it gets wrapped around that is usemodulo 26 to get the remainder value if any value in the matrix ismore than 25o Step 3 Apply to the result of encoding For decodingo Step 1 Apply the S mapping to the block of ciphertext It the simple substitution that is mapping The S maps See Answer

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