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how to use the plaintext from that was decrypted form a cipher text using key = 3 in Caesar Cipher and using that plain text with the following ciphertext to get the key.

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  • $\begingroup$ for the second exercise: k=4, you have to arrange ciphertext in rail fence and then u can get plain text. $\endgroup$ – SSA Jan 17 at 11:20
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  • Take original plain text as " PLEASEEECUSEMYDEARAUNTSALLY", note that I've ignored the 'X', so that rail fence with key(row depth) = 4 cipher text will be "PEMALLEEEYRUALESCSDANSYAUET" now using Caesar cipher with k=4 on this new text.
  • ${C= (P+k)mod26}$ , you will get cipher as $${"TIQEPPIBICVYEPIWGWHERWCEYIX"}$$
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  • Here we take row wise so P --> T, E-->I, M-->Q, A-->E, L-->P,
  • in second row L-->P,E-->I and so on...
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  • $\begingroup$ @user86282, Did you find the answer, if yes , then accept the answer. $\endgroup$ – SSA Jan 19 at 10:06

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