plaintext decrypted form a cipher text using key = 3 in Caesar Cipher and that plain text with the following ciphertext to get the key 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.
Take original plain text as &quot; PLEASEEECUSEMYDEARAUNTSALLY&quot;, note that I've ignored the 'X', so that rail fence with key(row depth) = 4 cipher text will be &quot;PEMALLEEEYRUALESCSDANSYAUET&quot; now using Caesar cipher with k=4 on this new text.
${C= (P+k)mod26}$ , you will get cipher as $${"TIQEPPIBICVYEPIWGWHERWCEYIX"}$$



Here we take row wise so P --&gt; T, E--&gt;I, M--&gt;Q, A--&gt;E, L--&gt;P,
in second row L--&gt;P,E--&gt;I and so on...