Data update

Task/Chaocipher/Pluto/chaocipher.pluto

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+require "table2"
+
+enum chao begin
+    encrypt,
+    decrypt
+end
+
+local function exec(text, mode, show_steps)
+    local len = #text
+    local left  = "HXUCZVAMDSLKPEFJRIGTWOBNYQ"
+    local right = "PTLNBQDEOYSFAVZKGJRIHWXUMC"
+    local etext = table.rep(len, 0)
+    local temp  = table.rep(26, "")
+    for i = 1, len do
+        if show_steps then print($"{left}  {right}") end
+        local index
+        if mode == chao.encrypt then
+            index = right:find(text[i], 1, true)
+            etext[i] = left[index]
+        else
+            index = left:find(text[i], 1, true)
+            etext[i] = right[index]
+        end
+        if i == len then break end
+
+        -- Permute left.
+        for j = index, 26 do temp[j - index + 1] = left[j] end
+        for j = 1, index - 1 do temp[27 - index + j] = left[j] end
+        local store = temp[2]
+        for j = 3, 14 do temp[j - 1] = temp[j] end
+        temp[14] = store
+        left = temp:concat("")
+
+        -- Permute right.
+        for j = index, 26 do temp[j - index + 1] = right[j] end
+        for j = 1, index - 1 do temp[27 - index + j] = right[j] end
+        store = temp[1]
+        for j = 2, 26 do temp[j - 1] = temp[j] end
+        temp[26] = store
+        store = temp[3]
+        for j = 4, 14 do temp[j - 1] = temp[j] end
+        temp[14] = store
+        right = temp:concat("")
+    end
+    return etext:concat("")
+end
+
+local plain_text = "WELLDONEISBETTERTHANWELLSAID"
+print($"The original plaintext is : {plain_text}")
+io.write("\nThe left and right alphabets after each permutation ")
+print("during encryption are :\n")
+local cipher_text = exec(plain_text, chao.encrypt, true)
+print($"\nThe ciphertext is : {cipher_text}")
+local plain_text2 = exec(cipher_text, chao.decrypt, false)
+print($"\nThe recovered plaintext is : {plain_text2}")