65 lines
1.8 KiB
D
65 lines
1.8 KiB
D
import std.stdio;
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import std.string;
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immutable L_ALPHABET = "HXUCZVAMDSLKPEFJRIGTWOBNYQ";
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immutable R_ALPHABET = "PTLNBQDEOYSFAVZKGJRIHWXUMC";
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enum Mode {
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ENCRYPT,
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DECRYPT,
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}
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string exec(string text, Mode mode, bool showSteps = false) {
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char[] left = L_ALPHABET.dup;
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char[] right = R_ALPHABET.dup;
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char[] eText;
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eText.length = text.length;
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char[26] temp;
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foreach (i; 0..text.length) {
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if (showSteps) writeln(left, ' ', right);
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int index;
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if (mode == Mode.ENCRYPT) {
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index = right.indexOf(text[i]);
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eText[i] = left[index];
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} else {
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index = left.indexOf(text[i]);
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eText[i] = right[index];
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}
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if (i == text.length - 1) break;
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// permute left
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foreach (j; index..26) temp[j - index] = left[j];
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foreach (j; 0..index) temp[26 - index + j] = left[j];
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auto store = temp[1];
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foreach (j; 2..14) temp[j - 1] = temp[j];
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temp[13] = store;
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left = temp.dup;
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// permute right
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foreach (j; index..26) temp[j - index] = right[j];
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foreach (j; 0..index) temp[26 - index + j] = right[j];
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store = temp[0];
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foreach (j; 1..26) temp[j - 1] = temp[j];
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temp[25] = store;
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store = temp[2];
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foreach (j; 3..14) temp[j - 1] = temp[j];
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temp[13] = store;
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right = temp.dup;
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}
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return eText.idup;
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}
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void main() {
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auto plainText = "WELLDONEISBETTERTHANWELLSAID";
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writeln("The original plaintext is : ", plainText);
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writeln("\nThe left and right alphabets after each permutation during encryption are :\n");
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auto cipherText = exec(plainText, Mode.ENCRYPT, true);
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writeln("\nThe ciphertext is : ", cipherText);
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auto plainText2 = exec(cipherText, Mode.DECRYPT);
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writeln("\nThe recovered plaintext is : ", plainText2);
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}
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