36 lines
1.5 KiB
Markdown
36 lines
1.5 KiB
Markdown
Shuffle Table Generator
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=======================
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The `LicenseKey` class converts a GUID (or any 128 bits of data) into a license key similar
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to the ones used by Microsoft products (5 groups of 5 alphanumeric characters).
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For additional obfuscation, bits can be mapped in a random order. That will offer some
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protection when you have, for example, a running serial number. With shuffling, each
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increment will result in likely several alphanumeric characters changing in seemingly
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unpredictable ways (base-2 to base-36 conversion pretty much guarantees that any small
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change affects many following alphanumeric "digits").
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/// <summary>Generates a new random shuffle table</summary>
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/// <param name="iterationCount">
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/// Number of iterations in which to randomize the shuffle table
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/// </param>
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/// <returns>The new random shuffle table</returns>
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public static byte[] generateShuffleTable(int iterationCount) {
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byte[] shuffleTable = new byte[128];
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for(int index = 0; index < 128; ++index)
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shuffleTable[index] = index;
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Random rng = new Random();
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for(int iteration = 0; iteration < iterationCount; ++iteration) {
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int firstIndex = rng.Next() % 128;
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int secondIndex = rng.Next() % 128;
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byte temp = shuffleTable[firstIndex];
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shuffleTable[firstIndex] = shuffleTable[secondIndex];
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shuffleTable[secondIndex] = temp;
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}
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return shuffleTable;
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}
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