28 lines
1.1 KiB
C#
28 lines
1.1 KiB
C#
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namespace dnlib.Protection {
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public class Permute2EncryptionOperation : IEncryptionInstruction {
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private readonly uint _xIndex1;
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private readonly uint _kIndex;
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private readonly uint _c;
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public Permute2EncryptionOperation(uint xIndex1, uint kIndex, uint c) {
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_xIndex1 = xIndex1;
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_kIndex = kIndex % EncryptionInfo.KeyLength;
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_c = c;
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}
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public void Encrypt(byte[] content, uint start, uint length, byte[] encryptionParam) {
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uint xIndex1 = _xIndex1 % length + start;
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uint xIndex2 = (encryptionParam[_kIndex] + _c) % length + start;
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byte a = (byte)(content[xIndex1] + content[xIndex2]);
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byte b = (byte)(content[xIndex2] + 1);
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content[xIndex1] = a;
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content[xIndex2] = b;
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}
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public string GenerateDecryptExpression(string dataVarName, string dataLengthVarName, string keyVarName) {
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return $"{{ uint32_t xIndex1 = {_xIndex1} % {dataLengthVarName}; uint32_t xIndex2 = ((uint32_t){keyVarName}[{_kIndex}] + {_c}u) % {dataLengthVarName}; byte a = {dataVarName}[xIndex1]; byte b = {dataVarName}[xIndex2] - 1; {dataVarName}[xIndex1] = a - b; {dataVarName}[xIndex2] = b; }}";
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}
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}
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}
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