26 lines
1.0 KiB
C#
26 lines
1.0 KiB
C#
namespace dnlib.Protection {
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public class RotateLeftShiftEncryptionOperation : IEncryptionInstruction {
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private readonly uint _xIndex;
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private readonly uint _kIndex;
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private readonly uint _c;
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public RotateLeftShiftEncryptionOperation(uint xIndex, uint kIndex, uint c) {
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_xIndex = xIndex;
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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 xIndex = _xIndex % length + start;
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int shift = (int)((encryptionParam[_kIndex] + _c) % 8);
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uint v = content[xIndex];
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content[xIndex] = (byte)((v << shift) | (v >> (8 - shift)));
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}
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public string GenerateDecryptExpression(string dataVarName, string dataLengthVarName, string keyVarName) {
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return $"{{ uint32_t xIndex = {_xIndex} % {dataLengthVarName}; uint32_t shift = (uint32_t)({keyVarName}[{_kIndex}] + {_c}u) % 8; {dataVarName}[xIndex] = (byte)(((uint32_t){dataVarName}[xIndex] >> shift) | ((uint32_t){dataVarName}[xIndex] << (8 - shift))); }}";
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}
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}
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}
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