AbstractAxDecoder getDecoder(BinaryReader reader)
{
long startPosition = reader.BaseStream.Position;
char[] buffer = reader.ReadChars(4);
string bufStr = new string(buffer);
reader.BaseStream.Seek(startPosition, SeekOrigin.Begin);
if (bufStr.Equals("HSP2", StringComparison.Ordinal))
{
return(new Ax2Decoder());
}
else if (bufStr.Equals("HSP3", StringComparison.Ordinal))
{
Ax3Decoder decoder = new Ax3Decoder();
decoder.Dictionary = dictionary;
return(decoder);
}
throw new HspDecoderException("HSP2でもHSP3でもない形式");
}
internal static HspCryptoTransform CrackEncryption(byte[] plain, byte[] encrypted, Hsp3Dictionary dictionary)
{
int count = Math.Min(plain.Length, encrypted.Length);
if (count < 2)
{
throw new Exception("情報サイズが不足");
}
byte[] difBuffer = new byte[count];
//byte baseXor = plain[0];
byte prevByte = 0;
byte andByte = 0xFF;
byte orByte = 0x00;
for (int i = 0; i < count; i++)
{
difBuffer[i] = XorAddTransform.Dif(plain[i], prevByte);
prevByte = plain[i];
//difBuffer[i] ^= baseXor;
andByte &= difBuffer[i];
orByte |= difBuffer[i];
}
if ((andByte != 0x00) || (orByte != 0xFF))
{
throw new Exception("平文の情報が足りません");
}
List <XorAddTransform> transformList = new List <XorAddTransform>();
//deHSP100 総当りテスト。
for (int i = 0; i < 0x100; i++)
{
XorAddTransform xoradd;
bool ok = true;
byte add = (byte)(i & 0x7F);
xoradd.XorSum = (i >= 0x80);
xoradd.AddByte = add;
xoradd.XorByte = XorAddTransform.GetXorByte(add, difBuffer[0], encrypted[0], xoradd.XorSum);
//チェック
for (int index = 1; index < count; index++)
{
if (encrypted[index] != xoradd.Encode(difBuffer[index]))
{
ok = false;
break;
}
}
if (ok)
{
AbstractAxDecoder decoder = null;
if (plain[3] == 0x32)
{
decoder = new Ax2Decoder();
}
else
{
Ax3Decoder decoder3 = new Ax3Decoder();
decoder3.Dictionary = dictionary;
decoder = decoder3;
}
HspCryptoTransform decryptor = new HspCryptoTransform();
decryptor.xorAdd = xoradd;
byte[] buffer = (byte[])encrypted.Clone();
buffer = decryptor.Decryption(buffer);
MemoryStream stream = new MemoryStream(buffer);
BinaryReader reader = new BinaryReader(stream, Encoding.GetEncoding("SHIFT-JIS"));
try {
decoder.Decode(reader);
transformList.Add(xoradd);
} catch (Exception e) {
Console.WriteLine(e);
}
}
}
//候補が2つ以上ならアルゴリズムに問題アリ。
if (transformList.Count > 1)
{
throw new Exception("復号器の異常");
}
if (transformList.Count == 1)
{
HspCryptoTransform ret = new HspCryptoTransform();
ret.xorAdd = transformList[0];
return(ret);
}
return(null);
}
