/// <summary>
/// SHA1算法的分组处理方法,分为4轮,每轮20个步骤,总计80个步骤
/// </summary>
/// <param name="statuBit">初始状态位</param>
/// <param name="w0_w79">与某个分组对应的w0~w79的值</param>
/// <returns>计算得到的状态位,若该分组为最后一个分组,则此返回值为最终SHA1值</returns>
private byte[] SHA1GroupProcessing(byte[] statuBit, byte[][] w0_w79)
{
byte[] result = new byte[160 / 8];
Array.Copy(statuBit, result, 160 / 8);
//处理分组时的80个步骤
for (int i = 0; i < 80; ++i)
{
//将160bit(20Byte)分成5个缓存区(5个UInt32)
UInt32 buffA = MyBitConverter.ToUInt32(result, 0),
buffB = MyBitConverter.ToUInt32(result, 4),
buffC = MyBitConverter.ToUInt32(result, 8),
buffD = MyBitConverter.ToUInt32(result, 12),
buffE = MyBitConverter.ToUInt32(result, 16);
//将缓存区A,B,C,D复制到B,C,D,E中
Array.Copy(MyBitConverter.GetBytes(buffA), 0, result, 4, 4);
Array.Copy(MyBitConverter.GetBytes((buffB << 30) | (buffB >> 2)), 0, result, 8, 4);
Array.Copy(MyBitConverter.GetBytes(buffC), 0, result, 12, 4);
Array.Copy(MyBitConverter.GetBytes(buffD), 0, result, 16, 4);
//计算逻辑函数Fi和步骤相关的Ki,wt
UInt32 fi = 0, ki = 0, wt = MyBitConverter.ToUInt32(w0_w79[i], 0);
if (i < 20)
{
fi = (buffB & buffC) | (~buffB & buffD);
ki = 0x5a827999;
}
else if (i < 40)
{
fi = buffB ^ buffC ^ buffD;
ki = 0x6ed9eba1;
}
else if (i < 60)
{
fi = (buffB & buffC) | (buffC & buffD) | (buffD & buffB);
ki = 0x8f1bbcdc;
}
else if (i < 80)
{
fi = buffB ^ buffC ^ buffD;
ki = 0xca62c1d6;
}
//将缓存区A循环左移5位
buffA = (buffA << 5) | (buffA >> 27);
//计算E并将结果复制到A中
buffE = buffE + fi + buffA + wt + ki;
Array.Copy(MyBitConverter.GetBytes(buffE), 0, result, 0, 4);
}
//将处理前160bit状态和处理后160bit状态相加
for (int i = 0; i < 5; ++i)
{
UInt32 oldNum = MyBitConverter.ToUInt32(statuBit, 4 * i), newNum = MyBitConverter.ToUInt32(result, 4 * i);
Array.Copy(MyBitConverter.GetBytes(oldNum + newNum), 0, result, 4 * i, 4);
}
return(result);
}
/// <summary>
/// SHA1算法计算指定分组的w0~w79数据的方法
/// </summary>
/// <param name="group">需要计算的分组</param>
/// <returns>计算得到的w0~w79</returns>
private byte[][] SHA1W0_W79(byte[] group)
{
byte[][] w0_w79 = new byte[80][];
//将输入分组的512bit作为w0_w15
for (int i = 0; i < 16; ++i)
{
w0_w79[i] = new byte[32 / 8];
Array.Copy(group, i * 4, w0_w79[i], 0, 32 / 8);
}
for (int i = 16; i < 80; ++i)
{
//异或求值后循环左移1bit
UInt32 wt =
MyBitConverter.ToUInt32(w0_w79[i - 16]) ^
MyBitConverter.ToUInt32(w0_w79[i - 14]) ^
MyBitConverter.ToUInt32(w0_w79[i - 8]) ^
MyBitConverter.ToUInt32(w0_w79[i - 3]);
wt = (wt << 1) | (wt >> 31);
//对W_t进行赋值
w0_w79[i] = MyBitConverter.GetBytes(wt);
}
return(w0_w79);
}