公司有个lora项目，要用到Lora-ns，虽然有其他公司现成的解决方案，但是需要有我们自己的个性化逻辑，因此需要重新手写NS的相关代码，根据semtech公司制定的协议标准编写了C#版本的lora-ns。
其中里面有个AES128-CMAC在网上比较少，我也只在StackOverflow上找到了对应的算法逻辑，如下:
/// <summary>
/// 获取cmac
/// </summary>
/// <param name="key"></param>
/// <param name="data"></param>
/// <returns></returns>
public static byte[] Aes_Cmac(byte[] key, byte[] data)
{
// SubKey generation
// step 1, AES-128 with key K is applied to an all-zero input block.
byte[] L = AesEncrypt(key, new byte[16], new byte[16]);
// step 2, K1 is derived through the following operation:
byte[] FirstSubkey = Rol(L); //If the most significant bit of L is equal to 0, K1 is the left-shift of L by 1 bit.
if ((L[0] & 0x80) == 0x80)
FirstSubkey[15] ^= 0x87; // Otherwise, K1 is the exclusive-OR of const_Rb and the left-shift of L by 1 bit.
// step 3, K2 is derived through the following operation:
byte[] SecondSubkey = Rol(FirstSubkey); // If the most significant bit of K1 is equal to 0, K2 is the left-shift of K1 by 1 bit.
if ((FirstSubkey[0] & 0x80) == 0x80)
SecondSubkey[15] ^= 0x87; // Otherwise, K2 is the exclusive-OR of const_Rb and the left-shift of K1 by 1 bit.
// MAC computing
if (((data.Length != 0) && (data.Length % 16 == 0)) == true)
{
// If the size of the input message block is equal to a positive multiple of the block size (namely, 128 bits),
// the last block shall be exclusive-OR'ed with K1 before processing
for (int j = 0; j < FirstSubkey.Length; j++)
data[data.Length - 16 + j] ^= FirstSubkey[j];
}
else
{
// Otherwise, the last block shall be padded with 10^i
byte[] padding = new byte[16 - data.Length % 16];
padding[0] = 0x80;
data = data.Concat<byte>(padding.AsEnumerable()).ToArray();
// and exclusive-OR'ed with K2
for (int j = 0; j < SecondSubkey.Length; j++)
data[data.Length - 16 + j] ^= SecondSubkey[j];
}
// The result of the previous process will be the input of the last encryption.
byte[] encResult = AesEncrypt(key, new byte[16], data);
byte[] HashValue = new byte[16];
Array.Copy(encResult, encResult.Length - HashValue.Length, HashValue, 0, HashValue.Length);
return HashValue;
}
static byte[] Rol(byte[] b)
{
byte[] r = new byte[b.Length];
byte carry = 0;
for (int i = b.Length - 1; i >= 0; i--)
{
ushort u = (ushort)(b[i] << 1);
r[i] = (byte)((u & 0xff) + carry);
carry = (byte)((u & 0xff00) >> 8);
}
return r;
}
/// <summary>
/// AES加密
/// </summary>
/// <param name="clearTxt"></param>
/// <returns></returns>
public static byte[] AesEncrypt(byte[] keys, byte[] iv, byte[] data)
{
using (RijndaelManaged cipher = new RijndaelManaged())
{
cipher.Mode = CipherMode.CBC;
cipher.Padding = PaddingMode.None;
cipher.Key = keys;
cipher.IV = iv;
using (ICryptoTransform encryptor = cipher.CreateEncryptor())
{
using (MemoryStream ms = new MemoryStream())
{
using (CryptoStream writer = new CryptoStream(ms, encryptor, CryptoStreamMode.Write))
{
writer.Write(data, 0, data.Length);
writer.FlushFinalBlock();
return ms.ToArray();
}
}
}
}
}
本人对算法这块了解甚少，所以也不清楚代码内容的这些操作是什么具体含义，不过测试了数据该代码是可以通过，并且得出对应的MIC校验码。
同时，我也根据LoraWan的C源码找到了对应的camc代码，根据这个逻辑也写了个C#版本的cmac代码。如下：
#region 按照C-LoraWan协议编写C# cmac校验
public struct AesCmacCtx
{
public byte[] X;
public byte[] M_last;
public int M_n;
}
/// <summary>
/// 按照C-LoraWan协议编写C# cmac校验
/// </summary>
/// <param name="mixBxBuffer">数据载荷校验B0，否则为null</param>
/// <param name="buffer">待校验内容</param>
/// <param name="bufferSize">待校验内容长度</param>
/// <param name="key">待加密的秘钥</param>
public static byte[] ComputCmac(byte[] mixBxBuffer, byte[] buffer, int bufferSize, byte[] key)
{
AesCmacCtx ctx = new AesCmacCtx();
AES_CMAC_Init(ref ctx);
//*-*micBxBuffer
if (mixBxBuffer != null && mixBxBuffer.Length > 0)
{
AES_CMAC_Update(ref ctx, mixBxBuffer, key, 16);
}
AES_CMAC_Update(ref ctx, buffer, key, bufferSize);
AES_CMAC_Final(ref ctx, key, out byte[] Cmac);
return Cmac;
//string cmac;
//foreach (var item in Cmac)
//{
// Console.WriteLine(item.ToString("X2"));
//}
//cmac = (Cmac[0] << 24 | Cmac[1] << 16 | Cmac[2] << 8 | Cmac[3]).ToString("X8");
}
public static void AES_CMAC_Init(ref AesCmacCtx ctx)
{
ctx.X = new byte[16];
ctx.M_n = 0;
ctx.M_last = new byte[16];
}
public static void LSHIFT(byte[] v, ref byte[] r)
{
for (int i = 0; i < 15; i++)
{
r[i] = (byte)((v[i] << 1) | (v[i + 1] >> 7));
}
r[15] = (byte)(v[15] << 1);
}
public static void XOR(byte[] v, ref byte[] r)
{
for (int i = 0; i < 16; i++)
{
r[i] = (byte)(r[i] ^ v[i]);
}
}
public static void AES_CMAC_Update(ref AesCmacCtx ctx, byte[] data, byte[] appKey, int len)
{
int mlen = 0;
byte[] tempIn = new byte[16];
byte[] tempData;
if (ctx.M_n > 0)
{
mlen = Math.Min(16 - ctx.M_n, len);
for (int i = 0; i < mlen; i++)
{
ctx.M_last[ctx.M_n + i] = data[i];
}
ctx.M_n += mlen;
if (ctx.M_n < 16 || len == mlen)
return;
XOR(ctx.M_last, ref ctx.X);
Array.Copy(ctx.X, tempIn, 16);
tempIn = AesEncrypt(appKey, new byte[16], tempIn);
Array.Copy(tempIn, ctx.X, 16);
tempData = new byte[data.Length - mlen];
Array.Copy(data, mlen, tempData, 0, data.Length - mlen);
data = new byte[data.Length - mlen];
Array.Copy(tempData, data, tempData.Length);
len -= mlen;
}
while (len > 16)
{
XOR(data, ref ctx.X);
Array.Copy(ctx.X, tempIn, 16);
tempIn = AesEncrypt(appKey, new byte[16], tempIn);
Array.Copy(tempIn, ctx.X, 16);
tempData = new byte[data.Length - 16];
Array.Copy(data, 16, tempData, 0, data.Length - 16);
data = new byte[data.Length - 16];
Array.Copy(tempData, data, tempData.Length);
len -= 16;
}
Array.Copy(data, ctx.M_last, len);
ctx.M_n = len;
}
public static void AES_CMAC_Final(ref AesCmacCtx ctx, byte[] appKey, out byte[] Cmac)
{
Cmac = new byte[16];
byte[] tempK = new byte[16];
byte[] tempIn = new byte[16];
tempK = AesEncrypt(appKey, new byte[16], tempK);
if ((int)(tempK[0] & 0x80) > 0)
{
LSHIFT(tempK, ref tempK);
tempK[15] ^= 0x87;
}
else
LSHIFT(tempK, ref tempK);
if (ctx.M_n == 16)
{
XOR(tempK, ref ctx.M_last);
}
else
{
if ((int)(tempK[0] & 0x80) > 0)
{
LSHIFT(tempK, ref tempK);
tempK[15] ^= 0x87;
}
else
LSHIFT(tempK, ref tempK);
ctx.M_last[ctx.M_n] = 0x80;
while (++ctx.M_n < 16)
{
ctx.M_last[ctx.M_n] = 0x00;
}
XOR(tempK, ref ctx.M_last);
}
XOR(ctx.M_last, ref ctx.X);
Array.Copy(ctx.X, tempIn, 16);
tempIn = AesEncrypt(appKey, new byte[16], tempIn);
tempK = new byte[16];
Array.Copy(tempIn, Cmac, 16);
}
#endregion
该代码块也是亲测可用，算法逻辑都是和LoraWan的C源码一模一样
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