public byte[] Decrypt(byte[] input, out byte[] paramac)
{
byte[] block = new byte[16];
byte[] tblock = new byte[16];
byte[] tctr = new byte[16];
paramac = new byte[16];
int size = input.Length - 0x20;
byte[] outblock = new byte[size];
int i = 0;
Array.Copy(input, i, tblock, 0, 16);
while (size > 16)
{
byte[] oblock = Decrypt_Block(tblock, ref paramac);
Array.Copy(oblock, 0, outblock, i, 16);
size -= 16;
i += 16;
Array.Copy(input, i, tblock, 0, 16);
}
DSi_CTR cryptoctx = new DSi_CTR()
{
_Key = Key,
_Ctr = ctr.Clone() as byte[]
};
block = cryptoctx.Crypt(block);
Array.Copy(input, i, block, 0, size);
block = Decrypt_Block(block, ref paramac);
Array.Copy(block, 0, outblock, i, size);
return(outblock);
}
public byte[] Decrypt_Block(byte[] input, ref byte[] paramac)
{
DSi_CTR cryptoctx = new DSi_CTR()
{
_Key = Key,
_Ctr = ctr
};
byte[] output = cryptoctx.Crypt(input);
for (int i = 0; i < 16; i++)
{
mac[i] ^= output[15 - i];
}
AesManaged aesAlg = new AesManaged
{
Mode = CipherMode.ECB
};
ICryptoTransform encryptor = aesAlg.CreateEncryptor(Key, null);
mac = encryptor.TransformFinalBlock(mac, 0, 16);
for (int i = 0; i < 16; i++)
{
paramac[i] = Convert.ToByte(mac[15 - i] ^ S0[i]);
}
return(output);
}
public DSi_CCM(byte[] key, int maclength, int payloadlength, int assoclength, byte[] nonce)
{
this.Key = key;
this.maclen = maclength;
maclength = (maclength - 2) / 2;
payloadlength = (payloadlength + 15) & ~15;
mac[0] = Convert.ToByte((maclength << 3) | 2);
if (assoclength != 0)
{
mac[0] |= (1 << 6);
}
for (int i = 0; i < 12; i++)
{
mac[1 + i] = nonce[11 - i];
}
mac[13] = Convert.ToByte(payloadlength >> 16);
mac[14] = Convert.ToByte(payloadlength >> 8);
mac[15] = Convert.ToByte((payloadlength >> 0) % 256);
AesManaged aesAlg = new AesManaged
{
Mode = CipherMode.ECB
};
ICryptoTransform encryptor = aesAlg.CreateEncryptor(key, null);
mac = encryptor.TransformFinalBlock(mac, 0, 16);
ctr[0] = 2;
for (int i = 0; i < 12; i++)
{
ctr[1 + i] = nonce[11 - i];
}
ctr[13] = 0;
ctr[14] = 0;
ctr[15] = 0;
DSi_CTR cryptoctx = new DSi_CTR()
{
_Key = key,
_Ctr = ctr
};
S0 = cryptoctx.Crypt(null);
}
public byte[] Decrypt(byte[] buffer, byte[] metablock)
{
byte[] ctr = new byte[16];
byte[] dnonce = new byte[12];
byte[] scratchpad = new byte[16];
byte[] chkmac = new byte[16];
byte[] genmac = new byte[16];
byte[] blockcrypt = new byte[16];
int chksize;
Array.Copy(metablock, chkmac, 16);
Array.Copy(metablock, 16, ctr, 0, 16);
Array.Copy(metablock, 16, blockcrypt, 0, 16);
ctr[0] = 0;
ctr[13] = 0;
ctr[14] = 0;
ctr[15] = 0;
DSi_CTR cryptoctx = new DSi_CTR()
{
Key = Key,
Ctr = ctr
};
scratchpad = cryptoctx.Crypt(blockcrypt);
chksize = (scratchpad[13] << 16) | (scratchpad[14] << 8) | (scratchpad[15] << 0);
if (scratchpad[0] != 0x3A || chksize != buffer.Length - 0x20)
{
return(null);
}
Array.Copy(metablock, 17, dnonce, 0, 12);
DSi_CCM crypt = new DSi_CCM(Key, 16, buffer.Length - 0x20, 0, dnonce);
buffer = crypt.Decrypt(buffer, out genmac);
return(buffer);
}
