/**
* Perform Counter Mode AES encryption / decryption
*
* @param pkt
* the RTP packet to be encrypted / decrypted
*/
public void ProcessPacketAESCM(RawPacket pkt)
{
long ssrc = pkt.GetSSRC();
int seqNo = pkt.GetSequenceNumber();
#pragma warning disable CS0675 // Bitwise-or operator used on a sign-extended operand
long index = ((long)roc << 16) | seqNo;
#pragma warning restore CS0675 // Bitwise-or operator used on a sign-extended operand
ivStore[0] = saltKey[0];
ivStore[1] = saltKey[1];
ivStore[2] = saltKey[2];
ivStore[3] = saltKey[3];
int i;
for (i = 4; i < 8; i++)
{
ivStore[i] = (byte)((0xFF & (ssrc >> ((7 - i) * 8))) ^ this.saltKey[i]);
}
for (i = 8; i < 14; i++)
{
ivStore[i] = (byte)((0xFF & (byte)(index >> ((13 - i) * 8))) ^ this.saltKey[i]);
}
ivStore[14] = ivStore[15] = 0;
int payloadOffset = pkt.GetHeaderLength();
int payloadLength = pkt.GetPayloadLength();
cipherCtr.Process(cipher, pkt.GetBuffer(), payloadOffset, payloadLength, ivStore);
}
/**
* Perform F8 Mode AES encryption / decryption
*
* @param pkt
* the RTP packet to be encrypted / decrypted
*/
public void ProcessPacketAESF8(RawPacket pkt)
{
// 11 bytes of the RTP header are the 11 bytes of the iv
// the first byte of the RTP header is not used.
MemoryStream buf = pkt.GetBuffer();
buf.Read(ivStore, (int)buf.Position, 12);
ivStore[0] = 0;
// set the ROC in network order into IV
ivStore[12] = (byte)(this.roc >> 24);
ivStore[13] = (byte)(this.roc >> 16);
ivStore[14] = (byte)(this.roc >> 8);
ivStore[15] = (byte)this.roc;
int payloadOffset = pkt.GetHeaderLength();
int payloadLength = pkt.GetPayloadLength();
SrtpCipherF8.Process(cipher, pkt.GetBuffer(), payloadOffset, payloadLength, ivStore, cipherF8);
}