public KdfResult DeriveKey(int keyLength, BitString keyMaster, BitString saltMaster, BitString kdr, BitString index, BitString srtcpIndex)
{
if (keyMaster.BitLength != 128 && keyMaster.BitLength != 192 && keyMaster.BitLength != 256)
{
return(new KdfResult("Invalid Master Key, must be 128, 192, or 256-bit"));
}
if (saltMaster.BitLength != 112)
{
return(new KdfResult("Invalid Master Salt, must be 112-bit"));
}
if (index.BitLength != 48)
{
return(new KdfResult("Invalid SRTP Index, must be 48-bit"));
}
if (srtcpIndex.BitLength != 32)
{
return(new KdfResult("Invalid SRTCP Index, must be 32-bit"));
}
// Ke = Encryption Key, Ka = Authentication Key (for a HMAC-SHA-1), Ks = Salting Key
var srtpKe = Kdf(keyLength, keyMaster, saltMaster, kdr, index, new BitString("00"));
var srtpKa = Kdf(160, keyMaster, saltMaster, kdr, index, new BitString("01"));
var srtpKs = Kdf(112, keyMaster, saltMaster, kdr, index, new BitString("02"));
var srtpResult = new SrtpResult(srtpKe, srtpKa, srtpKs);
var srtcpKe = Kdf(keyLength, keyMaster, saltMaster, kdr, srtcpIndex, new BitString("03"));
var srtcpKa = Kdf(160, keyMaster, saltMaster, kdr, srtcpIndex, new BitString("04"));
var srtcpKs = Kdf(112, keyMaster, saltMaster, kdr, srtcpIndex, new BitString("05"));
var srtcpResult = new SrtpResult(srtcpKe, srtcpKa, srtcpKs);
return(new KdfResult(srtpResult, srtcpResult));
}
public KdfResult(SrtpResult srtp, SrtpResult srtcp)
{
SrtpResult = srtp;
SrtcpResult = srtcp;
}
