SharpSRTP v0.2.3 — nugetz
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jimm98y/ SharpSRTP v0.2.3 .NET FW4.8.1 .NET 8.0 .NET 10.0 .NET Std2.0
DTLS, DTLS-SRTP, SRTP/SRTCP client and server written in C#.
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$ dotnet add package SharpSRTPReadme SharpSRTP
DTLS, DTLS-SRTP and SRTP/SRTCP client and server written in C#.
Implements the following RFCs:
The Secure Real-time Transport Protocol (SRTP) RFC3711
Session Description Protocol (SDP) Security Descriptions for Media Streams RFC4568
The SEED Cipher Algorithm and Its Use with the Secure Real-Time Transport Protocol (SRTP) RFC5669
Datagram Transport Layer Security (DTLS) Extension to Establish Keys for the Secure Real-time Transport Protocol (SRTP) RFC5764
The Use of AES-192 and AES-256 in Secure RTP RFC6188
Encryption of Header Extensions in the Secure Real-time Transport Protocol (SRTP) RFC6904
AES-GCM Authenticated Encryption in the Secure Real-time Transport Protocol (SRTP) RFC7714
The ARIA Algorithm and Its Use with the Secure Real-Time Transport Protocol (SRTP) RFC8269
Double Encryption Procedures for the Secure Real-Time Transport Protocol (SRTP) RFC8723
SRTP Crypto Suites
Currently implemented SRTP Crypto Suites are:
AES_CM_128_HMAC_SHA1_80 RFC4568
AES_CM_128_HMAC_SHA1_32
DTLS-SRTP Protection Profiles
SRTP_AES128_CM_HMAC_SHA1_80 RFC5764
SRTP_AES128_CM_HMAC_SHA1_32 RFC5764
SRTP_NULL_HMAC_SHA1_80 RFC5764
SRTP_NULL_HMAC_SHA1_32 RFC5764
SRTP_AEAD_AES_128_GCM RFC7714
SRTP_AEAD_AES_256_GCM RFC7714
DOUBLE_AEAD_AES_128_GCM_AEAD_AES_128_GCM RFC8723
DOUBLE_AEAD_AES_256_GCM_AEAD_AES_256_GCM RFC8723
SRTP_ARIA_128_CTR_HMAC_SHA1_80 RFC8269
SRTP_ARIA_128_CTR_HMAC_SHA1_32 RFC8269
SRTP_ARIA_256_CTR_HMAC_SHA1_80 RFC8269
SRTP_ARIA_256_CTR_HMAC_SHA1_32 RFC8269
SRTP_AEAD_ARIA_128_GCM RFC8269
SRTP_AEAD_ARIA_256_GCM RFC8269
Thread Safety SharpSRTP is not thread-safe. If multiple threads need to access the same SRTP context, proper synchronization mechanisms must be implemented by the user.
DTLS The current DTLS implementation is based upon BouncyCastle and supports DTLS 1.2 only.
DTLS Server Start with generating the TLS certificate. Self-signed RSA SHA256 certificate can be generated as follows:
bool isRSA = true;
var rsaCertificate = DtlsCertificateUtils.GenerateCertificate("DTLS", DateTime.UtcNow.AddDays(-1), DateTime.UtcNow.AddDays(30), isRSA);
Create the DTLS server and subscribe the OnHandshakeCompleted event to get notified when a client connects:
DtlsServer server = new DtlsServer(rsaCertificate.Certificate, rsaCertificate.PrivateKey, SignatureAlgorithm.rsa, HashAlgorithm.sha256);
server.OnHandshakeCompleted += (sender, e) =>
{
...
};
Create the DTLS transport. Here we will use UDP on localhost, port 8888:
UdpDatagramTransport udpServerTransport = new UdpDatagramTransport("127.0.0.1:8888", null);
Wait for the client and perform DTLS handshake:
bool isShutdown = false;
while(!isShutdown)
{
DtlsTransport dtlsTransport = server.DoHandshake(
out string error,
udpServerTransport,
() =>
{
return udpServerTransport.RemoteEndPoint.ToString();
},
(remoteEndpoint) =>
{
return new UdpDatagramTransport(null, remoteEndpoint);
});
var session = Task.Run(() =>
{
...
});
}
Receive data from the client:
byte[] buffer = new byte[dtlsTransport.GetReceiveLimit()];
int receivedLength = dtlsTransport.Receive(buffer, 0, buffer.Length, 100);
dtlsTransport.Send(buffer, 0, buffer.Length);
To modify the offered crypto suites for the DTLS handshake, simply override GetSupportedCipherSuites and return a different set of crypto suites. To support a different version of DTLS, override GetSupportedVersions and return a different version. Note that as of January 2026, BouncyCastle still does not support DTLS 1.3.
DTLS Client Start with creating the TLS certificate. Certificate type of the client must match the certificate type on the server, meaning if the server uses RSA certificate, the client has to use RSA certificate as well:
var rsaCertificate = DtlsCertificateUtils.GenerateCertificate("DTLS", DateTime.UtcNow.AddDays(-1), DateTime.UtcNow.AddDays(30), true);
DtlsClient client = new DtlsClient(null, rsaCertificate.certificate, rsaCertificate.key, SignatureAlgorithm.rsa, HashAlgorithm.sha256);
Optionally, you can let the client auto-generate the matching certificate:
DtlsClient client = new DtlsClient();
Subscribe for OnHandshakeCompleted:
client.OnHandshakeCompleted += (sender, e) =>
{
...
};
Create the DTLS transport. Here we will use UDP on localhost, port 8888:
UdpDatagramTransport udpServerTransport = new UdpDatagramTransport(null, "127.0.0.1:8888");
DtlsTransport dtlsTransport = client.DoHandshake(out string error, udpClientTransport);
Receive data to the server:
dtlsTransport.Send(buffer, 0, buffer.Length);
Receive data from the server:
byte[] buffer = new byte[dtlsTransport.GetReceiveLimit()];
int receivedLength = dtlsTransport.Receive(buffer, 0, buffer.Length, 100);
dtlsTransport.Close();
SRTP SRTP implementation is designed to take RTP/RTCP and convert it to SRTP/SRTCP while maintaining the SRTP context. RTP/RTSP server and clients are out of the scope of this library, but for a fully working example based upon SharpRTSP please refer to the examples.
Server Generate a random SRTP master key for AES_CM_128_HMAC_SHA1_80 on the server:
string cryptoSuite = SrtpCryptoSuites.AES_CM_128_HMAC_SHA1_80;
byte[] MKI = null;
SrtpKeys keys = SrtpProtocol.CreateMasterKeys(cryptoSuite, MKI);
Obtain the generated master key + master salt to send it to the client:
byte[] masterKeySalt = keys.MasterKeySalt;
Create a new SRTP context using those keys:
SrtpSessionContext context = SrtpProtocol.CreateSrtpSessionContext(keys);
Client Create a new SRTP context using existing keys from the server:
string cryptoSuite = SrtpCryptoSuites.AES_CM_128_HMAC_SHA1_80;
byte[] masterKeySalt = ...
byte[] MKI = null;
SrtpKeys keys = SrtpProtocol.CreateMasterKeys(cryptoSuite, MKI, masterKeySalt);
SrtpSessionContext context = SrtpProtocol.CreateSrtpSessionContext(keys);
RTP To encrypt RTP and create SRTP:
byte[] rtp = ...
byte[] rtpBuffer = new byte[context.CalculateRequiredSrtpPayloadLength(rtp.Length)];
Buffer.BlockCopy(rtp, 0, rtpBuffer, 0, rtp.Length);
context.ProtectRtp(rtpBuffer, rtp.Length, out int length);
byte[] srtp = rtpBuffer.Take(length).ToArray();
To decrypt SRTP and create RTP:
byte[] srtp = ...
context.UnprotectRtp(srtp, srtp.Length, out int length);
byte[] rtp = srtp.Take(length).ToArray();
RTCP To encrypt RTCP and create SRTCP:
byte[] rtcp = ...
byte[] rtcpBuffer = new byte[context.CalculateRequiredSrtcpPayloadLength(rtcp.Length)];
Buffer.BlockCopy(rtcp, 0, rtcpBuffer, 0, rtcp.Length];
context.ProtectRtcp(rtcpBuffer, rtcp.Length, out int length);
byte[] srtcp = rtcpBuffer.Take(length).ToArray();
To decrypt SRTCP and create RTCP:
byte[] srtcp = ...
context.UnprotectRtcp(srtcp, srtcp.Length, out int length);
byte[] rtcp = srtcp.Take(length).ToArray();
Samples
DTLS-SRTP DTLS-SRTP uses a modified DTLS client/server with the "use_srtp" extension to negotiate the SRTP encryption parameters and derive the corresponding SRTP keys.
Server First generate the TLS certificate, this time it will be ECDsa:
bool isRSA = false;
var ecdsaCertificate = DtlsCertificateUtils.GenerateCertificate("WebRTC", DateTime.UtcNow.AddDays(-1), DateTime.UtcNow.AddDays(30), isRSA);
Create the DTLS-SRTP server:
var server = new DtlsSrtpServer(ecdsaCertificate.Certificate, ecdsaCertificate.PrivateKey, SignatureAlgorithm.ecdsa, HashAlgorithm.sha256);
Subscribe for OnSessionStarted:
server.OnSessionStarted += (sender, e) =>
{
var context = e.Context;
var clientTransport = e.ClientDatagramTransport;
...
};
Create the DTLS transport. Here we will use UDP on localhost, port 8888:
UdpDatagramTransport udpServerTransport = new UdpDatagramTransport("127.0.0.1:8888", null);
Wait for the client and perform DTLS handshake:
bool isShutdown = false;
while(!isShutdown)
{
DtlsTransport dtlsTransport = server.DoHandshake(
out string error,
udpServerTransport,
() =>
{
return udpServerTransport.RemoteEndPoint.ToString();
},
(remoteEndpoint) =>
{
return new UdpDatagramTransport(null, remoteEndpoint);
});
}
After the OnSessionStarted event is executed, you can use the Context to protect/unprotect data and clientTransport to send/receive SRTP.
Client Generate the TLS certificate, this time it will be ECDsa:
bool isRSA = false;
var ecdsaCertificate = DtlsCertificateUtils.GenerateCertificate("WebRTC", DateTime.UtcNow.AddDays(-1), DateTime.UtcNow.AddDays(30), isRSA);
Create the DTLS-SRTP client:
var client = new DtlsSrtpClient(ecdsaCertificate.Certificate, ecdsaCertificate.PrivateKey, SignatureAlgorithm.ecdsa, HashAlgorithm.sha256)
Subscribe for OnSessionStarted:
client.OnSessionStarted += (sender, e) =>
{
var context = e.Context;
var clientTransport = e.ClientDatagramTransport;
...
};
Create the DTLS transport. Here we will use UDP on localhost, port 8888:
UdpDatagramTransport udpServerTransport = new UdpDatagramTransport(null, "127.0.0.1:8888");
DtlsTransport dtlsTransport = client.DoHandshake(out string error, udpClientTransport);
After the OnSessionStarted event is executed, you can use the Context to protect/unprotect data and clientTransport to send/receive SRTP.
Compatibility .NET FW4.8.1
.NET 8.0
.NET 10.0
.NET Std2.0
