Creating +an SRTP Session

The SRTP library generates SRTP packets from the RTP or RTCP stream and +forwards the packets to the receiver. SRTP transforms incoming SRTP packets +to RTP/RTCP packets and passes them up the stack. The cryptographic state +information associated with each SRTP stream is termed the cryptographic context. +The state information is maintained by both the sender and receiver of SRTP +streams. If multiple SRTP streams exist within a given RTP session, then separate +cryptographic contexts must be maintained for each stream. Each stream is +identified by a Synchronisation Source (SSRC).

All actions on the RTP and RTCP streams require a valid SRTP session. Creation +and initialization of a SRTP session is a pre-requirement for all consequent +actions.

+ +

Required background

Prior to initiation of a create +session request, an application or a RTP stack must ensure:

Values to populate the +cryptographic context for the session to be created must be available
Destination Address +must be identified.

Procedure

Create a SRTP session +by invoking the NewL() or NewLC() API's of the class CSRTPSession.

The +functions NewL() and NewLC() both +have two variants each. Each of the variants are explained below.
1. + IMPORT_C static CSRTPSession* NewL(const TInetAddr& + aDestination )
  
  This API is appropriate +when each stream will have its own cryptographic context.
  
  aDestination +is the input parameter that contains the destination address, including the +port.
  
  The API leaves with KErrNone if successfully executed, else +returns a valid system-wide error code.
2. IMPORT_C static CSRTPSession* NewL( const TInetAddr& + aDestination, CSRTPCryptoContext* aCon, + MSRTPReKeyingObserver& aObs );
  
  This +API is appropraite when all streams will use the same cryptographic context +configured in the SRTP session.
  
  aDestination is the input parameter +that contains the destination address, including the port.
  
  aCon is +the input parameter that contains the default cryptographic context for the +session.
  
  aObs is the input parameter that contains the callback object.
  
  The +API leaves with KErrNone if successfully executed, else returns a valid system-wide +error code.
3. IMPORT_C static CSRTPSession* NewLC(const TInetAddr& + aDestination ); +
  
  This function creates a new SRTP session +and pushes it to CleanupStack.
  
  aDestination is the input parameter +that contains the destination address, including the port.
  
  The API +leaves with KErrNone if successfully executed, else returns a valid system-wide +error code.
4. IMPORT_C static CSRTPSession* NewLC(const TInetAddr& + aDestination, CSRTPCryptoContext* aCon, + MSRTPReKeyingObserver& aObs); +
  
  This function creates a new SRTP session +and pushes it to CleanupStack.
  
  This API is invoked if all streams +will use the same cryptographic context.
  
  aDestination is the input +parameter that contains the destination address, including the port.
  
  aCon +is the input parameter that contains the default cryptographic context for +the session.
  
  aObs is the input parameter that contains the callback +object.
  
  The API leaves with KErrNone if successfully executed, else +returns a valid system-wide error code.

+ +

Results

On successful execution of the API, a SRTP +session is created and initialized.

+ +

On creation of a valid SRTP session, the application can request +for encrypting and decrypting of RTP and RTCP streams, Updating SRTP Master +Key or Notification of Key Expiry.

The stream(s) associated with the +session are always owned by the session.

The cryptographic context +of the session may be owned by the stream or the session.

The master +keys and the master salt are owned by the cryptographic context.

When +an SRTP session is deleted, the Cryptographic context, the stream, the master +key and the mastersalt key associated with the session are deleted.

The +steps below describe the stream management techniques of a SRTP session:

Attach a stream to session +of by invoking the API AddStreamToList()of the class CSRTPSession.
void AddStreamToList(CSRTPStream *aStream);
This +API attaches the given stream to the session.
aStream is the input +parameter that contains the stream to be added to session.
Remove a stream to the +session by invoking the API RemoveStreamFromList()of the class CSRTPSession.
void RemoveStreamFromList(CSRTPStream *aStream);
This API removes the given stream from the session.
aStream is the +input parameter that contains the stream to be removed from the session.