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<task id="GUID-372B7A9F-261E-5F3F-B114-4BE2FE2EF7C7" xml:lang="en"><title>Creating

a SRTP Stream</title><abstract><p>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.  </p><p> 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). The stream can be

a incoming or outgoing.  </p></abstract><prolog><metadata><keywords/></metadata></prolog><taskbody>

<prereq><p>Prior to stream creation: </p> <ul>

<li id="GUID-A5BAEFAD-4D7E-55E8-8C7E-6D0050E4EA51"><p>A SRTP session must

be created and initialised. </p> </li>

<li id="GUID-D39A619E-3302-555C-BA48-437438E87A90"><p>Values to populate the

cryptographic context for the stream shall be available. </p> <p>The callback

object (for MSRTPReKeyingObserver) shall be implemented . </p> </li>

</ul> </prereq>

<steps id="GUID-CABD5696-FCB4-57FD-953D-2DCB97FF7021">

<step id="GUID-D9014EE0-7D97-5C29-B37E-E09E1A421705"><cmd>Create a SRTP stream

(incoming) by invoking the <xref href="GUID-86044C21-B6E7-3A38-AEA1-DC1DF372DAAE.dita"><apiname>NewL()</apiname></xref> of

the class <xref href="GUID-86044C21-B6E7-3A38-AEA1-DC1DF372DAAE.dita"><apiname>CSRTPStreamIn</apiname></xref>. </cmd>

<info>The functions <xref href="GUID-86044C21-B6E7-3A38-AEA1-DC1DF372DAAE.dita"><apiname>NewL()</apiname></xref> has six

variants. Each of the variants are explained below. </info>

<substeps id="GUID-F852D7E8-4434-53DF-92F5-DEE5EEB5A009">

<substep id="GUID-CF0C39A0-E813-5FEA-91FE-8548F74559B8"><cmd/>

<stepxmp><codeblock id="GUID-5E7C4FF4-FBBB-5B31-AC1E-F1CDE07152E8" xml:space="preserve">

                     IMPORT_C static CSRTPStreamIn* NewL( CSRTPSession& aSession,

                                      TUint aSSRC);</codeblock> </stepxmp>

<info>This API is appropriate when the stream uses the cryptographic context

of the session. </info>

<stepxmp>aSession is the input parameter that contains the session. The stream

will use the cryptographic context of the session. </stepxmp>

<stepxmp>aSSRC is the input parameter that contains the synchronization source

ID of the SRTP stream. </stepxmp>

<stepresult>The API leaves with KErrNone if successfully executed, else returns

a valid system-wide error code. </stepresult>

</substep>

<substep id="GUID-685A0114-7E49-5F44-BA72-D012D9F949D7"><cmd/>

<stepxmp><codeblock id="GUID-AD168026-EC51-5685-8C8E-A8C3968DB47B" xml:space="preserve">

                     IMPORT_C static CSRTPStreamIn* NewL( CSRTPSession& aSession,

                                      TUint aSSRC,

                                      CSRTPCryptoContext* aCon,

                                      MSRTPReKeyingObserver&amp; aObs );</codeblock> </stepxmp>

<info>This API is appropriate when the stream will have a cryptographic context

of its own. </info>

<stepxmp>aSession is the input parameter that contains the session. </stepxmp>

<stepxmp>aSSRC is the input parameter that contains the synchronization source

ID of the SRTP stream. </stepxmp>

<stepxmp>aCon is the input parameter that contains cryptographic context of

the SRTP stream. </stepxmp>

<stepxmp>aObs is the callback object. </stepxmp>

<stepresult>The API leaves with KErrNone if successfully executed, else returns

a valid system-wide error code. </stepresult>

</substep>

<substep id="GUID-160B8669-5CC2-5B80-9639-8FC80493A4C6"><cmd/>

<stepxmp><codeblock id="GUID-91CB350B-6572-5250-A08C-A1150CB59468" xml:space="preserve">

                     IMPORT_C static CSRTPStreamIn* NewL( CSRTPSession&amp; aSession);</codeblock> </stepxmp>

<info>This API is appropriate when the stream will use the cryptographic context

of the session. No synchronisation source id is provided at the time of stream

creation. The stream uses late binding. </info>

<stepxmp>aSession is the input parameter that contains the session. </stepxmp>

<stepresult>The API leaves with KErrNone if successfully executed, else returns

a valid system-wide error code. </stepresult>

</substep>

<substep id="GUID-25FD7761-7ED8-5435-B772-2C61E2CD36CC"><cmd/>

<stepxmp><codeblock id="GUID-E126672C-D116-5567-9884-8F4D0D7B35E6" xml:space="preserve">

                     IMPORT_C static CSRTPStreamIn* NewL( CSRTPSession& aSession,

                                      CSRTPCryptoContext* aCon,

                                      MSRTPReKeyingObserver&amp; aObs );</codeblock> </stepxmp>

<info>This API is appropriate when the stream will have a cryptographic context

of its own. No synchronisation source id is provided at the time of stream

creation. The stream uses late binding. </info>

<stepxmp>aSession is the input parameter that contains the session. </stepxmp>

<stepxmp>aCon is the input parameter that contains cryptographic context of

the SRTP stream. </stepxmp>

<stepxmp>aObs is the callback object. </stepxmp>

<stepresult>The API leaves with KErrNone if successfully executed, else returns

a valid system-wide error code. </stepresult>

</substep>

<substep id="GUID-A0CF7B65-9696-5D19-A58F-A9CA9B6C81E3"><cmd/>

<stepxmp><codeblock id="GUID-2120336E-C154-5C64-9D89-E60A486BB062" xml:space="preserve">

                    IMPORT_C static CSRTPStreamIn* NewL( CSRTPSession& aSession,

                                      TUint aSSRC,

                                      MSRTPReKeyingObserver&amp; aObs );</codeblock> </stepxmp>

<info>This API is appropriate when the stream will have a cryptographic context

of its own. The cryptographic context is set later using <xref href="GUID-86044C21-B6E7-3A38-AEA1-DC1DF372DAAE.dita"><apiname>SetCryptoInL().</apiname></xref>  </info>

<stepxmp>aSession is the input parameter that contains the session. </stepxmp>

<stepxmp>aSSRC is the input parameter that contains the synchronization source

ID of the SRTP stream. </stepxmp>

<stepxmp>aObs is the callback object. </stepxmp>

<stepresult>The API leaves with KErrNone if successfully executed, else returns

a valid system-wide error code. </stepresult>

</substep>

<substep id="GUID-DD5D97B1-9170-5BD9-A484-EF3BD94DD7D3"><cmd/>

<stepxmp><codeblock id="GUID-B99F6769-1B3B-5D5E-B592-231D42960FF3" xml:space="preserve">

                     IMPORT_C static CSRTPStreamIn* NewL( CSRTPSession& aSession,

                                      MSRTPReKeyingObserver&amp; aObs ); </codeblock> </stepxmp>

<info>This API is appropriate when the stream will have a cryptographic context

of its own. The cryptographic context is set later using <xref href="GUID-86044C21-B6E7-3A38-AEA1-DC1DF372DAAE.dita"><apiname>SetCryptoInL().</apiname></xref> No

synchronisation source id is provided at the time of stream creation .The

stream uses late binding. </info>

<stepxmp>aSession is the input parameter that contains the session. </stepxmp>

<stepxmp>aObs is the callback object. </stepxmp>

<stepresult>The API leaves with KErrNone if successfully executed, else returns

a valid system-wide error code. </stepresult>

</substep>

</substeps>

</step>

<step id="GUID-2305B32B-0C0A-561A-8EAC-501DBB246632"><cmd>Create a SRTP stream

(outgoing) by invoking the <xref href="GUID-86044C21-B6E7-3A38-AEA1-DC1DF372DAAE.dita"><apiname>NewL()</apiname></xref> of

the class <xref href="GUID-86044C21-B6E7-3A38-AEA1-DC1DF372DAAE.dita"><apiname>CSRTPStreamOut</apiname></xref>. </cmd>

<info>The functions <xref href="GUID-86044C21-B6E7-3A38-AEA1-DC1DF372DAAE.dita"><apiname>NewL()</apiname></xref> has three

variants. Each of the variants are explained below. </info>

<substeps id="GUID-70902482-3118-5F45-85D1-4D35D82831BD">

<substep id="GUID-5A084F2A-85B7-59F9-8801-831A1B10057E"><cmd/>

<stepxmp><codeblock id="GUID-5BA8A9E3-7BAE-5409-854E-B6840D32C80E" xml:space="preserve">

                     IMPORT_C static CSRTPStreamOut* NewL( CSRTPSession&amp; aSession, TUint aSSRC );</codeblock> </stepxmp>

<info>This API is appropriate when the stream uses the cryptographic context

of the session. </info>

<stepxmp>aSession is the input parameter that contains the session. The stream

will use the cryptographic context of the session. </stepxmp>

<stepxmp>aSSRC is the input parameter that contains the synchronization source

ID of the SRTP stream. </stepxmp>

<stepresult>The API leaves with KErrNone if successfully executed, else returns

a valid system-wide error code. </stepresult>

</substep>

<substep id="GUID-86DC7C26-24BF-5973-8F46-90A716024F27"><cmd/>

<stepxmp><codeblock id="GUID-7E9DCEB2-6A34-5C3E-B944-9C558CCDA2F2" xml:space="preserve">

                     IMPORT_C static CSRTPStreamOut* NewL( CSRTPSession& aSession,

                                       TUint aSSRC,

                                       CSRTPCryptoContext* aCon,

                                       MSRTPReKeyingObserver& aObs );

        </codeblock> </stepxmp>

<info>This API is appropriate when the stream will have a cryptographic context

of its own. </info>

<stepxmp>aSession is the input parameter that contains the session. </stepxmp>

<stepxmp>aSSRC is the input parameter that contains the synchronization source

ID of the SRTP stream. </stepxmp>

<stepxmp>aCon is the input parameter that contains cryptographic context of

the SRTP stream. </stepxmp>

<stepxmp>aObs is the callback object. </stepxmp>

<stepresult>The API leaves with KErrNone if successfully executed, else returns

a valid system-wide error code. </stepresult>

</substep>

<substep id="GUID-08AEA9DC-88BC-56B5-8E6C-51C312875B19"><cmd/>

<stepxmp><codeblock id="GUID-ADDC31FE-6D66-5860-9B1B-ACFF9E9CCCBC" xml:space="preserve">

                    IMPORT_C static CSRTPStreamOut* NewL( CSRTPSession& aSession,

                                       TUint aSSRC,

                                       MSRTPReKeyingObserver&amp; aObs ); </codeblock> </stepxmp>

<info>This API is appropriate when the stream will have a cryptographic context

of its own. The cryptographic context is set later using <xref href="GUID-86044C21-B6E7-3A38-AEA1-DC1DF372DAAE.dita"><apiname>SetCryptoOutL().</apiname></xref>  </info>

<stepxmp>aSession is the input parameter that contains the session. </stepxmp>

<stepxmp>aSSRC is the input parameter that contains the synchronization source

ID of the SRTP stream. </stepxmp>

<stepxmp>aObs is the callback object. </stepxmp>

<stepresult>The API leaves with KErrNone if successfully executed, else returns

a valid system-wide error code. </stepresult>

</substep>

</substeps>

</step>

</steps>

<result><p>On successful execution of the API, a SRTP stream is created and

initialized. </p> </result>

<postreq><p>The cryptographic context of the stream can be deleted and the

stream can be re-initialised using <xref href="GUID-86044C21-B6E7-3A38-AEA1-DC1DF372DAAE.dita"><apiname>UpdateCryptoAndStatesL() </apiname></xref>. </p> </postreq>

</taskbody><related-links>

<link href="GUID-06370120-7738-5694-9A8C-3B5B1E3A4352.dita"><linktext>Creating

an SRTP                 Session</linktext></link>

<link href="GUID-425A208C-5D2D-55FD-8623-9E00006E2781.dita"><linktext>Creating

a                 Cryptographic Context</linktext></link>

<link href="GUID-79846EA2-33CD-5D01-8E96-6092C15BD839.dita"><linktext>Encrypting

                RTCP Packet Data</linktext></link>

<link href="GUID-922F292E-9420-593B-B226-2764C5F29DF9.dita"><linktext>Encrypting

RTP                 Packet Data</linktext></link>

<link href="GUID-6E1AC4C9-7CA3-503A-AFC0-BAF29CCA8290.dita"><linktext>Decrypting

RTP                 Packet Data</linktext></link>

<link href="GUID-F9A24A47-7A0B-5F6E-8B0A-B7A7BCC4EAFC.dita"><linktext>Decrypting

                RTCP Packet Data</linktext></link>

<link href="GUID-B9BD2E0A-F214-5344-91A6-E4E99F0D74C8.dita"><linktext>Updating

Master                 Key</linktext></link>

<link href="GUID-F9A24A47-7A0B-5F6E-8B0A-B7A7BCC4EAFC.dita"><linktext>Managing

                Master Key</linktext></link>

</related-links></task>