Creating -Cryptographic Context

Creating -Cryptographic Context -

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.

A cryptographic context includes a session key used in encryption and message -authentication. A cryptographic context also includes a securely exchanged -random bit string used to derive session keys called the master key. In addition -to the session and master key the cryptographic context includes other working -session parameters.

- -

Required background

Prior to cryptographic context -creation:

The master key,master -salt and parameters (ie. TSrtpCryptoParams) required to create the cryptographic -context must be created and initalised.

Procedure

The following steps describe the steps -involved in creating a cryptographic context:

Create a cryptographic -context by invoking the API NewL() or NewLC() of the class CSRTPCryptoContext.
1. - IMPORT_C static CSRTPCryptoContext* NewL( const CSRTPMasterKey* aKey, - const CSRTPMasterSalt* aSalt, - const TSrtpCryptoParams& aCryptoParams);
  
  aKey -is the input parameter that contains the master key.
  
  aSalt is the -input parameter that contains the master salt key.
  
  aCryptoParams is -the input parameter that contains the Crypto Context parameters.
  
  The -API leaves with KErrNone if successfully executed, else returns a valid system-wide -error code.
2. - IMPORT_C static CSRTPCryptoContext* NewLC( const CSRTPMasterKey* aKey, - const CSRTPMasterSalt* aSalt, - const TSrtpCryptoParams& aCryptoParams );
  
  aKey -is the input parameter that contains the master key.
  
  aSalt is the -input parameter that contains the master salt key.
  
  aCryptoParams is -the input parameter that contains the Crypto Context parameters.
  
  The -API leaves with KErrNone if successfully executed, else returns a valid system-wide -error code.

Creating Master Key

The master key can be created using -the following API's:

IMPORT_C static CSRTPMasterKey* NewL( const TDesC8& aKey,const TDesC8& aMKI,TUint aN_E = KSRTPDefSessionEncryptionKeyLength,Uint aN_A = KSRTPDefSessionAuthenticationKeyLength );
IMPORT_C static CSRTPMasterKey* NewLC( const TDesC8& aKey,const TDesC8& aMKI,TUint aN_E = KSRTPDefSessionEncryptionKeyLength,TUint aN_A = KSRTPDefSessionAuthenticationKeyLength);
IMPORT_C static CSRTPMasterSalt* NewLC( const TDesC8& aKey, TUint aN_S = KSRTPDefSessionSaltingKeyLength );

Creating Master Salt Key

The master salt key can be created -using the following API's:

IMPORT_C static CSRTPMasterSalt* NewL( const TDesC8& aKey,TUint aN_S = KSRTPDefSessionSaltingKeyLength )

- -

Results

On successful execution of the API, a cryptographic -context is created.

The cryptographic context can be used by a SRTP -session or Stream. In other words, the cryptographic context is owned by the -session or stream.

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

- -

For more information on cryptographic context management also -refer:

MasterKey()

SetMasterKey()

MasterSalt()

SetMasterSalt()

SetRCCm3Sync()

CryptoParams()

AddCryptoChangeObserver()

RemoveCryptoChangeObserver()

UpdateCryptoParams()

-Creating -an SRTP Session -Creating -an SRTP Stream -Encrypting - RTCP Packet Data -Encrypting -RTP Packet Data -Decrypting -RTP Packet Data -Decrypting - RTCP Packet Data -Updating -Master Key -Managing - Master Key + + + + + +Creating +Cryptographic Context +

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.

A cryptographic context includes a session key used in encryption and message +authentication. A cryptographic context also includes a securely exchanged +random bit string used to derive session keys called the master key. In addition +to the session and master key the cryptographic context includes other working +session parameters.

+ +

Required background

Prior to cryptographic context +creation:

The master key,master +salt and parameters (ie. TSrtpCryptoParams) required to create the cryptographic +context must be created and initalised.

Procedure

The following steps describe the steps +involved in creating a cryptographic context:

Create a cryptographic +context by invoking the API NewL() or NewLC() of the class CSRTPCryptoContext.
1. + IMPORT_C static CSRTPCryptoContext* NewL( const CSRTPMasterKey* aKey, + const CSRTPMasterSalt* aSalt, + const TSrtpCryptoParams& aCryptoParams);
  
  aKey +is the input parameter that contains the master key.
  
  aSalt is the +input parameter that contains the master salt key.
  
  aCryptoParams is +the input parameter that contains the Crypto Context parameters.
  
  The +API leaves with KErrNone if successfully executed, else returns a valid system-wide +error code.
2. + IMPORT_C static CSRTPCryptoContext* NewLC( const CSRTPMasterKey* aKey, + const CSRTPMasterSalt* aSalt, + const TSrtpCryptoParams& aCryptoParams );
  
  aKey +is the input parameter that contains the master key.
  
  aSalt is the +input parameter that contains the master salt key.
  
  aCryptoParams is +the input parameter that contains the Crypto Context parameters.
  
  The +API leaves with KErrNone if successfully executed, else returns a valid system-wide +error code.

Creating Master Key

The master key can be created using +the following API's:

IMPORT_C static CSRTPMasterKey* NewL( const TDesC8& aKey,const TDesC8& aMKI,TUint aN_E = KSRTPDefSessionEncryptionKeyLength,Uint aN_A = KSRTPDefSessionAuthenticationKeyLength );
IMPORT_C static CSRTPMasterKey* NewLC( const TDesC8& aKey,const TDesC8& aMKI,TUint aN_E = KSRTPDefSessionEncryptionKeyLength,TUint aN_A = KSRTPDefSessionAuthenticationKeyLength);
IMPORT_C static CSRTPMasterSalt* NewLC( const TDesC8& aKey, TUint aN_S = KSRTPDefSessionSaltingKeyLength );

Creating Master Salt Key

The master salt key can be created +using the following API's:

IMPORT_C static CSRTPMasterSalt* NewL( const TDesC8& aKey,TUint aN_S = KSRTPDefSessionSaltingKeyLength )

+ +

Results

On successful execution of the API, a cryptographic +context is created.

The cryptographic context can be used by a SRTP +session or Stream. In other words, the cryptographic context is owned by the +session or stream.

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

+ +

For more information on cryptographic context management also +refer: