3.1.3 Initialization

LastGoodSSRC must be initialized to zero when the RTP session is created.

For RTPME, the encryption key MUST be derived as follows:

  1. During negotiation, the encryption key phrase MUST be in base64-encoded format in the SDP as specified in [MS-SDP].

  2. The key phrase MUST be base64 decoded into a Unicode string.

  3. This Unicode string MUST be converted into a UTF-8 code point string.

  4. This UTF-8 code point string MUST be hashed using the message digest algorithm 5 (MD5) algorithm.

  5. The DES CBC key is the first 56 bits from output of the hash.