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ZRTP: Media Path Key Agreement for Unicast Secure RTP

ZRTP: Media Path Key Agreement for Unicast Secure RTP. April 2011 , RFC 6189 Author(s): P. Zimmermann, A. Johnston, J. Callas Speaker :Ted. Outline. Introduction Background ZRTP Conclusion Reference. Introduction.

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ZRTP: Media Path Key Agreement for Unicast Secure RTP

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  1. ZRTP: Media Path Key Agreement for Unicast Secure RTP April 2011 , RFC 6189 Author(s): P. Zimmermann, A. Johnston, J. Callas Speaker :Ted

  2. Outline • Introduction • Background • ZRTP • Conclusion • Reference

  3. Introduction • ZRTP is a key-agreement protocol to negotiate the keys for encryption in a VoIP. • It uses Diffie-Hellman key exchange and the Secure Real-time Transport Protocol (SRTP) for encryptioneement protocol.

  4. Background • SIP

  5. Background(cont.) • Secure Real-time Transport Protocol (SRTP)

  6. ZRTP

  7. ZRTP(cont.) • Hello message • Usually sent at the start of an RTP session to determine if the other endpoint supports ZRTP. • The purpose of the Hello message is to confirm that the endpoint supports the protocol.

  8. ZRTP(cont.) • Commit message • The Commit message may be sent immediately after both endpoints have completed the Hello/HelloACK discovery handshake. • Deterministically choose the same DH key size and algorithm.

  9. ZRTP(cont.) • DHPart message • The Diffie-Hellman public values are exchanged in the DHPart1 and DHPart2 messages. p=23 and g=5. If Bob chooses b=15 B = 515 mod 23 = 19 K = 815 mod 23 K=2 If Alice chooses a=6 A = 56 mod 23 = 8 K = 196 mod 23 K=2

  10. ZRTP(cont.) • Confirm message • The Confirm1 message is sent by the Responder in response to a valid DHPart2 message after the SRTP session key and parameters have been negotiated.

  11. ZRTP(cont.)

  12. Conclusion • This protocol does not require prior shared secrets or rely on a Public key infrastructure (PKI) or on certification authorities • ZRTP can be used with any signaling protocol, including SIP, H.323.

  13. Reference • ZRTP: Media Path Key Agreement for Unicast Secure RTP • http://en.wikipedia.org/wiki/Diffie-Hellman_key_exchange

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