IETF71, Philadelphia, March 2008 draft-wing-avt-dtls-srtp-key-transport-01 1

draft-wing-avt-dtls-srtp-key-transport-01

Dan Wing, dwing@cisco.com

MSEC Working Group

DTLS-SRTP Key Transport

IETF71, Philadelphia, March 2008 draft-wing-avt-dtls-srtp-key-transport-01 2

Overview

• IETF68 (Prague), RTPSEC BoF selected DTLS-SRTP as the preferred SRTP keying mechanism

• Only unicast, point-to-point was in scope

• DTLS-SRTP Key Transport allows efficient SRTP operation for– Several unicast conferencing scenarios– Multicast

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Why Consider DTLS-SRTP for Multicast?

• DTLS-SRTP works for group of 2

• GDOI-SRTP is overkill for a group of 3– Useful for a larger group

• DTLS-SRTP-Key-Transport allows optimizing SRTP keying for ‘small groups’

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Operation of DTLS-SRTP Key Transport

for Multicast

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DTLS-SRTP-Key-Transport

• DTLS-SRTP-Key-Transport is negotiated during TLS handshake

• DTLS-SRTP session stays up for duration of call

• SRTP key is sent within the DTLS session itself– As a new TLS content-type

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DTLS session with each listener

1. Each listener establishes unicast DTLS-SRTP session with speaker

2. Speaker uses DTLS-SRTP Key Transport to tell every listener the same SRTP key

speaker

Listener 1

Listener 2

Listener 3

DTLS-SRTP, transport speaker’s SRTP key “A”

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SRTP multicasting

• SRTP packets are then multicasted to listeners

speaker

Listener 1

Listener 2

Listener 3

SRTP packet, key “A”

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DTLS-SRTP-Key-Transport

• DTLS-SRTP-Key-Transport is negotiated during TLS handshake

• DTLS-SRTP session stays up for duration of call

• SRTP key is sent within the DTLS session itself– As a new TLS content-type

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Questions

draft-wing-avt-dtls-srtp-key-transport-01

Dan Wing, dwing@cisco.com