he is not able to decrypt messages secured with previous and later session keys derived from the same master key. (Note that, of course, a leaked master key reveals all the session keys derived from it.) SRTP relies on an external key management protocol to set up the initial master key. Two protocols specifically designed to be used with SRTP are ZRTP and MIKEY. There are also other methods to negotiate the SRTP keys. There are several vendors which offer products that use the SDES key exchange method. Interoperability and applications See for phones, servers and applications supporting SRTP. Telephony (VoIP) Asterisk (PBX) Web browser support Known browsers with SRTP support of some kind Blink (browser engine) family Chromium (web browser) supporting (but not universally) SRTP experimentally since 2016 Opera (web browser) Vivaldi (web browser) Web browser families with some level of SRTP in the mainline updating branches from the core rendering system Gecko (software) MSHTML (superseded, but minimal support existed at time of expiration) WebKit So far no known SRTP support exists for text based web browsers. Although SRTP could be used to operate in a VPN, in conjunction with web browsers, no VPN networks are known to be using it. Standards documents , Proposed Standard, The Secure Real-time Transport Protocol (SRTP) , Proposed Standard, Integrity Transform Carrying Roll-Over Counter for the Secure Real-time Transport Protocol (SRTP) , Standard 65, RTP Profile for Audio and Video Conferences with Minimal Control , Standard 64, RTP: A Transport Protocol for Real-Time Applications , Informational, HMAC: Keyed-Hashing for Message Authentication , Proposed Standard, AES-GCM Authenticated Encryption in the Secure Real-time Transport Protocol (SRTP) References Cryptographic protocols