Remote Audio Output Protocol

Remote Audio Output Protocol (RAOP) is an Internet streaming protocol based on RTSP / RTP authored by Apple Inc.^[1][2] It powers the AirPlay technology built into AirPort Express wireless (802.11b/g/n) access point as well as the Apple TV.^[2]

The major difference from RTSP is an initial asymmetric key verification made by iTunes to verify it is communicating with an AirPort Express or an Apple TV (as opposed to a simulation), and vice versa. The data channel is also encrypted by AES, with a random key protected by the asymmetric key mentioned above.^{[citation needed]}

The RSA public key stored in iTunes was extracted by Jon Lech Johansen, enabling third-party software to stream music to an AirPort Express.^[3]

The RSA private key stored in the AirPort Express was extracted by James Laird, enabling simulation of an Airport Express.^[4]

The Shairport-sync application which emulates Airport Express hardware is available.^[5]

• Technical note to describe the Remote Audio Access Protocol (RAOP) as used in Apple iTunes to stream music to the Airport Express (ApEx)
• RAOP-play an open source implementation of the protocol