Remote Audio Output Protocol (RAOP) is an

Internet streaming Streaming media refers to multimedia delivered through a network for playback using a media player. Media is transferred in a ''stream'' of packets from a server to a client and is rendered in real-time; this contrasts with file downl ...

protocol based on

RTSP The Real-Time Streaming Protocol (RTSP) is an application-level network protocol designed for multiplexing and packetizing multimedia transport streams (such as interactive media, video and audio) over a suitable transport protocol. RTSP is ...

/ RTP authored by

Apple Inc. Apple Inc. is an American multinational corporation and technology company headquartered in Cupertino, California, in Silicon Valley. It is best known for its consumer electronics, software, and services. Founded in 1976 as Apple Comput ...

It powers the

AirPlay Airplay is how frequently a song is being played through broadcasting on radio stations. A song which is being played several times every day (spins) would have a significant amount of airplay. Music which became very popular on jukeboxes, in n ...

technology built into

AirPort Express The AirPort Express is a discontinued Wi-Fi base station product from Apple Inc., part of the AirPort product line. While more compact and in some ways simpler than another Apple Wi-Fi base station, the AirPort Extreme, the Express offers au ...

wireless ( 802.11b/g/n) access point as well as the

Apple TV Apple TV is a digital media player and a microconsole developed and marketed by Apple. It is a small piece of networking hardware that sends received media data such as video and audio to a TV or external display. Its media services include ...

. The major difference from RTSP is an initial asymmetric key verification made by

iTunes iTunes is a media player, media library, and mobile device management (MDM) utility developed by Apple. It is used to purchase, play, download and organize digital multimedia on personal computers running the macOS and Windows operating s ...

to verify it is communicating with an AirPort Express or an

(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. The RSA public key stored in iTunes was extracted by

Jon Lech Johansen Jon Lech Johansen (born November 18, 1983, in Harstad, Norway), also known as DVD Jon, is a Norwegian programmer who has worked on reverse engineering data formats. He wrote the DeCSS software, which decodes the Content Scramble System used fo ...

, enabling third-party software to stream music to an AirPort Express. The RSA private key stored in the

was extracted by James Laird, enabling simulation of an Airport Express. The Shairport-sync application which emulates Airport Express hardware is available.

References

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External links

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 Data transmission Network protocols