| Remote Audio Output Protocol | |
| Is Stack: | No |
| Abbreviation: | RAOP |
| Purpose: | Internet streaming |
| Developer: | Apple Inc. |
| Based On: | RTSP / RTP |
| Osilayer: | Application layer (7) |
| Hardware: | AirPort Express, Apple TV |
Remote Audio Output Protocol (RAOP) is an Internet streaming protocol based on RTSP / RTP authored by Apple Inc.[1] 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.
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]