Home Accessory Protocol

PS. Character = Characteristic

Device - HomeKit end device (swith, camera, etc)

• mDNS name: MyCamera._hap._tcp.local.
• DeviceID - mac-like: 0E:AA:CE:2B:35:71
• HomeKit device is described by:
  • one or more Accessories - has AID and Services
  • Services - has IID, Type and Characters
  • Characters - has IID, Type, Format and Value

Client - HomeKit client (iPhone, iPad, MacBook or opensource library)

• ClientID - static random UUID
• ClientPublic/ClientPrivate - static random 32 byte keypair
• can pair with Device (exchange ClientID/ClientPublic, ServerID/ServerPublic using Pin)
• can auth to Device using ClientPrivate
• holding persistant Secure connection to device
• can read device Accessories
• can read and write device Characters
• can subscribe on device Characters change (Event)

Server - HomeKit server (soft on end device or opensource library)

• ServerID - same as DeviceID (using for Client auth)
• ServerPublic/ServerPrivate - static random 32 byte keypair

AAC ELD

Requires ffmpeg built with --enable-libfdk-aac

-acodec libfdk_aac -aprofile aac_eld 

SampleRate	RTPTime	constantDuration	objectType
8000	60	=8000/1000*60=480	39 (AAC ELD)
16000	30	=16000/1000*30=480	39 (AAC ELD)
24000	20	=24000/1000*20=480	39 (AAC ELD)
16000	60	=16000/1000*60=960	23 (AAC LD)
24000	40	=24000/1000*40=960	23 (AAC LD)

Useful links

• https://github.com/apple/HomeKitADK/blob/master/Documentation/crypto.md
• https://github.com/apple/HomeKitADK/blob/master/HAP/HAPPairingPairSetup.c
• Extracting HomeKit Pairing Keys
• HAP in AirPlay2 receiver
• HomeKit Secure Video Unofficial Specification
• Homebridge Camera FFmpeg
• https://github.com/ljezny/Particle-HAP/blob/master/HAP-Specification-Non-Commercial-Version.pdf