AirPlay Encryption

From iOS Security February 2014 (p.16)

AirPlay also utilizes the authentication IC to verify that receivers have been approved by Apple. AirPlay audio and video streams utilize the MFi-SAP (Secure Association Protocol), which encrypts communication between the accessory and device using ECDH key exchange (Curve25519) with 2048-bit RSA keys and AES-128 in CTR mode.