HDCP(High-Bandwidth Digital Content Protection)
  • Authentication
    • First part
      1. The HDCP transmitter sends a message containing its public key - Aksv to the receiver. KSV(Key Selection Vector): This 20-bit binary value uniquely identifies the HDCP transmitter or receiver)
      2. The receiver returns its public key - Bksv.
      3. The transmitter examines the receiver’s public key to determine that it is valid, and calculates a secret key - Km based on the receiver’s public key and its own private key; the receiver also calculates a secret key - Km' based on the transmitter’s public key and its internal private key. (Km = Km')
      4. The receiver is expected to send an encrypted message RO' (RO' is generated using the secret key Km') to the transmitter within 100 ms of the initial contact by the transmitter.
      5. The transmitter matches RO' against its own internal RO (RO is generated using the secret key Km). If RO=RO', that would imply that Km=Km', and thus the receiver is initially authenticated.
    • Third part(link integrity check)
      1. The actual encryption keys(frame key Ki) are changed periodically during vertical blanking intervals.
      2. Every 128 video frames or at least once every two seconds, the receiver sends information to the transmitter(Ri), and the transmitter uses this information to verify that the devices are synchronized.
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