US Patent 10137860 Remote keyless entry message authentication

Method and apparatus are disclosed for remote keyless entry authentication. An example remote keyless entry system includes a key fob and a vehicle. The key fob generates a secured message with a plaintext space and a ciphertext space. The vehicle (i) determines whether the key fob may be authorized based on first information in the plaintext space, (ii) decrypts an encrypted value in the ciphertext space based on a predicted full counter value, and (iii) determines whether the key fob is authorized based on second information in the encrypted value.