challenge: What is the primary difference between implicit certificates and identity-based cryptography?
  
  A. Implicit certificates are used for authentication, while ID-based schemes are used for authorization
  B. Implicit certificates use the subject's identity to derive their public key, while ID-based schemes do not
  C. Implicit certificates are used for encryption, while ID-based schemes are used for decryption
  D. Implicit certificates use a trusted third party to issue private keys, while ID-based schemes do not
  Answer: 