For the case someone wants all or part of their updates encrypted, updates are encrypted with a symmetric key, and all friends get a copy of that key, signed for their eyes only using the public key of the friend, and possibly the private key of the user for authenticity.
For the case someone wants all or part of their updates encrypted, updates are encrypted with a symmetric key, and all friends get a copy of that key, signed for their eyes only using the public key of the friend, and possibly the private key of the user for authenticity.