1. Why can’t Alice choose Bob’s blinding factor (rr) and nonce (kr) for him?
If Alice chooses Bob’s blinding factor and nonce for him, Alice can potentially respend those same funds even though they were sent to Bob.
2. Alice constructs a partial transaction and sends it to Bob. Why can’t Bob broadcast the transaction after choosing his blinding factor and nonce?
The reason Bob can’t immediately broadcast the transaction is that Alice still needs to generate the whole signature of the transaction consisting of both Alice’s partial signature and Bob’s whole signature.
3. What information does the transaction kernel contain?
The transaction kernel contains the signature of the transaction, the public key associated with the excess blinding factor, the transaction fee, and the lock_height.
4. What pieces of information are actually broadcast in a Grin transaction?
The only pieces of information broadcasted in a Grin transaction are the used input, new outputs, transaction kernel, and kernel offset.