fusion idea: hiding number of players

[markblundeberg]

Right now any player can see how many players there are, by simply looking at the all-commitments or all-components lists. If there are 23 commitments/components per player then these lists will have length equal to 23 * number of players.

We can't really hide the input/output components since the players need to make an actual tx, but we can try to hide the blanks. To do this, I suspect this is secure:

• Blank components are not submitted in the covert submission phase
• During blame phase, it's still necessary to prove on blank commitments. Therefore the proof can include the blank component, and the unblinded signature over it. The verifier can verify the unblinded signatures.

To hide the commitments list is much more tricky. I'm not sure what is the best way.