$$ \newcommand \pk {\mathrm{pk}} \newcommand \sk {\mathrm{sk}} \newcommand \Vote {\mathrm{Vote}} \newcommand \fv {\text{first}} \newcommand \Record {\mathrm{Record}} \newcommand \lv {\text{last}} \newcommand \Stake {\mathrm{Stake}} \newcommand \Seed {\mathrm{Seed}} \newcommand \CommitteeThreshold {\mathrm{CommitteeThreshold}} \newcommand \CommitteeSize {\mathrm{CommitteeSize}} \newcommand \Sign {\mathrm{Sign}} $$

Broadcast Rules

Upon observing messages or receiving timeout events, the player state machine emits network outputs, which are externally visible. The player may also append an entry to the ledger.

A correct player emits only valid votes. Suppose the player is identified with the address \( I \) and possesses the secret key \( \sk \), and the agreement is occurring on the ledger \(L\). Then the player constructs a vote \( \Vote(I, r, p, s, v) \) by doing the following:

• Let

  • \(( \pk, B, r_\fv, r_\lv) = \Record(L, r - \delta_b, I) \),
  • \( \bar{B} = \Stake(L, r - \delta_b) \),
  • \( Q = \Seed(L, r - \delta_s) \),
  • \( \tau = \CommitteeThreshold(s) \),
  • \( \bar{\tau} = \CommitteeSize(s) \).

• Encode \( x := (I, r, p, s, v), x’ := (I, r, p, s) \).

• Try to set \( y := \Sign(x, x’, \sk, B, \bar{B}, Q, \tau, \bar{\tau}) \).

If the signing procedure succeeds, the player broadcasts \( Vote(I, r, p, s, v) = (I, r, p, s, v, y) \). Otherwise, the player does not broadcast anything.

For certain broadcast vote-messages specified here, a node is forbidden to equivocate (i.e., produce a pair of votes which contain the same round, period, and step but which vote for different proposal values). These messages are marked with an asterisk (*) below. To prevent accidental equivocation after a power failure, nodes SHOULD checkpoint their state to crash-safe storage before sending these messages.

For further details on these checkpoint strategies, refer to the non-normative Ledger specification. For an in-depth review of broadcasting functionalities, refer to the non-normative Network specification.