Algorithm 7 PrepareTxn.

PrepareTxn (x): If ${\mathrm{cert}}_{\mathrm{B}}$ = ⊥ then abort. receiver ← ${\mathrm{cert}}_{\mathrm{B}}$. Output [[timestamp, x], $\sigma$, receiver] where $\sigma \leftarrow$ Sign([timestamp, x], ${\mathrm{prk}}_{\mathrm{B}}$)