Algorithm 3 Deposit protocol.

Alice sends [Deposit, x] to BS. Upon receiving [Deposit, x] from Alice, server BS does the following steps: (a) Abort if x > BS.${\mathrm{onBal}}_{\mathrm{A}}$. (b) BS.onbal${}_{\mathrm{A}}\leftarrow$ BS.${\mathrm{onBal}}_{\mathrm{A}}$ - x. (c) BS.i${}_{\mathrm{A}}\leftarrow$ BS.${\mathrm{i}}_{\mathrm{A}}$ + 1. (d) Send [DepositConfirmed, x, BS.i${}_{\mathrm{A}},\sigma$] to A, where $\sigma \leftarrow$ Sign([${\mathrm{T}}_{\mathrm{A}}$.pbk, x, BS.${\mathrm{onCounter}}_{\mathrm{A}}$], BS.prk). Upon receiving [DepositConfirmed, x, BS.onCounter${}_{\mathrm{A}},\sigma$] from BS. A invokes T.Deposit(x, BS.onCounter${}_{\mathrm{A}},\sigma$).