Overview of Interactive Private Smart Contracts Sample Clauses

Overview of Interactive Private Smart Contracts. Private Smart Contract (PSC) execution involves three phases as shown in Figure 2. The first, which we call the freeze phase (a term borrowed from Hawk), is where each partici- pant sends its input coin to the blockchain. The blockchain “freezes” the coins so that they cannot be spent and records them for use later. The second phase is computation. This occurs off-chain and involves the parties running an MPC protocol between them. The third phase is what we call finalization where at least one party must notify the blockchain of the result of the MPC program. There are a set of output coins resulting from smart contract execution (one for each party). The blockchain has to check that the sum of the input coins is equal to the sum of the output coins. Once this is asserted, the blockchain can award the output coin to each party; we call this contract closure1. Fig. 2. How Interactive Private Smart Contracts will Work II. FORMAL DEFINITIONS‌ { ∈ ≤ } We distinguish amounts of currency with a leading “$” (dollar sign) symbol before the associated variable name or literal value to enhance readability. We define the set of valid currency values V as the set of non-negative integers less than a strict upper bound L. More formally, we have that V := $val Z : 0 $val < L . For convenience, we choose L as a power of 2 i.e. we let L = 2A for some positive integer A. × { } → × { } ∪ {⊥}