Table 2.

Model-based Smart Contracts

Paper	Sources	Product/Objectives	Comments
(Kosba et al. 2016)	2016, IEEE	“Hawk” is a formal smart contract model, where cryptography for the respective functionality is automatically incorporated.	Hawk, a framework for privacy-preserving of data in smart contracts. The performance is evaluated by using a SNARK-friendly implementation in the circuits pour, freeze, compute, and naive. The security level used by the native is 80 bit and the cost incurred in standard cryptographic uses has incurred again equal to the 2 to 2.6 times of native implementations.
(Zhang et al. 2016)	2016, ACM	A formal model satisfying its basic security properties in the Universal Composability (UC) framework with the help of Intel Software Guard Extensions (SGX). It is an Ethereum blockchain-based front-end that supports confidentiality.	Town Crier (TC) is a bridge between smart contracts and existing web sites. The model is validated with three applications: asset digitization (CashSettledPut), flight insurance (FlightIns), and normal trading process (SteamTrade). CashSettledPut shows the best throughput and SteamTrade shows the worst throughput with respect to the number of enclaves on a single machine.
(Juels et al. 2016)	2016, ACM	The Ring of Gyges is a “Criminal Smart Contract (CSM)” model developed to detect criminal activities like murder, arson, etc.	The proposed model is used to maintain law and order in the country due to the immutability and distributed nature of blockchain. The model is tested with three different crime like leakage of secrecy (loss of private information, money, documents, etc.), key theft (loss of private hash key value), and calling card crimes (assassination, assault, murder, sabotage, hijacking, kidnapping, denial-of-service attacks, and terrorist attacks).