This repository is a simple implementation of an atomic swap of ratings for rewards assuming a rating system deployed on two blockchains: one to handle the payments and the other handling the ratings.
The high level workflow is the following:
- Carl owns a restaurant and Alice eats there;
- Carl sets Alice's bill to paid with cryptocurrency;
- When Alice pays, Carl grants her a permission to rate his restaurant;
- When she rats Carl's restaurant, she receives a reward (e.g. a small number of ETH).
The idea is to split the system into two blockchains and connect the operations above with atomic cross-chain swaps [Herlihy].
The operations can be split into two exchanges (or swaps):
- Alice exchanges her payment for the permission to rate (Payment-Permission);
- Alice exchanges her rating for a reward (Rating-Reward).
Each exchange can be implemented with Hash Time Locked Contracts (HTLCs).
The smart contracts are in Solidity within a Truffle working environment.
The smart contracts are a re-adaptation of Alessandro Mazzarella's bachelor thesis.
There are 4 type of HTLCs:
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Payment-Permission HTLCs:
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- Usr_Pay_Perm: is the HTLC Alice, the customer or user, deploys to promise her payment towards Carl;
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- Res_Pay_Perm: is the HTLC Carl, the restaurant owner, deploys to promise the permission to rate towards Alice.
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Rating-Reward HTLCs:
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- Usr_Rev_Rew: is the HTLC Alice deploys to promise her rating towards Carl's restaurant;
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- Res_Rev_Rew: is the HTLC Carl deploys to promise the reward toward Alice.
A Rating smart contract collects the permissions and the ratings. To allow the HTLCs to store permissions and ratings, Carl, the Rating's owner, needs to approve the HTLCs.
Simulate two blockchains with two ganache instances: one listening to port 8545 (default) and the other listening to port 7545.
ganache -p 8545
ganache -p 7545
The script test.js shows how to connect to the two ganaches and the operations flow. The script also stores the gas costs of the operations in gasCosts.csv.
[Herlihy] Maurice Herlihy. 2018. Atomic Cross-Chain Swaps. In Proceedings of the 2018 ACM Symposium on Principles of Distributed Computing (PODC '18). Association for Computing Machinery, New York, NY, USA, 245–254. https://doi.org/10.1145/3212734.3212736