This smart contract demonstrates an 'Atomic cross-chain swap between different blockchain networks'. The blockchains needs to support 'secret lock' and 'secret proof' functionalities. It's possible with Ethereum, Bitcoin, NEM, NEO and several other products. This smart contract is based on the NEM cross chain swap functionality.

• Nemtech.
• Bitcoin Atomic cross-chain trading

However if it's real 'Atomic' is valid point to discuss. But both parties have a strong incentive to fullfill the rules

Lets say Alice wants to convert Ether to NEM:XEM and Bob NEM:XEM to Ether.

Hint: The wording in this Ethereum smart contract is a bit different as in the NEM documentation. In my opinion NEM naming is confusing. Especial in NEM secret represents a hash and is not the real secret.

Steps:

• Both agree on an exchange rate.
• Both exchange their addresses to receive the funds.
• Alice creates a secret and the hash of it.
• Alice writes to the Ethereum smart contract secretLock(uint256 _lockTimeSec, bytes32 _hash, address _recipient) and adds the agreed amount of Ether.
• Alice submits the hash to Bob.
• Bob is now able to validate/audit the 'secret lock' in the Ethereum smart contract.
• Bob will now create a 'secret lock transaction' in NEM SecretLockTransaction.create(Deadline.create(), new Mosaic(new MosaicId('nem:xem'), exchangeValue), lockTime, HashType.SHA256, secret, Alice.address, NetworkType.MIJIN);.
• Alice gets notified and can validate/audit the NEM secret lock.
• Alice will then call on the NEM network a 'secret proof transaction'. SecretProofTransaction.create( Deadline.create(), HashType.SHA256, hash, proof, NetworkType.MAIN_NET);.
• So Alice will get the XEM:NEM and for her the swap was successful.
• Bob gets notified by the NEMs secret proof transaction. As it is a public blockchain, Bob sees the proof the real secret.
• Bob then creates an Ethereum transaction to the smart contract. secretProof(bytes32 _hash, bytes _proof). So Bob will receive the Ether.

Web3 version 1.x is installed with NPM. Also Truffle comes with Web3 0.2x. The API of these Web3 are not always compatible.

• Web3 version 1.x
• Web3 version 0.2x.x