This repo is no longer in use. It contains historical information about Atomic Crosschain Transactions for Ethereum Private Sidechains. Please see https://github.com/ConsenSys/gpact for information about the General Purpose Atomic Crosschain Transaction protocol.

NOTE: The version of log4j in this repo has a known vulnerability. If you choose to use the code in this repo, you will need to upgrade log4j.

Atomic Crosschain Transaction Sample Code

The repository contains sample code to demonstrate how to use Sidechains and Atomic Crosschain Transaction technology.

Atomic Crosschain Transactions are explained in our white paper [https://github.com/PegaSysEng/sidechains-samples/blob/master/AtomicCrosschainTransactions-WhitePaper.pdf] and in this YouTube video [https://www.youtube.com/watch?v=MrrUHC-d6lc].

The samples in this repo should be used in conjunction with [https://github.com/PegaSysEng/sidechains-besu], a modified version of Hyperledger Besu and [https://github.com/PegaSysEng/sidechains-web3j], a modified version of Web3J. To start:

--- install JDK8, JDK 11, node version 10 ---
--- then:                                 ---
mkdir crosschain
git clone https://github.com/PegaSysEng/sidechains-samples.git
git clone https://github.com/PegaSysEng/sidechains-web3j.git
git clone https://github.com/PegaSysEng/sidechains-besu.git
--- set the PATH to point to JDK 8        ---
--- then:                                  ---
cd sidechains-web3j
./gradlew installDist
--- set the PATH to point to JDK 11       ---
--- then:                                  ---
cd ../sidechains-besu
./gradlew installDist
cd ../sidechains-samples
scripts/create_chain.js 11 1 
scripts/create_chain.js 22 1
scripts/create_chain.js 33 1

To test the sample code:

./gradlew integrationTest

To run any of the samples:

1. Run three Hyperledger Besu nodes, one node per blockchain. The simplest way to do this is run the command: scripts/run_multichain.sh. Alternatively, using three command windows execute the commands: scripts/run_node.sh 11, scripts/run_node.sh 22 and, scripts/run_node.sh 33.
2. Before the first time the samples are run, configure the Multichain Node:

   ./gradlew build
   cd crosschain/multichain/build/distributions
   tar xvf tar xvf crosschain-multichain.tar
   cd crosschain-multichain/bin
   sh crosschain-multichain config auto
   cd ../../../../../..
   

3. Execute any of the samples either in an IDE of by running the binary in a similar way to how the Multichain Manager is run in the code box above.

The samples:

• crosschain/atomic-swap-ether: Atomic Swap of Ether between blockchains.
• crosschian/hotel-train: Allows a hotel room and a train seat to be booked and paid for.
• crosschain/multichain-manager: Multichain Node management tool.
• crosschain/simple: Samples showing how to do specific operations.
• crosschain/three-chains-six-contracts: Crosschain transaction example containing a complex call graph that includes subordinate transactions and subordinate views.

Other directories:

• common: Common code used across many samples. This includes the default simple set-up of the Crosschain Coordination Contract.
• crosschain/common-solidity: Crosschain Coordination Contract Truffle project and other pieces of Solidity code used across many samples related to crosschain.
• testall: Allows some key code paths of each of the samples to be run as a JUnit test.
• scripts: Ancillary scripts to help create a set of nodes in a blockchain and run them.

Limitations of the PoC:

• The Sidechains-Besu repo and Sidechains-Web3J repo were forked from their respective upstream repositories in September 2019, and as such do not incorporate the latest enhancements and defect fixes.
• This technology has been created as a PoC. The Atomic Crosschain Transaction technology has some level of test coverage, though not as much as would be expected with production software.
• Only one node per blockchain is currently supported. The DevP2P sub-protocol to facilitate distributed threshold key generation and distributed signing needs to be completed to allow for multiple nodes per blockchain.
• The signature verification of Subordinate View Result messages and Subordinate Transaction Ready messages has been disabled. This is a result of the current (Java) implementation of the ECC BLS pairing code taking a long time to execute, resulting in the test system timing out. The current implementation needs to be replaced with a faster implementation.
• The on-chain signature verification of Start, Commit and Ignore messages has been disabled. This is due to some inconsistencies that are yet to be resolved in the expected and actual to-be-signed data. Analysis has shown this is related to a data encoding issue. The on-chain signature verification code itself is working.