foodchain

Example Blockchain to track from farm to store.

Building on top of the Hyperledger Fabric project.

There are two kinds of blockchains out there:

1. Public Blockchains (e.g. Bitcoin, Ethereum)
2. Private/Permissioned Blockchains (e.g. Hyperledger)

Issues with public blockchains

• The blocks in Bitcoin and Ethereum have a storage issue. Bitcoin has a little over 1MB of space per block which is simply not enough to run the kind of transactions and store the kind of data that enterprises require.
• Bitcoin can barely manage 7-8 transactions per second (tps). The block confirmation time is 10 mins which just adds to the latency. Enterprise use cases need to deal with millions of transactions per day with near 0 latency.
• Public blockchains, especially the ones that follow the proof-of-work protocol like Bitcoin require an immense amount of computational power to solve hard puzzles.

Private/Permissioned Blockchains

In order to reach those levels of tps, blockchains need to adopt an architectural approach which:

• Efficiently compartmentalises different tasks.
• Uses asynchronous flows.
• Uses faster consensus protocols.
• Utilises parallelisation
• Executes itself in optimised environments.

Other challenges

1. Storing data

   Most blockchains use a transaction-based data model: Sender, Value, Receiver.

   • Some blockchains offer the possibility to append data to a transaction within their protocols, while others do not.
   • Encode the data into the receiving address.
     • Tiny (Kbs) address size
     • Cost. (When storing data on the blockchain, most often we do pay a base price for the transaction itself plus an amount per byte we want to store. If smart contracts are involved, we also pay for the execution time of the smart contract.)
     • Every member can see the data unless hashed or encrypted.
     • General Data Protection Regulation (GDPR) - data is immutable.
     • No query facility.
   • Split data up - Cost!
   • Store a hash (tamper proof) to a record on another database.
     • Trade-offs for decentralisation and transparency
   • Store hash and subset of data - hybrid approach
   • Use a distributed database for off-chain storage

2. Performance

   Alternatives to proof-of-work:

   • Proof-of-stake
     • Byzantine Fault Tolerance
     • Delegated Proof of Stake

Economic Sets

The purpose of a consensus algorithm, in general, is to allow for the secure updating of a state according to some specific state transition rules, where the right to perform the state transitions is distributed among some economic set. An economic set is a set of users which can be given the right to collectively perform transitions via some algorithm, and the important property that the economic set used for consensus needs to have is that it must be securely decentralized - meaning that no single actor, or colluding set of actors, can take up the majority of the set, even if the actor has a fairly large amount of capital and financial incentive. So far, we know of three securely decentralized economic sets, and each economic set corresponds to a set of consensus algorithms:

• Owners of computing power: standard proof of work, or TaPoW (Transaction as Proof of Work). Note that this comes in specialized hardware, and (hopefully) general-purpose hardware variants.
• Stakeholders: all of the many variants of proof of stake
• A user's social network: Ripple/Stellar-style consensus

See Proof of State, Ethereum Blog.

Running the example

(The following commands are all assumed to run from the root directory each time.)

1. Create Network.

   cd network
   ./start.sh
   

   The following docker services will start:

   • hyperledger/fabric-peer
   • hyperledger/fabric-orderer
   • hyperledger/fabric-couchdb
   • hyperledger/fabric-ca

   These containers all form a docker network called net_basic. You can view the network with the docker network command:

   docker network inspect net_basic
   

2. Pretend we're the Farmer.

   • Open a new terminal window to monitor the system

     cd organization/farmer/configuration/cli
     ./monitordocker.sh net_basic
     

   • A Farmer administrator interacts with the network via a docker container. Let’s start a MagnetoCorp-specific docker container for the administrator using the docker-compose command:

     cd organization/farmer/configuration/cli
     docker-compose -f docker-compose.yml up -d cliFarmer
     

   • The Farmer administrator will use the command line in the cliFarmer container to interact with the system.

3. Install Smart Contract.

   • Before trackcontract can be invoked by applications, it must be installed onto the appropriate peer nodes.

     docker exec cliFarmer peer chaincode install -n trackcontract -v 0 -p /opt/gopath/src/github.com/contract -l node
     

4. Instantiate Contract.

   docker exec cliFarmer peer chaincode instantiate -n trackcontract -v 0 -l node -c '{"Args":["org.example.track:instantiate"]}' -C mychannel -P "AND ('Org1MSP.member')"
   

   One of the most important parameters on instantiate is -P. It specifies the endorsement policy for trackcontract, describing the set of organizations that must endorse (execute and sign) a transaction before it can be determined as valid. All transactions, whether valid or invalid, will be recorded on the ledger blockchain, but only valid transactions will update the world state.

   Notice that the resulting container is named dev-peer0.org1.example.com-trackcontract-0-... to indicate which peer started it, and the fact that it’s running trackcontract version 0.

5. Create a Track.

   cd organization/farmer/application/
   npm install
   

   First, we must add identity information to Farmer's admin user's wallet.

   node addToWallet.js
   ls ../identity/user/isabella/wallet/[email protected]
   

   Notice:

   • a private key c75bd6911a...-priv used to sign transactions on the admin user’s behalf, but not distributed outside of her immediate control.
   • a public key c75bd6911a...-pub which is cryptographically linked to the admin user’s private key. This is wholly contained within Isabella’s X.509 certificate.
   • a certificate [email protected] which contains the admin user’s public key and other X.509 attributes added by the Certificate Authority at certificate creation. This certificate is distributed to the network so that different actors at different times can cryptographically verify information created by the admin user’s private key.

   Finally, create the track.

   node create.js
   

6. Now, pretend we're the Supplier.

   cd organization/supplier/configuration/cli/
   docker-compose -f docker-compose.yml up -d cliSupplier
   

7. Receive the goods.

   cd organization/supplier/application/
   npm install
   

   Add identity information to Supplier's admin user's wallet.

   node addToWallet.js
   

   Finally, receive the goods and take ownership of the Track.

   node receive.js
   

Shutdown and cleanup example

1. Switch to terminal running monitordocker.sh and Ctrl-C.

2. Switch back and stop the logspout container and peer containers.

   docker stop logspout
   docker stop cliSupplier
   docker stop cliFarmer
   

3. Stop and teardown network.

   cd network
   ./stop.sh
   ./teardown.sh