Block signing

The Ocean platform incorporates a client/daemon that is installed and run on infrastructure controlled by the issuer to validate and sign blocks on an Ocean sidechain via a fault tolerant multiparty protocol (referred to as Federated block signing and the nodes with block-signing permissions as The Federation). The block signing permissions are defined by the public keys in the M-of-N multisig blocksigning script which is specified in the Ocean sidechain configuration (signblockscript). Each federation signing node coordinates with the other federation nodes to produce valid blocks and combining M signatures on a valid block extending the blockchain over a specified block creation interval. In addition to block creation and signing, the federation client can perform token reissuance operations with the same fault-tolerance properties enabling secure and verifiable inflation of assets according to a specified schedule.


Illustration of a federation of 5 signing nodes, where 3 signing keys are required to produce a valid block to extend the sidechain.


The federated block-signing daemon is a pure Python application and can be downloaded from the CommerceBlock Github here.

  1. pip3 install -r requirements.txt
  2. python3 build && python3 install
  3. For the demo run ./run_demo or python3 -m demo

#. For the federation run ./run_federation or python3 -m federation and provide the following arguments: .. code-block:: bash

–rpcconnect $HOST –rpocport $PORT –rpcuser $USER –rpcpass $PASS –id $NODE_ID –msgtype $MSG_TYPE –nodes $NODES_LIST

Federation arguments:

  • --rpconnect: rpc host of Ocean node
  • --rpcport: rpc port of Ocean node
  • --rpcuser: rpc username
  • --rpcpassword: rpc password
  • --id: federation node id
  • –msg_type: Messenger type used. Possible values: ‘kafka’, ‘zmq’ (optional, default=’kafka’)
  • --nodes: List of node ip/domain names for zmq only
  • --hsm: Flag to enable signing with HSM
  • --inflationrate: Inflation rate
  • --inflationperiod: Inflation period (in minutes)
  • --inflationaddress: Address for inflation payments
  • --reissuancescript: Reissuance token script
  • --reissuanceprivkey: Reissuance private key

Example use:

  • zmq:
  • kafka: python3 -m federation --rpconnect --rpcport 18443 --rpcuser user --rpcpass pass --id 1 (check - defaults to 5 nodes)

Hardware Security Modules

The application has full integration for Hardware Security Modules (HSMs) that support the PKCS11 interface, for block-signing operations and key management.


Assuming HSM and pkcs11 libraries setup and all config/secrets files are in place run:

docker build --build-arg user_pin=$USER_PIN --build-arg key_label=$KEY_LABEL -f Dockerfile.hsm.init .

This will generate a multisig script that should be used as the signblockarg in the ocean sidechain.


To build the federation container with hsm signing run:

docker build --build-arg user_pin=$USER_PIN --build-arg key_label=$KEY_LABEL -f Dockerfile.hsm .

Inside this container federation can be initiated by:

Inflating assets

The federation nodes can be used to reissue issued assets according to a fixed inflation schedule. This is enabled by setting the --inflationrate argument to a non zero value. The assets are then reissued every --inflationperiod blocks, and to the specified address. The reissuance tokens must be paid to the P2SH address of the supplied multisig script (--reissuancescript). The corresponding private key for the signing node (for the reissuance script) is supplied as --reissuanceprivkey. If inflation is enabled, the -rescan=1 and -recordinflation=1 flags must be set in the signing node ocean.conf file.

Federation protocol demo

A demonstration of protocols used by the Ocean network, including federated signing and asset issuance.


./scripts/ python3 -m demo

Running Kafka

  • Install kafka

    brew install kafka

  • Add bin path to PATH in bash profile

    export PATH="$PATH:/usr/local/Cellar/kafka/1.1.0/bin/"

  • Different services

    • brew services start kafka
    • brew services stop kafka
    • kafka-topics --zookeeper localhost:2181 --delete --topic new-block


Generate multisig script and keys using the MultiSig class (M out of N).

Federated Signing

Implement federation signing using the BlockSigning class. Federation signing uses a Kafka broker. Nodes take turns proposing / signing blocks. One node will generate a new block hex and send it to a topic marked as ‘new-block’ in the Kafka broker. The rest of the nodes will fetch this and sign it, sending their signature to a topic marked as ‘new-sigX’, where X is the node id. The node that generated the block will collect the signatures, combine them and submit the block.

Asset Issuance

Issue assets and generate transactions with these assets using the AssetIssuance class.