HFCP Sample Questions & Answers

Committing a chaincode definition requires satisfying the channel's LifecycleEndorsement policy (typically a majority of organizations). If not enough organizations have submitted an 'approveformyorg' transaction for the new definition, the 'commit' transaction will fail validation.

The chaincode lifecycle requires that each new definition committed to a channel must have a sequence number that is exactly one greater than the previously committed sequence number. Failing to increment the sequence number is a common reason for commit failure.

Anchor peers are defined in the channel configuration. To update them on a live network, an administrator must create a channel configuration update transaction. This involves fetching the latest config block, using configtxlator to convert it to JSON, modifying the anchor peer definition, converting it back to a protobuf, and submitting the signed update transaction to the channel.

CouchDB supports rich queries against the JSON data values stored in the world state. To make these queries performant and avoid full database scans, a corresponding index must be created for the fields being queried (in this case, the 'owner' field). The chaincode can then use a GetQueryResult call with a selector to efficiently find all assets for that owner.

This is event checkpointing. The Fabric Gateway client API does not reconnect automatically: after a failure the application must start a new eventing session at the correct start position. A checkpointer (for example checkpointers.file(path)) persists the block number and the last processed transaction ID within that block; passing it as the checkpoint option to getChaincodeEvents() resumes eventing just after the last processed event, with no missed or duplicated events. There is no replay=true option, and neither evaluateTransaction nor a peer buffer setting can recover missed events.

The operations service, which exposes a REST API for health checks and a /metrics endpoint for Prometheus, must be enabled and configured on the components you wish to monitor. This is done within the operations section of the core.yaml file for peers and the orderer.yaml file for orderers.

MVCC (Multi-Version Concurrency Control) is used by Fabric to detect state conflicts. An MVCC_READ_CONFLICT occurs when the version of a key that a transaction read during endorsement does not match the current version of that key in the ledger at commit time. This means another transaction updated the same key in the time between this transaction's endorsement and its commit.

Every chaincode has an implicit, organization-specific private data namespace, _implicit_org_ , that needs no collection definition. Its dissemination policy and endorsement policy are the organization itself, so the data is stored only on that organization's peers and any write to it must be endorsed by that organization. This makes it useful for keeping an organization's own private data or recording its agreement or vote (the v2 chaincode lifecycle uses implicit collections to track approvals). Because memberOnlyRead, memberOnlyWrite and blockToLive cannot be set, client access control must be coded in the chaincode and the data is never purged automatically.

In the Fabric Gateway client API, proposal, transaction and commit-status messages are normally signed with the signing implementation supplied when connecting. When an external party holds the credentials, the signer can be omitted and each message is signed off-line: the application gets the serialized message and its digest (getBytes()/getDigest()), the key holder signs the digest, and the application creates the signed object with gateway.newSignedProposal(), gateway.newSignedTransaction() or gateway.newSignedCommit(). All three are signed by the same client identity. Off-line signing changes where the signature is produced; it is not a way to collect signatures from several approvers. Endorsing peers add their own endorsements, but these never replace the client's signature.

The Blockchain Cryptographic Service Provider (BCCSP) is the component responsible for all cryptographic operations. To configure an HSM, you must modify the peer.BCCSP section in the peer's core.yaml file. You would set the provider to PKCS11 and provide the path to the PKCS#11 library, the label, and the PIN for the HSM slot.

This solution correctly uses a Private Data Collection to ensure only OrgA and OrgB have access to the asset details. The AND('OrgA.member', 'OrgB.member') endorsement policy ensures that any change requires approval from both parties. OrgC, being on the channel but not in the PDC, will see the public transaction with the hash of the private data, allowing it to verify integrity without seeing the private content, thus fulfilling all requirements.