What Are Private Data Collections?
(Hyperledger Fabric v1.4.7) Private data collections specify subsets of organizations that endorse, commit, or query private data on the channel.
Use private data collections in cases where you want a group of organizations on the channel to share data and to prevent the other organizations on the channel from seeing the data. Private data is distributed peer to peer and not by blocks, so the transaction data is kept confidential from the ordering service. Collections help you reduce the number of channels and their required maintenance on your network.
- The private data that you specify in your private data collection definition. Private data is sent with the gossip protocol from peer to peer within the organizations that you specify in your policy. Private data is stored in a private database on the peer. The ordering service isn't used and can't see the private data.
- A hash of the data, which is endorsed, ordered, and written to each peer on the channel. This hash is evidence of the transaction and can be used for audit purposes.
When you instantiate a chaincode, you can associate it with one or more private data collections. Also when you instantiate a chaincode, you should specify a transient map to pass the private data from the client to the peers for endorsement. The collection definition specifies who can persist data, how many peers the data is distributed to, how many peers are required to disseminate the private data, and how long the private data is persisted in the private database.