I did not find a good tutorial or article answering this question so far, maybe you can help. What I want to do is the following:
Peer A in Org 1 calls chaincode, this chaincode has access to data only available in Org 2 and Peer A never gets access to the full information.
I know that Hyperledger Fabric supports private channels and private data, is it possible to achieve this requirement? If yes can you point me in the right direction to do this?
Yes, it is possible. below are the steps to accomplish. By using private data, you can accomplish your requirements, but little work needed. you an also follow the fabric documentation, i have provided the links here.
The client application submits a proposal request to invoke a chaincode function (reading or writing private data) to endorsing peers which are part of authorized organizations of the collection. The private data, or data used to generate private data in chaincode, is sent in a transient field of the proposal.
The endorsing peers simulate the transaction and store the private data in a transient data store (a temporary storage local to the peer). They distribute the private data, based on the collection policy, to authorized peers via gossip.
The endorsing peer sends the proposal response back to the client with public data, including a hash of the private data key and value. No private data is sent back to the client.
Check this for endorsement: https://hyperledger-fabric.readthedocs.io/en/release-1.4/private-data-arch.html#endorsement
The client application submits the transaction to the ordering service (with hashes of the private data) which gets distributed into blocks as normal. The block with the hashed values is distributed to all the peers. In this way, all peers on the channel can validate transactions with the hashes of the private data in a consistent way, without knowing the actual private data(This is what you need to accomplish).
At block-committal time, authorized peers use the collection policy to determine if they are authorized to have access to the private data(For reading the block data). If they do, they will first check their local transient data store to determine if they have already received the private data at chaincode endorsement time. If not, they will attempt to pull the private data from another peer. Then they will validate the private data against the hashes in the public block and commit the transaction and the block. Upon validation/commit, the private data is moved to their copy of the private state database and private writeset storage. The private data is then deleted from the transient data store.
Resources: https://hyperledger-fabric.readthedocs.io/en/release-1.4/private-data/private-data.html
