Permissioned blockchains

Question 1

Hyperledger architecture

Answer 1

Orderers: Create blocks
Peers/Endorser: execute transactions and execute smart contracts
orgs: every organisation possesses its own nodes
id management: each org has own ca to manage ids
clients: interact with blockchain

Question 2

Queries and Invokes

Answer 2

Queries only read state of blockchain invokes write to blockchain

Question 3

Invoke flow

Answer 3

1.Invoke is sent to endorsers
2. Endorsers simulate execution locally and endorse it by signing it
3. Client collects endorsements and creates transaction
4. Endorsed transaction is then sent to the orderers who create a block
5. Finally transaction is sent back to peers so they can update state
Transaction aborted if:
readset intersects with previous transactions write set
writeset intersects with previous transactions write set

Question 4

Execute then order

Answer 4

Transaction are first executed and then ordered and applied => can be conflicting
problems:
increased latency, valid transaction may be reject, client doesnt know if accepted or not
advantages:
smart contracts can be partially non deterministic, smart contracts dont affect blockchain, miners can order faster

Question 5

endorsement policy

Answer 5

defines which endorsers need to be endorsing transaction to be valid can be done using AND, OR