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CS 59000-BTS (Hyperledger Questions (PoET :red_flag: (:star: Concepts (K…

- - - - How can this problem be solve? Does it requiring more tech/tools or it needs more adopter to this YAC algorithm? :question:
    - - Step 1: The ordering service shares a proposal to all peers. A proposal is an unsigned block created and shared to peers in the network by the ordering service. It contains a batch of ordered transactions.
      - Step 2: Peers calculate the hash of a verified proposal and sign it. The resulting <Hash, Signature> tuple is called a vote.
      - Step 3: Based on the hashes created in the previous step, each peer computes an ordering list or order of peers. To do this, the ordering function will need to have knowledge of all the peers voting in the network, and is based on the hash of the proposed block. The first peer in the list is called the leader. The leader is responsible for collecting votes from other peers and sending the commit message.
        
        :question: How can voting and hash be used for ordering? Why not timestamps?
        
        Ordering service: Orders transactions into proposals which are sent to peers
      - Step 4: Each peer votes. The leader collects all the votes and determines the supermajority of votes for a certain hash. The leader sends a commit message that contains the votes of the committing block. This response is called a commit.
      - Step 5: After receiving the commit, the peers verify the commit and apply the block to the ledger. At this point, consensus is complete.
      - :question: What are the stateless and stateful transactions?
        
        The main difference between stateless validation and stateful validation is that stateless validation is faster and does not require access to the data on the chain.
    - - Android: https://github.com/hyperledger/iroha-android
        iOS: https://github.com/hyperledger/iroha-ios.
    - - YAC consensus library
        
        Ordering and Consensus
      - Ed25519 digital signature library
      - SHA-3 hashing library
      - Iroha transaction serialization library
      - P2P communication library
      - iOS library
      - Android library
      - JavaScript library
      - Blockchain explorer/data visualization suite.
    - - Tasks: Collects votes from other peers and forwards commit messages to peers
  - - - The following are key benefits of using Hyperledger Composer:
      - Focusing on the problem
      - Develop blockchain application starting from the business requirements.
      - Prototyping
      - Hyperledger Composer provides a smart tool to revise and rearrange model and logic to build simple Proof of Concepts or MVPs.
      - Analytics and privacy
      - Rich queries on the data can be easily set up and performed. Access Control Rules help to preserve a layer of confidentiality for the business operations.
      - Integration to existing systems
      - A REST server exposes your Blockchain to a Web or Mobile Application to be integrated in existing systems.
      - Communication
      - Finally, Hyperledger Composer can be used to enhance the communication between business and technical teams to facilitate prototyping and development of the blockchain application.
    - - Modeling language files (models/*.cto)
        
        To define models for Participants, Assets, Transactions and Events.
      - Transaction logic (lib/*.js)
        
        To implement the logic of the transactions defined.
      - Query file (queries.qry)
        
        To design and enable complex queries on the blockchain data.
      - Access Control file (permissions.acl)
        
        To control visibility and actions on resources.
    - - Buyer
      - Seller
      - Regulator
  - - - Buying a house online with zero-day latency! :tada:
    - - :question: Where does the data stored? Blockchain or local (peers'/mine) database(s)?
    - - Decentralized Identifiers (DIDs) created and controlled by the owning entity
      - The use of DIDs for each relationship, preventing cross-service correlation
      - Peer-to-peer, end-to-end encryption from message creator to receiver
      - Verifiable Credentials (VC) held by their owner and used only when necessary
      - Selective disclosure of VC data - exposing only the data necessary
      - The use of VCs without the need to contact the issuer.
    - - Proactive not reactive; preventative not remedial[3][30][31][32]
      - Privacy as the default setting[3][30][31][32]
      - Privacy embedded into design[3][30][31][32]
      - Full functionality – positive-sum, not zero-sum[3][30][31][32]
      - End-to-end security – full lifecycle protection[3][30][31][32]
      - Visibility and transparency – keep it open[3][30][31][32]
      - Respect for user privacy – keep it user-centric[3][30][31][32]
  - - - Endorsor
      - Orderer
      - Committer
    - - Kafka
      - YAC
      - RBFT
      - PoET
    - - Level DB
  - - - Attack to PoET?
      - How good is the est. of K participants?
      - Can we use any distribution other than exponential?
      - What if Intel SGX is not actually secure?
        
        Then we can have DDoS?
        
        The protocol just doesn't works, and everything is just broken.
    - - Ripple
      - Sawtooth :star:
    - - Deciding who to recording the transactions
      - PBFT consensus of Fabric is just voting until 2/3 of the member agree?
        
        No consensus?
    - - Can be secure hardwares
        
        e.g.: Intel SGX
    - - K-participants [estimation]
      - $$\mu_{local} = K \times \mu_{global}$$
      - $$\lambda_{local} = \frac{1}{\mu_{local}} = \frac{1}{\mu_{global}\times K} = \frac{\lambda_{global}}{K}$$
      - Pick the block that has lower value
      - $$t_i \leftarrow e^{\lambda_{local}}$$ (note that t_i is trusted)
      - Each node pick a random number from exponential distribution.
    - - $$\mu_{local} \times \alpha$$, where $$1 < \alpha < \inf$$
      - S-blocks
      - Question to solve here: What is the expected number of block to be generated by a specific party?
    - - DNS poisoning to prevent other miners to properly work on the protocol
        
        SGX is the one to connect to the protocol, thus we will need to compromise that
      - DDoS
- - - - The right to create channel or consortia are granted by the network builder, and this is the core part for the ACL in Hyperledger Fabric! :red_flag:
      - Channel provides privacy to the members in the channel and maintaining the shared infrastructure with all the consortium at the same time.
      - Including the data transacted on the channel are completely separated from the rest of the network and channels.
    - - Peer nodes holds the copy of the copy of the blockchain ledger.
      - The specific ledger is physically hosted on peer node, but logically hosted on the channel of it.
      - How peers join net work :red_flag:
        
        Peer configuration is an X.509 identity issued by CA of the channel, which associates peer with organization that built the channel. Once the peer is started, it can join channel using the ordered. The orderer will uses the channel configuration to determine this peer’s permission on this channel. (Permission: such as read/write)
      - Types of peers :red_flag:
        
        Committing peers
        
        To help the channel to record validated transactions (appending)
        
        Endorsing peers
        
        Just a peer that has chaincode installed. But it must also have the client application using this chaincode to generate digital signature for the transactions
        
        Static/ Dynamic Lead node
        
        Helping to distribute transactions to committing peers
        
        Anchor peer
        
        inter-organization/channel communication
    - - Public key infrastructure
      - Also called X.509 Certificates, which is an ITU standard for digital certificates.
    - - Just build a smart contract on peer(s) and then connect the client to the peer and the channel
      - All the access patterns for client are going through smart contract first before the client can access the ledger.
      - The installation of the smart contract is assigned by the
    - - Physically hosted by peers
        
        Installed by peers, and can only be accessed by peers
      - Logically hosted by the channel
        
        Instantiating the contract to let everyone in the channel know, but not the program logic details (private code)
  - - - The problem it is solving: deployment
      - Image and Container
        
        Analog to the Class and Object in OOP: The Container of Docker is the instance of an Image, and we have build multiple Container from one Image.
      - Copy-on-write (COW)
        
        求同存异
        
        Only distributed when differences are found
      - Layering to save memory
      - Build and then run, and that's it
      - You can update images by commit and tagging