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*System
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* Blockchain
A collection of interacting/interrelated entities structured as a whole
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# Organized for a common purpose
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• Blockchains are distributed digital ledgers of cryptographically signed transactions that are grouped into “blocks”
# Entities may include
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# Human
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• Each block is “cryptographically” linked to the previous one after validation and undergoing a “consensus” decision
# Machines
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# Procedures for different functions
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• As new blocks are added, older blocks become more difficult to modify
# Interfaces to the environment (input/output)
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# A system stays in some “state” at any given time
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• New blocks are replicated across all copies of the ledger within the network, and any conflicts are resolved automatically using established rules
# Off duty. Under maintenance/update
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# Operational (hopefully correctly as designed)
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* First Blockchain
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• Bitcoin is the world’s premier blockchain
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• Launched in 2009 by an anonymous person (or a group of persons) known by the name of Satoshi Nakamoto
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• Suspiciously around the time of the Subprime crisis
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• First successful peer-to-peer electronic cash system
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• Bitcoin illustrates how we use blockchain to maintain a history of valid transactions that are tamper-resistant, without any effort from central authority
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*Centralized Systems
 
*Centralized Systems
 
# Homogeneous
 
# Homogeneous

Version du 26 mai 2022 à 19:44


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Définition écrite


  • First Blockchain

• Bitcoin is the world’s premier blockchain

• Launched in 2009 by an anonymous person (or a group of persons) known by the name of Satoshi Nakamoto

• Suspiciously around the time of the Subprime crisis

• First successful peer-to-peer electronic cash system

• Bitcoin illustrates how we use blockchain to maintain a history of valid transactions that are tamper-resistant, without any effort from central authority

  • Centralized Systems
  1. Homogeneous
  2. Easier to design, operate, and maintain
  3. Single point of control & authority
  4. Multiple users share same set of resources
  5. Single point of failure (- Honest, - Malicious)
  • Distributed Systems
  1. A group of independent systems (nodes) working together for a purpose
  2. Connected & communicate to each other via a network
  3. Each operates concurrently
  4. Can continue correct operations even if some nodes fail

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  • Benefits and Challenges

• Performance

• Scalability

• Redundancy (for fault-tolerance)

• How to ensure consistency among nodes of a distributed system?

• Even if some aren’t reliable nor honest?

• Trust without trust?

• Requires a way to reach “consensus”


  • Example: Database Systems

• For a centralized database system, one central entity handles all requests and data processing

• Data updates simple and quick

• Cheaper to manage and maintain

• Performance bottleneck under high concurrent requests

• Single point of failure


  • Distributed Database System

• A group of databases cooperating together to provide single data view to users

• Fault-tolerant

• Handle more concurrent load

• Requires “trust” among nodes (• Not a problem if owned by a single enterprise, • For nodes not fully trusting each other, a “consensus” protocol is required to keep a consistent view of data)


  • Distributed Ledger Technology (DLT)

• A type of distributed database system

• Immutable, append-only database of transactions (for example, exchanges of assets or data)

• Ledgers are replicated, synchronized and shared across all nodes in the distributed, peer-to-peer network

• Nodes reach consensus on transaction updates to its own copy of ledger, thus maintaining consistent ledger state

• Via consensus protocol, this is achievable without central authority or trusted 3rd party mediator


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