• Underlying technology for cryptocurrencies like Bitcoin
• Distributed Ledger Technology that is applicable to many sectors
• Combination of existing technologies like peer-to-peer networks and cryptography
What is Blockchain?
• Ledgers have been used for centuries to
capture various types of transactions.
• Have certain issues:
• Centralized – one master copy
• Susceptible to tampering
• Require intermediaries
Distributed Ledger Technology
• A Distributed Ledger Technology System…
• enables a network of independent
participants to establish consensus around…
• the authoritative ordering of
• These records are made persistent by
replicating the data across multiple nodes and
• tamper evident by linking them to
• establishing an authoritative record in each
A Network of Nodes
• A node is set up on each of the computers
participating in the network.
• The node system operates via a peer-to-peer
network (aka, P2P).
• The network can be vast and widely geographically
distributed, but the nodes do need to be able to
communicate with each other.
• A node is typically directly connected to some, but
not all, of the other nodes.
• When one node sends a transaction to its peer
nodes, those peers then forward that transaction to
other peers, who in turn forward it to yet still others,
thereby reaching the entire network of nodes in
A Shared Ledger
• The shared ledger is the data component that
resides in system.
• The nodes in the network update the data in the
ledger and the consensus algorithm manages the
system to assure that only one true version of the
• The most common method for implementing a
shared ledger is through the use of a blockchain.
• As transactional data is received, it is grouped
together into units, called blocks.
• Each block is then verified and appended to the
previous block, thereby creating a chain of blocks.
• As a block is copied to the chain, it is distributed to
all the nodes in the network, thus keeping the copies
of the blockchain in harmony.
A Consensus Algorithm
• The consensus algorithm sets the rules
for the system that determine how the
nodes will arrive at a single view of the
• Different DLTs use different approaches
• All consensus algorithms are there to
make sure that each node is qualified to
write their data to the ledger and to
assure there is a consistent and
• A smart contract is a digitized
contract that is stored on the
• Contains programming logic
that can automatically
execute the terms of the
• Smart contracts can be
looked at as the business
logic layer of the DLT stack
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