MODULE 5: BLOCKCHAIN

1991

Cryptographically linked timestamped document chains

proposed by Haber &

Stornetta — the

conceptual root of

blockchain.

What year

2008

Satoshi Nakamoto

publishes the Bitcoin

whitepaper, “A Peer-

to-Peer Electronic

Cash System,” on a

cryptography mailing

list.

What year

2009

The Bitcoin genesis

block (block 0) is

mined on Jan 3 —

the blockchain goes

live for the first time.

What year

2010

First real-world

Bitcoin transaction:

10,000 BTC for two

pizzas — “Bitcoin

Pizza Day.”

What year

Ethereum mainnet

launches, introducing

general-purpose

smart contracts and

programmable

dApps.

What year

2016-now

Enterprise &

consortium chains,

DeFi, and security-

focused applications

expand blockchain

far beyond currency.

What year

blockchain

is a distributed ledger replicated across many independent nodes. Transactions are grouped into blocks,

cryptographically linked in sequence, and validated through

consensus — with no central authority approving them.

Decentralization

No single controlling party

Transparency

Ledger visible to participants

Cryptographic

security Keys and hashing

protect data

Immutability

Confirmed records resist

tampering

Distributed Ledger Technology

Every participating node holds a full (or partial) copy

of the ledger; updates propagate peer-to-peer and

require network agreement.

▪ Eliminates a single point of failure — compromising

one node does not compromise the record.

▪ Removes reliance on a trusted third party (bank,

registrar, clearinghouse) to validate transactions.

Consensus Mechanism

How independent nodes agree on which transactions are valid — without a central referee.

Proof of work

Miners compete to solve a

computational puzzle; the winner

adds the next block. Used by Bitcoin.

Strong, battle-tested security but

energy-intensive and slower.

Proof of stake

Validators are chosen to propose

blocks in proportion to the

cryptocurrency they stake as

collateral. Used by Ethereum since

2022. ~99.95% less energy than

PoW.

Delagated PoS/BFF Variants

Token holders elect delegates

(DPoS), or a rotating validator

committee reaches Byzantine fault-

tolerant agreement (PBFT,

Tendermint). Faster finality, more

centralization risk.

PoW

___ with the longest-chain rule offers the strongest formal security guarantees studied to date.

Immutability

Each block contains a cryptographic hash of the previous block. Altering any block would require recomputing every block after it, across a majority

of the network — computationally impractical at scale. Tampering breaks the chain and is immediately detectable.

Decentralized Trust

Traditional systems rely on a trusted

intermediary. Blockchain replaces that

intermediary with cryptography and consensus

among mutually distrustful parties — trust

becomes a property of the protocol and network,

not any single institution

Hash

One-way functions (e.g., SHA-256)

that turn any input into a fixed-length

fingerprint. Any change in input

drastically changes the output — the

basis of block linking and tamper-

evidence.

Public Key Cryptography

Each participant holds a private key

(secret, used to sign) and a public

key (shared, used to verify).

Ownership and authorization are

proven without revealing the private

key.

Digital signature

A transaction signed with a private

key can be verified by anyone using

the matching public key — proving

authenticity and preventing forgery or

denial of authorship.

hashing

____ proves data hasn't changed

Signing

_____ proves who authorized it.

Decentralized Identity

Self-sovereign identity lets users hold and

selectively share verified credentials, cutting

reliance on breach-prone central identity

databases

Secure IoT Device Authentication

Devices register and verify identity on-chain

before communicating, reducing spoofing and

unauthorized device access in sensor networks.

Tamper proof audit logs

Immutable, timestamped logs of system or user

events support forensic investigation and non-

repudiation in security incidents

Healthcare record integrity

Patient-controlled, cryptographically verifiable

medical records improve privacy, access

control, and interoperability across providers.

Supply-chain & anti-counterfeiting

Immutable provenance tracking (e.g., IBM Food

Trust) verifies authenticity and detects

tampering across pharmaceutical and goods

supply chains.

Decentralized DNS & PKI

alternatives

Blockchain-based naming and key-distribution

systems (e.g., Namecoin-style designs) reduce

single points of failure in domain and certificate

trust.

Finance

Cross-border settlement, fraud-resistant audit trails,

and cryptographically secured KYC data shared across

institutions without duplicating central databases.

Government

Tamper-proof voting records, land/property registries,

and public credential verification (licenses, diplomas)

that resist forgery.

Critical infrastructure & IoT

Device identity and firmware-update verification for

grids, industrial control systems, and connected sensors

— reducing spoofing and unauthorized firmware

pushes.

Legal & intellectual property

Immutable timestamping of contracts, patents, and

creative works establishes provable prior existence and

non-repudiation.

Formal verification & static analysis

Automated tools such as Slither, MythX, and Echidna

catch flaws before deployment.

Bug bounty programs

HackerOne saw a 147% rise in valid blockchain

vulnerability reports in 2024 alone.

Multi-signature governance

Require multiple approvals for high-value or administrative actions.

Independent audits

Third-party smart contract audits before code goes live on

mainnet.

Defensive coding patterns

Checks-effects-interactions ordering, reentrancy guards,

SafeMath arithmetic.

Diversified consensus

Broader validator/miner distribution raises the cost of a

51% attack.

Data Protection (GDPR Style)

Immutability can conflict with a legal “right to erasure”

— solved via off-chain storage of personal data with

only hashes/pointers on-chain.

Digital asset frameworks

Jurisdictions are formalizing rules for stablecoins,

custody, and exchange operations (e.g., evolving

frameworks like the EU's MiCA and U.S. digital-asset

legislation).

Financial regulation (AML/KYC)

Exchanges and custodians must verify identity and

monitor transactions, even when the underlying ledger

is pseudonymous.

Smart contract liability

Open legal questions remain around who is

accountable when autonomous contract code causes

harm or loss.

Zero-knowledge proofs

Prove a statement is true (identity, solvency, computation)

without revealing the underlying data — already used by

Layer-2 rollups for privacy and scalability

Post quantum cryptography

Quantum computers could eventually break the elliptic-

curve signatures most chains rely on. NIST finalized post-

quantum standards in 2024; networks like Algorand have

already tested quantum-resistant signatures.

Account abstraction & key agility

Letting individual accounts upgrade their signature

scheme (e.g., to post-quantum) without a disruptive

network-wide migration.

Layer-2 scaling with STARKs

Hash-based proof systems (STARKs) avoid the quantum-

vulnerable math of older SNARK designs while scaling

transaction throughput.

Blockchain

offers cryptographically enforced integrity and trust without a central authority.

Its guarantees are strong where they apply — data tamper-evidence, disintermediation —and weak where humans still write the rules: contract code, key custody, and consensus

economics.

Smart Contract

Distributed ledgers enable the coding of simple contracts that will execute when specified conditions are met

Sharing Economy

By enabling peer-to-peer payments, the blockchain opens the door to direct interactions between parties.

Crowd Funding

Blockchains take this to the next level, potentially creating crowd sourced venture capital funds.

Governance

By making vote results fully publicly accessible, distributed database technology could bring full transparency to elections.

Supply Chain Auditing

Blockchains provide an easy way to certify the origin of products. Blockchain timestamping of dates and locations would correspond with product numbers.

File Storage

Decentralizing file storage on the internet brings clear benefits. Distributed data prevents hacked and lost files.

Prediction Market

_____ pay out according to event outcomes. Blockchains are a "wisdom of the crowd" technology that will no doubt find new applications for years.

Intellectual Property

Smart contracts can protect copyright and automate the sale of creative work online. This eliminates the risk of file copying and redistribution.

Internet of Things

Smart contracts can automate remote systems through a combination of software, sensors, and network facilities.

Microgrids

Blockchains enable markets for renewable energy within local areas like neighbourhoods.

Identity Management

Distributed ledgers offer enhanced methods to prove who you are. Having a secure, digitized identity will be important as online services continue to evolve.

AML and KYC

Improving anti-money laundering and know your customer practices can have huge potential. Cross-institution client verification and stronger analysis is possible with blockchain.

Private Data Management

Users will have the ability to manage and sell their online activity profiles in small, fractured amounts if they see fit.

Land Title Registry

Publically accessible legers can make all types of record keeping more efficient. Property titles are susceptible to fraud, and can be secured on chain.

Stock Trading

When peer-to-peer trade confirmations become instant, intermediaries like auditors and custodians get removed from the process.

Blockgeeks