Introduction to Blockchain Technologies Sarah Azouvi(University College London)

1Privacy International Forum - 19/10/2017

Outline

OutlineHow it works

OutlineHow it works

Privacy?

OutlineHow it works

Privacy?

New applications

Bitcoin

•Bitcoin: decentralised cryptocurrency

•No central authority, no banks, no government,no censorship, no international fees

•Removes the need for a trusted third party

How does it work?

How does it work?

How does it work?pkB

pkA

How does it work?

tx(pkA pkB)

pkBpkA

How does it work?

tx(pkA pkB)

pkBpkA

How does it work?

tx(pkA pkB)

pkBpkA

• Append-only •Transparent •Pseudonyms

How does it work?

tx(pkA pkB)

pkBpkA

• Append-only •Transparent •Pseudonyms

How does it work?tx(pkA pkB)

tx(pkA pkA)

?

How does it work?Proof of work

How does it work?Proof of work

How does it work?Proof of work

tx(pkA pkB)

tx(pkC pkD)

tx(pkE pkF)

Previous hash

How does it work?

How does it work?

How does it work?

How does it work?

How does it work?Proof of work

How does it work?Proof of work

Longest chain wins

Why does it work?

Why does it work?

=

Why does it work?

=

What does it guarantee?

•A network of peers that do not trust each other

agree on a set of transactions

•Auditability

•Immutability *

What it does not guarantee

What it does not guarantee

•Privacy

What it does not guarantee

•Privacy

•Solve every problem

Privacy

Privacy

•Transparent

•Transactions are linked

•Traceable!

Privacy

•Transparent

•Transactions are linked

•Traceable!

Privacy

pkA pkB

pkBpkC

pkD

pkD

pkEpkF

Privacy• Solution: mixing service

pkA

pkB

pkC

pkD

pkE

pkF

Privacy• Solution: mixing service

pkA

pkB

pkC

pkD

pkE

pkF

Privacy• Solution: mixing service

pkA

pkB

pkC

pkD

pkE

pkF

• New currency: Zcash (ZKP), Monero (ring signatures)

Extensions

Extensions

• Ethereum

Extensions

• Ethereum

• Identity management system

Extensions

• Ethereum

• Identity management system

• Permissioned blockchains, no currencies

Extensions

• Ethereum

• Identity management system

• Permissioned blockchains, no currencies

• Privacy preserving blockchains

Extensions

• Ethereum

• Identity management system

• Permissioned blockchains, no currencies

• Privacy preserving blockchains

• Many others decentralised applications!

Ethereum

Ethereum

EthereumSmart Contract

Ethereum

Smart Contract

tx(pkB smart contract )

Ethereum

• ICO: Decentralised Kick-starter

Ethereum

• ICO: Decentralised Kick-starter

Identity Management

Identity Management

• Control over your data

• Standardise identity management

• Less complex

Identity Management

Identity Management

Identity Management

Identity Management

Industry application

Industry application

Industry application

Industry application

Research •Privacy

•Sustainability

•Scalability

•New applications: decentralized versions of identity management, DNS and public-key infrastructures, notary publics, and file storage

•Usability

Questions ?