Blockchains: Science and Applications · Blockchain Technology: Applications Payment Systems Crypto-currencies such as Bitcoin and Ethereum Payment settlement IOweYou credit networks

Aniket Kate Purdue University

Blockchains: Science and Applications Building the Internet of Value

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Intel Tech Talk, CERIAS, 2016

Research Overview

✦ Cryptocurrencies and Credit Networks [NDSS '17] [PETS '16] [CCS '15] [NDSS '15] [ESORICS '14]

✦ Anonymous Communication Networks [NDSS '17] [ESORICS '16] [ACNS '15 ’14] [CCS '14] [CSF '13 '12] [WPES '12] [TISSec '10] [FC '10] [PETS ’07]

✦ Accountability and Transparency Enhancing Technologies [TDSC '16] [COSN ’15]

✦ Longitudinal Privacy and Right to Delete/Conceal [IC '17] [SOUPS' 16]

✦ Inactive Projects ✦ Privacy-Preserving Web Analytics

[ACSAC '14] [Oakland '12] ✦ Multi-party Computation and Threshold Cryptography

[PODC '14 '12] [CT-RSA '13] [ASIACRYPT '11 ’10] [SCN '10] [ICDCS '09]

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Ever Changing Landscape of Communication

Local Global2000-2010

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Local Global2000-2010

3


Local Global

Centralized

2000-2010

3


Local Global

Centralized

2000-2010

3

2010 onwards


Local Global

Centralized

Decentralized/ Distributed

2000-2010

3

2010 onwards


Local Global

Centralized


2000-2010

3

2010 onwards


Local Global

Centralized


2000-2010

3

2010 onwards

Blockchain for Everything!


Local Global

Centralized


2000-2010

Crypto-currencies may not survive,

but the concept of distributed

ledger/blockchain is here to stay

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2010 onwards


Blockchain can change ... well everything

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Source: CB Insights

Blockchains can change a lot of things

5Source: http://startupmanagement.org/blog

http://startupmanagement.org/blog

What is Money/Currency?

✦ Money can be anything that can serve as a

✦ store of value, which means people can save it and use it later;

✦ unit of account, i.e., it provides a common base for prices; or

✦ medium of exchange, something that people can use to buy and sell from one another.

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What is Money/Currency?

✦ Money can be anything that can serve as a

✦ store of value, which means people can save it and use it later;

✦ unit of account, i.e., it provides a common base for prices; or

✦ medium of exchange, something that people can use to buy and sell from one another.

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What is Money/Currency!

✦ Interesting example: Stone money on the Yap island

✦ Being too large to move, buying an item with these stones is as easy as saying it now belong to the seller

✦ As long as the transaction is recorded in the (oral history!), it will now be owned by the seller

✦ No physical movement of the stone is required!

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Money to the island of Yap

Bitcoin/Blockchain Basics

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Bitcoin TransactionInput

AddressesOutput

AddressesA: B70.345 B': B1

σA

A’: 69.345

sk: signing keyvk: verification key

A: Bitcoin AddressA = Hash(vk)

sk


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AddressesOutput


σA

A’: 69.345



sk


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AddressesOutput


σA

A’: 69.345



public list of transactions or Blockchain

sk

Our Research Thrusts

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Blockchain Technology


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Scalability

Privacy

Science


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Scalability

Privacy

Science

Smart Contracts

Applications

Core Bitcoin Technology: Blockchains

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✦ Blockchain -An asset database that aggregates transactions in blocks, and

these blocks are appended to a chain of existing blocks

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✦ Replications - The blockchain is shared across a global network, such that all

participants can have their own identical copy of the ledger

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✦ Use digital signatures - to control who can do what within the shared ledger

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✦ Use digital signatures - to control who can do what within the shared ledger

✦ Use a consensus mechanism - ensuring that only asset owner cannot use/spend their assets twice

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Blockchain Technology: Applications

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✦ Payment Systems ✦ Crypto-currencies such as Bitcoin and

Ethereum ✦ Payment settlement IOweYou credit

networks such as Ripple and Stellar ✦ Developing the Internet of Value

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✦ Identity Management

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✦ Identity Management

✦ Supply Chain Management ✦ Track Diamonds, food, Goods

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Applications: Smart Contracts

Bitcoin Smart Contracts

✦ Self executing scripts/programs that directly control the transfer of currencies/assets between parties under certain conditions

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Self-Imposable Trustless

Faster Cheaper


✦ Self executing scripts/programs that directly control the transfer of currencies/assets between parties under certain conditions

✦ Example Contracts: ✦ Assurance contracts/crowd funding ✦ Fair exchanges and lotteries ✦ Non-equivocation contracts [CCS ’15]

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Faster Cheaper

Our Application: Non-Disclosure Agreements

✦ Non-Disclosure Agreement—NDA ✦ A legal contract between two parties that outlines confidential material

that the parties wish to share with one another

✦ Also known as ✦ confidentiality agreement (CA), ✦ confidential disclosure agreement (CDA), ✦ proprietary information agreement (PIA), etc…

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✦ Extremely common across industry, and often breached! ✦ Latest Example:

Scorpene submarine data leak from French manufacturer DCNS

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✦ Extremely common across industry, and often breached! ✦ Latest Example:

Scorpene submarine data leak from French manufacturer DCNS

✦ How to enforce the NDA? ✦ Use some trusted third party/ arbitrator

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Non-Disclosure Agreement (NDA): Today

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Non-Disclosure Agreement (NDA): Today

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Expensive and Time consuming

Process

Our Solution based on Smart Contract

✦ NDA time-locked deposit ✦ Aim: Provide a receiver of a confidential

document with a primary incentive to maintain non-disclosure

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✦ The sender and the receiver create a smart contract, ✦ where the receiver puts money in a time-lock deposit such that

- the deposit contract includes private/secret keys from both parties

✦ After the time out, the deposit money returns to the receiver

✦ However, if the sender obtain the secret key for the receiver, it can withdraw the deposit money any time earlier

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✦ The sender and the receiver create a smart contract, ✦ where the receiver puts money in a time-lock deposit such that

- the deposit contract includes private/secret keys from both parties

✦ After the time out, the deposit money returns to the receiver

✦ However, if the sender obtain the secret key for the receiver, it can withdraw the deposit money any time earlier

✦ We secure and privately embed the secret key in documents using oblivious transfer, robust watermarking, and ZK proofs

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Reliability and Scalability

Blockchain Consensus

✦ Permissionless Setting ✦ Anybody interested can be a validator ✦ Proof of work-based consensus ✦ Slower (a few minutes)

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✦ Permissioned Setting ✦ The pre-defined-but-adaptive set of validators ✦ Asynchronous Atomic Broadcast ✦ Fast and cheap (mater of a few seconds)

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✦ Permissioned Setting ✦ The pre-defined-but-adaptive set of validators ✦ Asynchronous Atomic Broadcast ✦ Fast and cheap (mater of a few seconds)

18Sawtooth Lake

Scalability in the Permissionless Setting

✦ Payment Channels

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LIAR, LIAR, COINS ON FIRE!TIM RUFFING, @REAL_OR_RANDOM

Fast transactions(no double-spending)

Several transactions in a scalable manner

Channel establishment with predetermined party

Bitcoin Payment Channels

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5 4 3 2 1 0


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5 4 3 2 1 0


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5 4 3 2 1 0

Payment Channel Networks

✦ Extending Payment channel transactions across different parties to allow multi-hop scalable transactions

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Public Ledger and Privacy

Linkability of Bitcoin Pseudonyms

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A

B'

A'


AddressesOutput


σA

A’: 69.345


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A

B'

A'


AddressesOutput


σA

A’: 69.345


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A

B'

A'

A''

A'''

C'

D'

Deanonymization Attacks in Practice

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[Meiklejohn et al., IMC'13]Bitcoin Deanonymization


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[Meiklejohn et al., IMC'13]Bitcoin Deanonymization

Rippex

RippleLabsRippleLabs

ICE

Ripula

Bullion

DividendRippler

Bitstamp

SnapSwap

PanamaBitcoins

LakeBTC

rippleSingaporeWisePass

RippleCN

Coinex

DYM

WeExchange

Spam

RippleDividend

RippleFox

Hongfei

Bitso

chriswen

CoinPipDevcoin/Ripple

[Moreno-Sanchez et al., PETS'16]Ripple Deanonymization

Transactions Unlinkability

✦ Several Solutions (with different properties, assumptions, and compatibility)

✦ Zerocoin, Zerocash

✦ Coinjoin -Mixcoin, Coinshuffle, Coinshuffle++, Tumblebit, …

✦ Monero

✦ PathShuffle

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Privacy: Open Challenges

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In the Future

✦ The Interledger Protocol https://www.w3.org/community/interledger

✦ Several distributed/decentralized/centralized ledger solutions are coming up

✦ Performing transactions across different ledgers

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Our Internet of Value Research Team

✦ PhD Students and PostDoc

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Tim Ruffing Pedro Moreno-Sanchez Sze yiu Chau Srivatsan Ravi

Easwar Mangipudi

Our Internet of Value Research Team

✦ PhD Students and PostDoc

✦ Masters and Undergraduate Assistants

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Tim Ruffing Pedro Moreno-Sanchez Sze yiu Chau Srivatsan Ravi

Easwar Mangipudi

Krutarth R RaoSiddharth Gupta Mahimna Kelkar

Take home message

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✦ Self executing scripts/program program that directly controls the transfer of digital currencies or assets between parties under certain conditions

✦ Example Contracts: ✦ Assurance contracts/crowd funding ✦ payment channels for fast payments ✦ fair exchanges and lotteries ✦ Non-equivocation contracts [CCS ’15]

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Faster Cheaper

Privacy: Open Challenges

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Local Global

Centralized


2000-2010

Crypto-currencies may not survive,

but the concept of distributed

ledger/blockchain is here to stay

2

2010 onwards



8


Scalability

Privacy

Science

Smart Contracts

Applications

Blockchains: Science and Applications · Blockchain Technology: Applications Payment Systems Crypto-currencies such as Bitcoin and Ethereum Payment settlement IOweYou credit networks

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