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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]
2
Ever Changing Landscape of Communication
Local Global2000-2010
3
Ever Changing Landscape of Communication
Local Global2000-2010
3
Ever Changing Landscape of Communication
Local Global
Centralized
2000-2010
3
Ever Changing Landscape of Communication
Local Global
Centralized
2000-2010
3
2010 onwards
Ever Changing Landscape of Communication
Local Global
Centralized
Decentralized/ Distributed
2000-2010
3
2010 onwards
Ever Changing Landscape of Communication
Local Global
Centralized
Decentralized/ Distributed
2000-2010
3
2010 onwards
Ever Changing Landscape of Communication
Local Global
Centralized
Decentralized/ Distributed
2000-2010
3
2010 onwards
Blockchain for Everything!
Ever Changing Landscape of Communication
Local Global
Centralized
Decentralized/ Distributed
2000-2010
Crypto-currencies may not survive,
but the concept of distributed
ledger/blockchain is here to stay
3
2010 onwards
Blockchain for Everything!
Blockchain can change ... well everything
4
Source: CB Insights
Blockchains can change a lot of things
5Source: 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.
6
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.
6
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!
7
Money to the island of Yap
Bitcoin/Blockchain Basics
8
Bitcoin TransactionInput
AddressesOutput
AddressesA: B70.345 B': B1
σA
A’: 69.345
sk: signing keyvk: verification key
A: Bitcoin AddressA = Hash(vk)
sk
Bitcoin/Blockchain Basics
8
Bitcoin TransactionInput
AddressesOutput
AddressesA: B70.345 B': B1
σA
A’: 69.345
sk: signing keyvk: verification key
A: Bitcoin AddressA = Hash(vk)
sk
Bitcoin/Blockchain Basics
8
Bitcoin TransactionInput
AddressesOutput
AddressesA: B70.345 B': B1
σA
A’: 69.345
sk: signing keyvk: verification key
A: Bitcoin AddressA = Hash(vk)
public list of transactions or Blockchain
sk
Our Research Thrusts
9
Blockchain Technology
Our Research Thrusts
9
Blockchain Technology
Scalability
Privacy
Science
Our Research Thrusts
9
Blockchain Technology
Scalability
Privacy
Science
Smart Contracts
Applications
Core Bitcoin Technology: Blockchains
10
Core Bitcoin Technology: Blockchains
✦ Blockchain -An asset database that aggregates transactions in blocks, and
these blocks are appended to a chain of existing blocks
10
Core Bitcoin Technology: Blockchains
✦ Blockchain -An asset database that aggregates transactions in blocks, and
these blocks are appended to a chain of existing blocks
✦ Replications - The blockchain is shared across a global network, such that all
participants can have their own identical copy of the ledger
10
Core Bitcoin Technology: Blockchains
✦ Blockchain -An asset database that aggregates transactions in blocks, and
these blocks are appended to a chain of existing blocks
✦ Replications - The blockchain is shared across a global network, such that all
participants can have their own identical copy of the ledger
✦ Use digital signatures - to control who can do what within the shared ledger
10
Core Bitcoin Technology: Blockchains
✦ Blockchain -An asset database that aggregates transactions in blocks, and
these blocks are appended to a chain of existing blocks
✦ Replications - The blockchain is shared across a global network, such that all
participants can have their own identical copy of the ledger
✦ 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
10
Blockchain Technology: Applications
11
Blockchain Technology: Applications
✦ Payment Systems ✦ Crypto-currencies such as Bitcoin and
Ethereum ✦ Payment settlement IOweYou credit
networks such as Ripple and Stellar ✦ Developing the Internet of Value
11
Blockchain Technology: Applications
✦ Payment Systems ✦ Crypto-currencies such as Bitcoin and
Ethereum ✦ Payment settlement IOweYou credit
networks such as Ripple and Stellar ✦ Developing the Internet of Value
✦ Identity Management
11
Blockchain Technology: Applications
✦ Payment Systems ✦ Crypto-currencies such as Bitcoin and
Ethereum ✦ Payment settlement IOweYou credit
networks such as Ripple and Stellar ✦ Developing the Internet of Value
✦ Identity Management
✦ Supply Chain Management ✦ Track Diamonds, food, Goods
11
Applications: Smart Contracts
Bitcoin Smart Contracts
✦ Self executing scripts/programs that directly control the transfer of currencies/assets between parties under certain conditions
13
Self-Imposable Trustless
Faster Cheaper
Bitcoin Smart Contracts
✦ 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]
13
Self-Imposable Trustless
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…
14
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…
✦ Extremely common across industry, and often breached! ✦ Latest Example:
Scorpene submarine data leak from French manufacturer DCNS
14
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…
✦ 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
14
Non-Disclosure Agreement (NDA): Today
15
Non-Disclosure Agreement (NDA): Today
15
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
16
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
✦ 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
16
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
✦ 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
16
Reliability and Scalability
Blockchain Consensus
✦ Permissionless Setting ✦ Anybody interested can be a validator ✦ Proof of work-based consensus ✦ Slower (a few minutes)
18
Blockchain Consensus
✦ Permissionless Setting ✦ Anybody interested can be a validator ✦ Proof of work-based consensus ✦ Slower (a few minutes)
✦ Permissioned Setting ✦ The pre-defined-but-adaptive set of validators ✦ Asynchronous Atomic Broadcast ✦ Fast and cheap (mater of a few seconds)
18
Blockchain Consensus
✦ Permissionless Setting ✦ Anybody interested can be a validator ✦ Proof of work-based consensus ✦ Slower (a few minutes)
✦ 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
19
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
20
5 4 3 2 1 0
Bitcoin Payment Channels
20
5 4 3 2 1 0
Bitcoin Payment Channels
20
5 4 3 2 1 0
Payment Channel Networks
✦ Extending Payment channel transactions across different parties to allow multi-hop scalable transactions
21
Public Ledger and Privacy
Linkability of Bitcoin Pseudonyms
23
A
B'
A'
Bitcoin TransactionInput
AddressesOutput
AddressesA: B70.345 B': B1
σA
A’: 69.345
Linkability of Bitcoin Pseudonyms
23
A
B'
A'
Bitcoin TransactionInput
AddressesOutput
AddressesA: B70.345 B': B1
σA
A’: 69.345
Linkability of Bitcoin Pseudonyms
24
A
B'
A'
A''
A'''
C'
D'
Deanonymization Attacks in Practice
25
Deanonymization Attacks in Practice
25
[Meiklejohn et al., IMC'13]Bitcoin Deanonymization
Deanonymization Attacks in Practice
25
[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
26
Privacy: Open Challenges
27
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
28
Our Internet of Value Research Team
✦ PhD Students and PostDoc
29
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
29
Tim Ruffing Pedro Moreno-Sanchez Sze yiu Chau Srivatsan Ravi
Easwar Mangipudi
Krutarth R RaoSiddharth Gupta Mahimna Kelkar
Take home message
30
Bitcoin Smart Contracts
✦ 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]
11
Self-Imposable Trustless
Faster Cheaper
Privacy: Open Challenges
23
Ever Changing Landscape of Communication
Local Global
Centralized
Decentralized/ Distributed
2000-2010
Crypto-currencies may not survive,
but the concept of distributed
ledger/blockchain is here to stay
2
2010 onwards
Blockchain for Everything!
Our Research Thrusts
8
Blockchain Technology
Scalability
Privacy
Science
Smart Contracts
Applications