1. Blockchain:
Overview, Use Cases and
Challenges
Sebastien Tandel sta@hpe.com
March 2017

2. Agenda
– Blockchain a Trend?
– Blockchain Explained
– Overview
– Use Cases & Implementations
– Challenges
–Take Aways

3. Blockchain a Trend?
3

4. as a Trend

5. Blockchain by numbers
2015: 42 systemic financial institutions in a consortium
2016: $1.4+ billion invested in Blockchain
By 2022: Blockchain business worth $10B✽
✽ Gartner Top Predictions 2017

6. Blockchain Explained
6

7. Blockchain 101
Alice agreed on a
transaction with Bob
The transaction is signed
and a block is created to
represent that transaction
The block is broadcast
and validated by the
blockchain network
The block is added to the chain,
providing a permanent
non-repudiable and transparent
record of the transaction

8. Blockchain 101 : What the hell is a Blockchain?
–Blockchain is a database that is
–De-centralized
–Append-only (entries are immutable)
–Recording transactions between 2+ parties (Alice & Bob)
–Which parties trust because of a distributed consensus protocol
–Achieved by a network of (untrusted) participants
–And ultimately secured through some cryptographic work

9. Blockchain 101: OK, got it… but why?
centralized
ledger
de-centralized
ledger
Santander : by 2022, could cut banks infrastructure costs by $15-20bn a year
for cross-border payments, securities trading and regulatory compliance

10. What is a block?
BLOCK
Blocks are units of the Blockchain
HEADER
Version
Merkle Root
Difficulty
Previous Block
Hash
Timestamp
Nonce
TRANSACTION COUNT
BLOCK CONTENT
Coinbase TX Bitcoin TX
Total Bitcoin + Coinbase TX

11. How a block is added to blockchain?
Proof Of Work : “mining” in bitcoin world
• Participants create one block from the current transactions
• and tries to solve a complex challenge:
• hash of block header with X leading 0s, varying “nonce”
Ø hard to compute, very easy to verify
• Each 10 minutes (avg time for 1 node to find a valid hash),
the block is added to the chain
Ø Challenge Complexity is periodically adjusted to maintain the
10 minutes constant
BLOCK
Blocks are units of the Blockchain
HEADER
Version
Merkle Root
Difficulty
Previous Block
Hash
Timestamp
Nonce
TRANSACTION COUNT
BLOCK CONTENT
Coinbase TX Bitcoin TX
Total Bitcoin + Coinbase TX

12. Why is there any participant at all?
–Indeed LOT of resources wasted to solve the challenge of 1 block
–Keep in mind everyone competes on the same block, to get only 1 winner !
–Why would anyone participate? Economics! Well... money J
–In Bitcoin world, the winning miner is awarded some coinbase
–in 2015, it was 25BTC and worth US$6900 ; 2017, 12.5 BTC
–Owner of a transaction may also give a tip to the winner.

13. Why is this secure?
1. Transactions are cryptographically signed
• To ensure/verify ownership of a transaction!Owner 1’s
Public Key
Transaction
Owner 0’s
Signature
Owner 1’s
Private Key
Hash
Transaction
Owner 1’s
Signature
Owner 2’s
Public Key
Owner 2’s
Private Key
Hash
Transaction
Owner 2’s
Signature
Owner 3’s
Public Key
Owner 3’s
Private Key
Hash

14. Why is this secure?
1. Transactions are cryptographically signed
• To ensure/verify ownership of a transaction!Owner 1’s
Public Key
Transaction
Owner 0’s
Signature
Owner 1’s
Private Key
Hash
Transaction
Owner 1’s
Signature
Owner 2’s
Public Key
Owner 2’s
Private Key
Hash
Transaction
Owner 2’s
Signature
Owner 3’s
Public Key
Owner 3’s
Private Key
Hash
Better not lose that key or being stolen. This
is what defines ownership of a transaction.

15. Why is this secure?
1. Transactions are cryptographically signed
2. Transactions encoded into a Merkle Tree
• IOW, If you modify one bit of a transaction,
“root hash” would change
BLOCK
Hash1
HEADER
Version
Merkle Root
Previous Block
Hash
Timestamp
Nonce
TX1
Hash2
Difficulty
Hash3 Hash4
TX2
Hash12
TX3 TX4
Hash34

16. Why is this secure?
1. Transactions are cryptographically signed
2. Transactions encoded into a Merkle Tree
3. Mining challenge based hashing block header
• which includes the merkle tree root hash
BLOCK
HEADER
Version
Merkle Root
Difficulty
Previous Block
Hash
Timestamp
Nonce
TRANSACTION COUNT
BLOCK CONTENT
Coinbase TX Bitcoin TX
Total Bitcoin + Coinbase TX

17. Why is this secure?
1. Transactions are cryptographically signed
2. Transactions encoded into a Merkle Tree
3. Mining challenge based hashing block header
• which includes the merkle tree root hash
• AND previous block header hash
• hash chaining: with age, block becomes
more secure
BLOCK
HEADER
Version
Merkle Root
Difficulty
Previous Block
Hash
Timestamp
Nonce
TRANSACTION COUNT
BLOCK CONTENT
Coinbase TX Bitcoin TX
Total Bitcoin + Coinbase TX
more
secure

18. Why is this secure?
1. Transactions are cryptographically signed
2. Transactions encoded into a Merkle Tree
3. Mining challenge based hashing block header
4. Easy to validate and check integrity based on
computed hashes and signatures
• When a block is broadcast, all nodes verify
its validity and integrity. If not valid, reject.
BLOCK
HEADER
Version
Merkle Root
Difficulty
Previous Block
Hash
Timestamp
Nonce
TRANSACTION COUNT
BLOCK CONTENT
Coinbase TX Bitcoin TX
Total Bitcoin + Coinbase TX
more
secure

19. Blockchain Implementations & Use Cases

20. Blockchain Ecosystem for Financial Services

21. Blockchain Ecosystem for Non-Financial Services

23. Blockchain Implementations

24. Bitcoin 101 : Ecosystem
A bitcoin client is used to
generate addresses (keys)
& performing transactions (purchases)
Pool of bitcoin miners
Businesses can accept bitcoin
to sell to their customers
through bitcoin addresses (keys)
Market exchanges
to sell/buy bitcoins
for usual currencies
global peer-to-peer decentralized network

25. Bitcoin 101 : Transaction
Each transaction is a (list of) Bitcoin payment(s)
BLOCK
Blocks are units of the Blockchain
HEADER
Version
Merkle Root
Difficulty
Previous Block
Hash
Timestamp
Nonce
TRANSACTION COUNT
BLOCK CONTENT
Coinbase TX Bitcoin TX
Total Bitcoin + Coinbase TX
Transaction
TECHNICAL DATA
Version
#inputs
Lock Time (delay)
#outputs
INPUTS
OUTPUT
Script Len Lock Script
Previous TX Hash / Output Index
Unlock ScriptScript Len
Amount

26. Bitcoin 101: UTXO (Unspent Transaction Output)
Transaction TX0
Input0
Output0
Output1
100k
satoshis
40k
satoshis
50k
satoshis
Transaction TX1
Input0
Output0
Transaction TX2
Input0
Output0
Output1
20k
UTXO
Transaction TX3
Input0
Output0
Transaction TX4
Input0
Output0
20k
satoshis
20k
satoshis
10k
UTXO

27. Bitcoin Blockchain Challenges
– Transaction Rate
– Bitcoin block limited to 1MB, limiting #tx/block & 1 block added each 10min, limiting #tx/sec
– Oh right, and what about forks?
– All miners compete to solve the same Proof of Work. Forks happen when 2 miners solve it at the same time.
– Largest chain is considered the one to be used by miners
– Usually, it’s considered forks are solved by consensus within 6 blocks after the fork. (theoretical)
Bitcoin 7 tx/sec
VISA avg
VISA peak
2000 tx/sec
56K tx/sec
confirmed
tx
settled
tx
verified
tx
on avg
10 min
60 min
43 min
Note: Some transactions remain permanently
unverified (dependency on fee paid)

28. Bitcoin Blockchain Challenges
– The previous consensus of selecting the longest chain is subject to 51% attack
– If anyone controls more than 51% of total capacity Proof of Work power, she could alter the integrity of the blockchain
ØLarge number of participants is critical for these blockchains based on Proof of Work
– Currently for Bitcoin, it is admitted that not even governments could afford to build infrastructure able to represent
51% of the compute power of miners
– HOWEVER, mining competition is harsh:
–5 largest mining orgs >75% of total mining capacity (~1517 petahash/sec)
– Main hashing power in China! ; What-if collusion?

29. Bitcoin Blockchain Challenges
– Decreasing Profits for miners
– ~= 545 million revenue a year for miners
– Miner profits fall as the blockchain network expands.
– New block reward cut in half every 210,000 blocks (~4 years)
– Since transaction fees are presently around 50 times smaller than the block reward, reducing the block reward by half
cuts total mining revenues if the bitcoin transaction fees and price remain unchanged
– Some companies already filed bankruptcy last year because of that.
Ø careful to the 51% attack …

30. Ethereum : Generalizing Bitcoin Blockchain
– Step back to Bitcoin
– Transactions authenticated through Lock/Unlock Scripts.
– These are scripts running on top of a stack-based interpreter !
– Scripting language is pretty powerful BUT
1. not Turing-complete,
2. although could be used for other purpose, mainly there to validate monetary transactions
– Ethereum generalizes Bitcoin initial concept of these scripts with a proposal of
– providing a Turing-complete scripting language
– enabling other use cases than crypto-currency!
– Smart Contracts are born !

31. Ethereum : Smart Contracts
• Transaction: An Ether payment transaction can be sent
from one address to another address like in Bitcoin
• Achieves 1 tx each 14sec !
• Contract: Insert code into transaction Data field, and
send to null address – mined as a Contract
• Contract is addressable (like call to execute a
function)
• Compute: On-chain calculations can be performed and
data stored but costs Ether (measured in Gas)
• Accounts: No UTXO, state stores a list of accounts
(addresses), where each account has a balance
• Balance: Transaction is valid if sender account has
balance, then sending account debited and receiving
credited
Ethereum Transaction
TECHNICAL DATA
To (Null for Contract)
Gas Price
Ether to Transfer
Start Gas
DATA
Smart Contract Code for Execution on Chain
General Text
Nonce Signature

32. Blockchain Implementations Comparison
Blockchain Purpose Peer-to-peer
(decentralized)
Public/private
mining
Cryptographic
trust
Permissionless Centralized
control
Bitcoin Decentralized
Money
Yes Public Yes Yes No
Ethereum Decentralized
Apps
Yes Public Yes Yes No
Ripple Decentralized
Payments
Yes Private Yes No Yes
Hyperledger Decentralized
Apps
Yes Private Yes No Yes

33. Blockchain Use Cases

34. Blockchain for a Liquid Democracy
–Vote through your own (or a public) smartphone, laptop, desktop, …
– Accounts and Votes are put on the blockchain
– Votes are public and can be consulted by anybody
ØAnybody can verify vote count of candidates
Øprivacy preserved ‘cause no public association between public key à WHO voted (but for you).
– Estimated cost reduction for 100M voters:
– Blockchain voting costs: $50M (EC2 calculator)
– Ballot based election: $2 per person => $200M
Ø$150M vs $600M for US
Ø$100M vs $400M for Brazil
34

35. Blockchain for Supply Chain
–Provide ability to track/trace any operation done in a supply chain
–Giving ability to trace product from inception : what, who, where, when, …?
ØDetect (decrease) frauds,
ØDetect stolen merchandise,
ØEnsure no counterfeit,
ØEnsure no slavery used, …
– Everledger : track supply chain of diamonds ... 800.000 tracked to date.
– BlockVerify : verify medicine authenticity by scanning QR code on a box
– Kuovola Innovation: platform for smart “tendering”. Pallet with RFID tags to move from A to B... Companies
bidding and one selected with blockchain as intermediate.
35

36. Blockchain for Sharing Economy
–Creation of decentralized and “dematerialized” organizations
–Sharing Economy on Blockchain governed by and for the people
–Uber: why would Uber takes the largest share of profits generated?
–Solution -> decentralized carpooling platforms (Lazooz, ArcadeCity)
–Warning (food for thoughts):
–30 years ago: Internet was announced to get rid of all intermediates
–Today: Never in Human history, such level of centralization has been reached with a few big
giants controlling large chunks of the Internet (and real) economy at “planet-scale”
–Google, Apple, Facebook, Amazon, Uber, ...
36

37. Blockchain for Digital Identity
–Secure and efficient tracking and management of Digital Identities (& docs)
–Digital Identities, passports, e-residency, birth certificates, wedding certificates, online
account logins, …
ØResults in seamless sign-ons and reduced frauds
–One step further for brazilian:
ØImagine a world without “cartorios” ... What a dream! J
37

38. Blockchain for IoT
Yesterday:
closed and centralized
Today:
open and in the cloud
Tomorrow:
open and decentralized

39. Blockchain for IoT
– Decentralization of IoT networks : current client/server architecture won’t scale in future
– Filament
– Autonomous mesh networks for data collection and asset monitoring
– Blockchain to identify and authenticate devices
– Chain of Things: Explore blockchain for scale and security issues in IoT
– Hackathon related to solar energy in which they provide reliable and verifiable renewable data, speeding up incentive
settlements and reducing opportunities for fraud
– Company?
– Connected cars exchanging traffic information between themselves

40. Decentralized Autonomous Organization
miners validate
smart permit regulates
release & reporting
smart permit automatically notifies
government and records all activities
on blockchain
Firm is granted
a permit
IoT sensors monitor
and record releases
and variances
smart permit is
distributed via
blockchain automatic warning
or enforcement action

41. Blockchain Still Some Challenges Ahead

42. Blockchain Challenges cont’d
– Security
– Incidents:
– Bitcoin:
– 2013, man threw away his hard drive with his private key to unlock his wallet worth $7.5M
– 2014: Mt Gox got robbed of $350M
– 2016 study claims that between 2009 & 2015, 33% of Bitcoin exchanges have been hacked!
– DAO: June 2016, organization drained of $60M of Ether.
– DDoS on exchanges and mining pools
– 51% attack still a real concern
– Data integrity:
– malleability attack where an attacker intercepts, modifies and rebroadcasts a transaction, causing the transaction issuer to believe
that the original transaction was not confirmed.
– Some have been able to attack Bitcoin wallets in practice, requiring some modification in their implementation.
– Authentication & Cryptography issues:
– Private keys stored by Mt Gox stolen … sic.
– Proposal to use 2-factor authentication to increase authentication levels.
– Issue : successful attacks on 2-factor authentication have already appeared a while ago.

43. Blockchain Challenges cont’d
– Proof of Work = Tremendous Waste of Energy
– Estimated to $15M a day => 5.5B a year !
– Proof of Stake has been proposed (and implemented)
– which does not require to waste that much energy but smartly use bitcoins owned by miners
– Also accelerate the time to add a block to the block chain
– Proof of Stake still not used by Bitcoin and Ethereum though.

44. Blockchain Challenges cont’d
– Bitcoin Blockchain Size:
– 01/2015 : 30GB
– 01/2016 : 50 GB
– 01/2017 : 100GB
– And all miners must download the whole blockchain…
– potential solutions: hierarchy of chains or regional blockchains
– Be careful of the 51% attack though.
– Ethereum blockchain size is 17GB (as of May 2016)
– Smaller than Bitcoin although it’s only after 9 months of existence and way less users than Bitcoin network!
– proposed a lighweight node model (for lightweight devices such as smartphones) to be able to add blocks to the
blockchain without downloading the blockchain.

45. Blockchain Challenges cont’d
45

46. Blockchain Challenges cont’d : “Peak of Inflated Expectations”
46

47. Take Aways
– Blockchain creates trust between untrusted parties willing to agree on some kind of transactions
– No intermediate required (note: does not mean they won’t exist anymore!)
– Every transaction is authenticated
– State changes are transparent
– No single point of failure
– Blockchain generalization with Smart Contracts creates a global trust shared execution environment
– Potential to disrupt many businesses, from retail to govts, from finances to health care ($10B+ by 2022)
– Already huge investments from largest financial institutions to disrupt financial use cases. ($1.5B+ in 2016)
– Exciting technology to investigate although:
– Still exist some pretty tricky challenges to overcome, both technological and legal
– Still placed at Peak of Inflated Expectations in the Gartner hype cycle 2016

48. References

49. References
– Blockchain 101:
– When do you Need Blockchain?
– Magic of Mining, The Economist
– Bitcoin, Blockchain and the design elements explained
– http://www.gartner.com/newsroom/id/3482117
– Banks seek the key to Blockchain, Financial Times
– Blockchain Implementations:
– A Beginner’s guide to Ethereum
– Gentle Introduction to Smart Contracts
– Ethereum whitepaper
– Dragonchain: Disney’s blockchain
– Hyperledger
– Bitcoin stack machine scripts interpreter

50. References
– Blockchain Use Cases:
– Securing IoT with Blockchain
– For Insurers, #blockchain is the New Black
– Blockchain Voting System
– Blockchain to Revolutionize Supply Chain
– Smart Contracts: Innovation across Manufacturing Value Chains
– What Blockchain means for Sharing Economy?
– Blockchain Challenges:
– 51% attack
– Declining Profitability for New Bitcoin Miners
– Alternatives for Proof of Work, Part 1
– Top 10 mistakes in Enterprise Blockchain Projects
– Bitcoin blockchain transaction delays
– Where is Current Research on Blockchain Technology – A Systematic Review