What is a blockchain? How do the existing contenders compare? Listing purpose and features of Bitcoin, Zerocash, Ripple, Stellar, Hyperledger, Ethereum, Tendermint and Eris on that basis. Talk at the 3rd Blockchain Workshop, London 2015. By one of the pre-eminent blockchain researchers, Vlad Zamfir.

1. Demystifying Blockchains
Henning Diedrich & Vlad Zamfir
Blockchain Workshops • London 2015

2. Bitcoin and the blockchain
● power
● hype
● reality

3. Bitcoin’s innovations
● blockchains
● economic consensus

4. Projects
● Bitcoin
● Ripple
● Stellar
● Hyperledger
● Ethereum
● Eris
● Tendermint

5. What is Consensus?
● Consensus protocols are used to make ONE
reliable computer out of many unreliable or
untrusted computers

6. What is Consensus?
● They are used in real-life applications
○ processors
○ databases
○ flying cars

7. Traditional Consensus Protocols
● Clients in these protocols only change their
state when a supermajority approves of the
changes, or elects a leader who proposes
the changes
tc

8. Traditional Consensus Protocols
tc
● Coordinate on changes to the state
● Changes are never reverted
● They “just stop” if too many nodes go offline

9. ● Blockchains are consensus protocols that
come to consensus through compromise
● “Fork-choice rule”
What is a blockchain?
BC

10. Why a blockchain?
● They are available in the event of network
partitions
● Blockchains are more decentralized than
traditional consensus protocols
BC

11. “Maintain a shared, trusted computer even though we don’t
trust each other because we know that screwing it up would
cost us a lot of money.” - The Joker
What is Economic Consensus?
eeconomic

12. ● Public consensus
● Guarantees correctness
○ even for private consensus
○ “trustless”
“Maintain a shared, trusted computer even though we don’t
trust each other because we know that screwing it up would
cost us a lot of money.” - The Joker
Why Economic Consensus?
eeconomic

13. How do we make faults expensive?
● Proof-of-work
○ Make changing the state expensive
● Proof-of-stake
○ Use security deposits to punish nodes who propose
competing updates to the consensus
eeconomic

14. Blockchain projects
● Bitcoin
● Ripple
● Stellar
● Hyperledger
● Ethereum
● Eris
● Tendermint

15. Bitcoin disintermediate banks
& currencies

16. Zerocash
anonymous
Bitcoin

17. Ripple
replace SWIFT

18. Stellar
bank the unbanked

19. Hyperledger
inter-bank clearing

20. Ethereum
public
smart contract
platform

21. public
smart contract
platform
Tendermint

22. Eris
private
smart contracts
platform stack

23. Core Design
❏ private
❏ public
❏ traditional consensus protocol
❏ decentralized blockchain
❏ transaction network
❏ virtual machine

24. Bitcoin disintermediate banks & currencies
public, decentralized blockchain
+ virtual machine

25. replace SWIFT
Ripple
private transaction network
with built-in currency conversions

26. bank the unbanked
Stellar
private transaction network
with built-in currency conversions

27. Hyperledger
inter-bank clearing
private consensus protocol

28. Ethereum
public
smart contract
platform
public, decentralized blockchain
+ virtual machine

29. Tendermint
public, decentralized blockchain
+ virtual machine
public
smart contract
platform

30. Eris
private
smart contracts
platform stack
private consensus
+ virtual machine

31. Smart Contracts
● Virtual machine ...
● … with transaction capacity (token)
● Oracle input from outside world

32. Smart Contracts
Bitcoin Ethereum Tendermint Eris

33. Smart Contracts
Bitcoin VM Ethereum Virtual Machine
(EVM)
Bitcoin Ethereum Tendermint Eris

34. “Maintain a shared,
trusted computer
even though we
don’t trust each
other because we know that screwing
it up would cost us a lot of money.”
What is Economic Consensus?
eeconomic

35. Bitcoin disintermediate banks & currencies
public, decentralized blockchain
+ virtual machine
eeconomic
BC

36. non-economic
e
Ripple
replace SWIFT
private transaction network
with built-in currency conversions

37. bank the unbanked
e
Stellar
private transaction network
with built-in currency conversions
non-economic
enon-economic

38. inter-bank clearing
private consensus protocol
tc
e
Hyperledger
non-economic

39. public
smart contract
platform
Ethereum
public, decentralized blockchain
+ virtual machine
eeconomic
BC

40. Tendermint
public
smart contract
platform
public, decentralized blockchain
+ virtual machine
tc
eeconomic

41. Eris
private
smart contracts
platform stack
private consensus
+ virtual machine
enon-economic
tc
enon-economic

42. Thank You!
Questions!

43. Credits
Roof top - © Can Stock Photo Inc. / solarseven
Handshake - © Can Stock Photo Inc. / a_papantoniou
Roman - © Can Stock Photo Inc. / Nejron
Chain ball - © Can Stock Photo Inc. / 3quarks
Joker - © Can Stock Photo Inc. / sad
Ring - © Can Stock Photo Inc. / Marisabell
Iron claw - © Can Stock Photo Inc. / andreykuzmin
Swordman - © Can Stock Photo Inc. / prometeus
Monk – © Can Stock Photo Inc. / FotoMaximum
Colour man - © Can Stock Photo Inc. / alphaspirit
Hero girl - © Can Stock Photo Inc. / Choreograph
White boy - © Can Stock Photo Inc. / prometeus
Sword giver - © Can Stock Photo Inc. / prometeus
Blue android - © Can Stock Photo Inc. / leafsomen
Blue girl - © Can Stock Photo Inc. / FotoMaximum
Green robot - © Can Stock Photo Inc. / leafsomen