1.
Blockchain in
perspective
Implications of blockchain design

2.
The principles of protocol

3.
Decentralization
Designing the ledger as a P2P network with complete replication of
knowledge removes a single point of failure, increases availability and
makes any data readable by any node.
The principles of blockchain

4.
Complete, immutable log of operations
The data in blockchain is represented as an append-only, ordered record
of transactions rather than a transitive state of users possession at any
point in time. The point of this design is increased auditability and
guaranteed atomicity of operations.
The principles of blockchain

5.
Total order of transactions
The operations in blockchain must be stored in the exactly same order
on each node. It is important to keep the state derived from log
consistent, while forcing the network to execute a consensus algorithm
for every transaction.
The principles of blockchain

6.
Providing trust in absence of middleman
Replicating a complete, globally ordered, immutable log of transaction
across the entire network allows each node to derive a current state of
processing, thus making it possible to issue, verify and commit only valid
transactions.
The principles of blockchain

7.
Breakthrough
technology!

8.
The future of
banking!

9.
Power to the
people!

10.
well...

11.
The cost of blockchain consensus
source

12.
The cost of blockchain consensus
source

13.
The cost of blockchain consensus
source

14.
There are more concerns:
● Security depends on network size (mostly)
● The format of register is very limited
● The guarantees offered by blockchain can be achieved easily by a
middleman
○ Event sourcing
○ Master-slave replication
○ Asymmetric cryptography
The issues

15.
Distributed, append only, HA log
● Apache Kafka
● Relational Databases
● ...
The issues

16.
Total order of transactions
● Comes down to solving consensus
● Paxos, …
● Can be handled by atomic commits
● 2PC, 3PC*
The issues

17.
Accountability
● Cryptographic keys
● Trust provided by a third party
The issues

18.
So, why do I even need it?

19.
What now?

20.
Do I really need to
store anything?
Do I need blockchain

21.
Do I need to model
the transfer of
value?
Do I need blockchain

22.
Do I need to
handle writes from
multiple sources?
Do I need blockchain

23.
Do the writing
parts trust each
other?
Do I need blockchain

24.
Is there a trusted
third-party? Can I
become one?
Do I need blockchain

25.
Can blockchain
meet my
requirements?
Do I need blockchain

26.
Don’t use
blockchain*

27.
Find a technology
that solves your
problem

28.
*It could be
blockchain after all

29.
Thank you!
Poznań / Helsinki / San Francisco

30.
References
● https://www2.deloitte.com/content/dam/Deloitte/ie/Documents/Technology/IE_C_block
chain_performance_report.pdf - Blockchain performance report
● https://arxiv.org/pdf/1308.1358.pdf - Paxos performance paper
● https://medium.com/@sbmeunier/when-do-you-need-blockchain-decision-models-
a5c40e7c9ba1 - Different models of deciding on using blockchain
Further reading