1. Kickoff Presentation Master’s Thesis: Identification of Programming Patterns in Solidity
Franz Volland, 29th January 2018, Scientific advisor: Ulrich Gallersdörfer

2. Agenda 1 2 3 4 5 6 From Blockchain to Solidity – A Short Introduction
Motivation 3
Research Questions 4
Approach & Methods 5
Possible Pattern Categories 6
Thesis Plan
Identification of Programming Patterns in Solidity
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3. From Blockchain to Solidity - A Short Introduction
TIME:
PREV. HASH:
98A3B821A7
<TRANSACTIONS>
BLOCK 12347
BLOCK 12348
A  B : 2Ƀ
A  C : 0.2Ƀ
B –> C : 1Ƀ
A  B : 2Ξ
A  Code
B  Code.do()
Solidity:
Smart contract programming language
Similar to JavaScript
Announced 2014
Identification of Programming Patterns in Solidity
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4. Motivation – Why we need Patterns for Solidity
Major Hacks:
The DAO: 3.6M Ξ (~3.6 billion $)
Parity Multisignature Wallet 2x 150k + 514k Ξ (~0.66 billion $)
“We are in Cryptoland. […] It‘s like Australia
where anything with a heartbeat will try to kill you.“
- Martin Swende (Ethereum Foundation)
Current Problems:
Solidity Patterns useful for:
A lot of attackers
High stakes
Language is new for everyone
Non trivial to understand
Easy to mess up
No chance to easily fix mistakes
Developers AND Users
Identification of Programming Patterns in Solidity
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5. Motivation – Example Exploit: Reentrancy
Total Balance: Ξ
userBalances[User]: 100Ξ
withdrawBalance
withdrawBalance
100Ξ
100Ξ
withdrawBalance
User
Contract
Evil Contract
Contract
100Ξ
+100Ξ
Total Balance: 900Ξ
userBalances[User]: 0Ξ
Total Balance: 0Ξ
userBalances[User]: 100Ξ
+1000Ξ …
Identification of Programming Patterns in Solidity
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6. What is the current state of software engineering in Solidity?
Research Questions
What is the current state of software engineering in Solidity?
What is the process of designing and implementing smart contracts on the Ethereum blockchain?
What are current challenges in smart contract development using Solidity?
Are there any best practices or patterns in smart contract development and how can they be categorized?
Identification of Programming Patterns in Solidity
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7. Approach & Methods Modified Gang of Four1 Taxonomy: Research on:
Intent
Also Known As
Motivation
Applicability
Structure
Participants
Collaboration
Consequences
Implementation
Sample Code
Known Uses
Related Patterns
Research on:
Papers
DApp Portals
ICO Portals
GitHub
Blogs
Code
1 Gamma et al.: Design Patterns: Elements of Reusable Object-Oriented Software
Identification of Programming Patterns in Solidity
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8. Possible Pattern Categories
Security
Maintainability
Access Restriction
Pull over Push
Checks-Effects-Interaction
Secure Transfer
Upgrading Contracts
Functionality into Libraries
Utility
Voting
Randomness
Crowdfunding
Oracle
Function Scheduling
Auction
Bounty
Administration
Economic
State Machine
String Compare
Pause
Assertion
Suiciding
Packing Structs
Memory Array Building
Identification of Programming Patterns in Solidity
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9. Thesis Plan December January February March April May June
Literature / Research
Concept Creation
Information Assembly
Evaluation
Writing
Registration Date
Kickoff Presentation
Identification of Programming Patterns in Solidity
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10. Franz Volland
17135

11. Patterns included in Solidity Documentation
Identification of Programming Patterns in Solidity
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12. Additional Attacks and Blunders
Identification of Programming Patterns in Solidity
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13. Programming Language Comparison
Feature
Java
Solidity
Haskell
Programming Paradigm
Object-oriented
Contract-oriented
Functional
Concurrency?
Multi-threading
Serial execution
Polymorphism?
Through overloading
Through interfaces
Parametric & Ad-hoc
Static/Dynamic Typing?
Statically-typed
Strong/Weak Typing?
Strong
Higher-order Functions?
With Lambda expressions (Java8)
Not supported
Supported
Inheritance?
Interfaces?
Type classes, similar
Type inference?
Loops?
Switches?
Via Case-expression
If-Else?
Identification of Programming Patterns in Solidity
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