Secureum Book
  • 🛡️Secureum Bootcamp
    • 🛡️Secureum Bootcamp
    • 🙌Participate
    • 📜History
  • 📚LEARN
    • Introduction
      • 🔷1. Ethereum Basics
        • 1.1 Ethereum: Concept, Infrastructure & Purpose
        • 1.2 Properties of the Ethereum Infrastructure
        • 1.3 Ethereum vs. Bitcoin
        • 1.4 Ethereum Core Components
        • 1.5 Gas Metering: Solving the Halting Problem
        • 1.6 web2 vs. web3: The Paradigm Shift
        • 1.7 Decentralization
        • 1.8 Cryptography, Digital Signature & Keys
        • 1.9 Ethereum State & Account Types
        • 1.10 Transactions: Properties & Components
        • 1.11 Contract Creation
        • 1.12 Transactions, Messages & Blockchain
        • 1.13 EVM (Ethereum Virtual Machine) in Depth
        • 1.14 Transaction Reverts & Data
        • 1.15 Block Explorer
        • 1.16 Mainnet & Testnets
        • 1.17 ERCs & EIPs
        • 1.18 Legal Aspects in web3: Pseudonymity & DAOs
        • 1.19 Security in web3
        • 1.20 web2 Timescales vs. web3 Timescales
        • 1.21 Test-in-Prod. SSLDC vs. Audits
        • Summary: 101 Keypoints
      • 🌀2. Solidity
        • 2.1 Solidity: Influence, Features & Layout
        • 2.2 SPDX & Pragmas
        • 2.3 Imports
        • 2.4 Comments & NatSpec
        • 2.5 Smart Contracts
        • 2.6 State Variables: Definition, Visibility & Mutability
        • 2.7 Data Location
        • 2.8 Functions
        • 2.9 Events
        • 2.10 Solidity Typing
        • 2.11 Solidity Variables
        • 2.12 Address Type
        • 2.13 Conversions
        • 2.14 Keywords & Shorthand Operators
        • 2.15 Solidity Units
        • 2.16 Block & Transaction Properties
        • 2.17 ABI Encoding & Decoding
        • 2.18 Error Handling
        • 2.19 Mathematical & Cryptographic Functions
        • 2.20 Control Structures
        • 2.21 Style & Conventions
        • 2.22 Inheritance
        • 2.23 EVM Storage
        • 2.24 EVM Memory
        • 2.25 Inline Assembly
        • 2.26 Solidity Version Changes
        • 2.27 Security Checks
        • 2.28 OpenZeppelin Libraries
        • 2.29 DAppSys Libraries
        • 2.30 Important Protocols
        • Summary: 201 Keypoints
      • 🔏3. Security Pitfalls & Best Practices
        • 3.1 Solidity Versions
        • 3.2 Access Control
        • 3.3 Modifiers
        • 3.4 Constructor
        • 3.5 Delegatecall
        • 3.6 Reentrancy
        • 3.7 Private Data
        • 3.8 PRNG & Time
        • 3.9 Math & Logic
        • 3.10 Transaction Order Dependence
        • 3.11 ecrecover
        • 3.12 Unexpected Returns
        • 3.13 Ether Accounting
        • 3.14 Transaction Checks
        • 3.15 Delete Mappings
        • 3.16 State Modification
        • 3.17 Shadowing & Pre-declaration
        • 3.18 Gas & Costs
        • 3.19 Events
        • 3.20 Unary Expressions
        • 3.21 Addresses
        • 3.22 Assertions
        • 3.23 Keywords
        • 3.24 Visibility
        • 3.25 Inheritance
        • 3.26 Reference Parameters
        • 3.27 Arbitrary Jumps
        • 3.28 Hash Collisions & Byte Level Issues
        • 3.29 Unicode RTLO
        • 3.30 Variables
        • 3.31 Pointers
        • 3.32 Out-of-range Enum
        • 3.33 Dead Code & Redundant Statements
        • 3.34 Compiler Bugs
        • 3.35 Proxy Pitfalls
        • 3.36 Token Pitfalls
        • 3.37 Special Token Pitfalls
        • 3.38 Guarded Launch Pitfalls
        • 3.39 System Pitfalls
        • 3.40 Access Control Pitfalls
        • 3.41 Testing, Unused & Redundand Code
        • 3.42 Handling Ether
        • 3.43 Application Logic Pitfalls
        • 3.44 Saltzer & Schroeder's Design Principles
        • Summary: 201 Keypoints
      • 🗜️4. Audit Techniques & Tools
        • 4.1 Audit
        • 4.2 Analysis Techniques
        • 4.3 Specification, Documentation & Testing
        • 4.4 False Positives & Negatives
        • 4.5 Security Tools
        • 4.6 Audit Process
        • Summary: 101 Keypoints
      • ☝️5. Audit Findings
        • 5.1 Criticals
        • 5.2 Highs
        • 5.3 Mediums
        • 5.4 Lows
        • 5.5 Informationals
        • Summary: 201 Keypoints
  • 🌱CARE
    • CARE
      • CARE Reports
  • 🚩CTFs
    • A-MAZE-X CTFs
      • Secureum A-MAZE-X
      • Secureum A-MAZE-X Stanford
      • Secureum A-MAZE-X Maison de la Chimie Paris
Powered by GitBook
On this page
  1. LEARN
  2. Introduction
  3. 3. Security Pitfalls & Best Practices

3.7 Private Data

This security pitfall is related to the notion of what is private data on a blockchain or the privacy of on-chain data.

Remember that state variables and Solidity have a function visibility specifier. By making this specified a private, such private state variables can't be read only by other smart contracts on the blockchain, this does not mean that they can't be read at all.

We don't have to believe that they are considered private in a confidentiality perspective because the state of such variables and contracts and transactions in general on the blockchain can be read by anyone on the chain itself or via off-chain interfaces by querying the mempools for transactions or by querying the contract state itself to look at what values such private variables contain.

This effectively means that, there is no notion of data being private on the blockchain and any such data for confidentiality reasons that needs to be private should be encrypted and stored off-chain.

Previous3.6 ReentrancyNext3.8 PRNG & Time

Last updated 1 year ago

📚
🔏