8. Beyond the Digital: Risks and Challenges in Blockchain Networks

8.1 Oracle Problem

Blockchain networks work extremely well with the data within their own digital systems. However, when they need to interact with the real world, there are issues often referred to as the Oracle Problem. A blockchain network can record both human input data as well as sensor input data from the real world, but there may be no method to determine if the input data reflects actual real-world events.

Sensor errors: Sensors may malfunction and record inaccurate data.
Human error or deception: Humans could record false information, intentionally or unintentionally.

These issues are not unique to blockchain networks but affect digital systems overall. For pseudonymous blockchain networks, dealing with data misrepresentation outside of the digital network can be particularly problematic.

For example, if a cryptocurrency transaction occurs to purchase a real-world item, the blockchain cannot verify whether the shipment actually took place without relying on external sensor or human input.

Several projects have attempted to address the Oracle problem and create reliable mechanisms to ingest external data in a trustworthy and accurate way. Examples include:

Oraclize: Converts web API data into blockchain-readable bytecode, though it may introduce a single point of failure.
Mineable Oracle Contract: Uses blockchain-inspired consensus and economic incentives to ingest data securely.

8.2 Blockchain Death

Traditional centralized systems are created and shut down constantly, and blockchain networks are likely no different. However, due to decentralization, a blockchain network may never be fully shut down, with some nodes potentially remaining operational indefinitely.

A defunct blockchain would not serve as a reliable historical record, as a small number of publishing nodes could be overpowered by malicious users who could redo and replace any number of blocks.

8.3 Cybersecurity

Blockchain technology does not eliminate inherent cybersecurity risks. Human factors remain a significant threat, making a robust cybersecurity program essential to protect the network and participating organizations.

Existing cybersecurity standards and guidance remain relevant for blockchain systems. Adjustments may be needed to account for blockchain-specific attributes, but frameworks such as the NIST Cybersecurity Framework provide a strong foundation to identify and control risks affecting blockchain networks.

8.3.1 Cyber and Network-based Attacks

Despite being tamper evident and tamper resistant, blockchain networks are still vulnerable:

Transactions not yet included in published blocks can be manipulated.
Attacks on timestamps or ordering services can affect transaction validity.
Denial-of-service (DoS) attacks may target the blockchain platform or smart contracts.
Malicious actors can conduct network scanning, reconnaissance, or zero-day attacks.
Newly deployed smart contracts may contain vulnerabilities that can be exploited similarly to traditional web applications.

8.4 Malicious Users

While blockchain networks enforce transaction rules, they cannot enforce user behavior. This is particularly challenging for permissionless networks, where users are pseudonymous.

Even though rewards (e.g., cryptocurrency incentives) are designed to encourage fair behavior, malicious users may attempt to exploit the system if the potential gain outweighs the risk. Common malicious strategies include:

Transaction censorship: Ignoring transactions from specific users, nodes, or regions.
Secret alternative chains: Creating an altered chain in secret and publishing it once it is longer than the legitimate chain, undermining the tamper-evident and tamper-resistant properties.
Block withholding: Refusing to transmit blocks to other nodes, disrupting information distribution (mitigated in highly decentralized networks).

This section highlights that while blockchain technology offers strong protections and transparency, interfacing with the real world, human factors, and cybersecurity risks still require careful governance and monitoring.

9. Limitations and Challenges of Blockchain Networks

9.1 Malicious Users and Network Administrators

While malicious users can cause short-term disruptions, blockchain networks can perform hard forks to mitigate their impact. Whether damages—such as lost funds—are reversed depends on the developers and community consensus.

In permissioned blockchain networks, infrastructure administrators may also act maliciously. Depending on the system configuration, administrators could potentially:

Take over block production.
Exclude certain users from transactions.
Rewrite block history or double spend coins.
Delete resources or disrupt network connections.

9.2 Trust Misconceptions

A common misconception is that blockchain networks are completely “trustless.” While there is no single trusted third party in permissionless networks, trust still exists in several areas:

Cryptographic integrity: Algorithms and implementations must be secure and error-free.
Smart contract correctness: Contracts must function as intended without loopholes.
Developer reliability: Users rely on developers to produce bug-free software.
Majority behavior: Users trust that no single entity controls more than 50% of block creation power.
Node behavior: Users not running full nodes trust other nodes to process transactions fairly.

Permissioned networks rely on administrators to grant access and enforce trust, but this centralization introduces different trust considerations.

9.3 Resource Usage

Blockchain networks achieve security and consensus through resource expenditure:

Proof of Work (PoW): Uses “hard to solve, easy to verify” computational puzzles.
- Ensures that no node can dominate block creation.
- However, PoW consumes vast amounts of electricity. For example:
  - Bitcoin is estimated to use electricity comparable to the entire country of Ireland.
  - Projections suggested it could rival Denmark’s electricity consumption.
Full node synchronization: Downloading the entire blockchain (e.g., Bitcoin’s blockchain exceeds 175 GB) consumes significant bandwidth and storage.

Permissioned networks often employ less resource-intensive consensus mechanisms due to higher trust among participants.

9.4 Inadequate Block Publishing Rewards

A critical challenge for blockchain sustainability is adequate incentives for publishing nodes.

High computational requirements and volatile cryptocurrency prices may make block publishing unprofitable.
Insufficient rewards can lead to:
- Delays in publishing blocks and processing transactions.
- Reduced confidence in the cryptocurrency’s reliability.
- Increased vulnerability to attacks by well-resourced malicious actors.

9.5 Public Key Infrastructure and Identity

Blockchain networks use public key cryptography, but this does not inherently provide identity management:

Users can have multiple private keys.
A single public key can generate multiple addresses.
Blockchain signatures link transactions to private keys but not to real-world identities.
Any association between blockchain addresses and real identities relies on external processes, not the blockchain itself.

This distinction is important for applications like identity verification, regulatory compliance, and KYC (Know Your Customer) systems.

This section highlights that while blockchain technology provides robust security, decentralization, and tamper resistance, practical limitations—including trust assumptions, resource consumption, incentives, and identity challenges—must be carefully managed for successful implementation.