Secure Coding in Blockchain Development: Mistakes to Avoid

Writing smart contracts and blockchain apps that hold up under pressure isn’t just a nice-to-have. It’s the foundation for trust, functionality, and longevity. When developers cut corners or miss critical security steps, the consequences can be permanent and very public.

Whether you're a startup building your first dApp or an enterprise launching on-chain solutions, writing secure code should be baked into your process from day one.

At Shiv Technolabs, we’ve helped businesses avoid the most common pitfalls in blockchain development.

In this guide, we’ll cover the top mistakes developers often make while developing a blockchain app, why they matter, and how to avoid them.

Let’s get right into it.

Mistake 1: Writing Smart Contracts That Are Too Complex

If your smart contract feels like it’s trying to do 5 things at once, that’s already a red flag.

Smart contracts are hard to update. Once deployed, the code becomes part of the blockchain—and modifying it usually involves deploying a whole new contract. Complex contracts are harder to test, harder to audit, and more prone to bugs.

What you can do:

• Break logic into multiple smaller contracts with single responsibilities
• Use libraries like OpenZeppelin that are well-audited and trusted
• Document each module so future developers understand what it does

Simple isn’t just cleaner. It’s safer.

Mistake 2: Not Validating User Inputs

If you accept data from users or external systems, your app is vulnerable. A lot of smart contract exploits come from bad input handling—people passing weird values into functions and breaking the logic.

For example, imagine a token transfer function where a user inputs a negative value. Without validation, that might allow them to withdraw tokens they don’t even have.

Fix it by:

• Checking data types, limits, and boundaries for every input
• Using SafeMath or Solidity 0.8.x features that prevent overflows
• Rejecting suspicious inputs before they reach critical logic

Never assume users will “use it as intended.” Your code has to be ready for anything.

Mistake 3: Overlooking Reentrancy Risks

The DAO hack happened because of this exact issue. Here’s the short version:

A contract made an external call before updating its internal state. That opened a window for an attacker to make recursive calls and drain funds.

That’s what reentrancy means. And yes—it’s still a problem.

What helps:

• Always update your state variables before making external calls
• Add a lock mechanism like a reentrancy guard (OpenZeppelin has a good one)
• Keep your functions tight and clear, especially when dealing with transfers

Think of it like locking the door before answering a knock. Better safe than sorry.

Mistake 4: Forgetting Role Management

Who has access to what? It’s a question too many developers answer with, “the deployer account.” That’s not good enough.

If your app has functions like minting tokens, pausing transfers, or modifying logic, you need a clear access system.

Solutions:

• Use Ownable or AccessControl from OpenZeppelin
• Separate owner, admin, and user roles
• Log role changes so there’s a trail of who did what

Don’t hardcode your name as the admin. Future-you will thank you.

Mistake 5: Writing Gas-Heavy Code

Gas costs aren’t just a money issue. Expensive operations can make contracts unusable or vulnerable to attacks.

Let’s say your contract has a loop that grows as more users interact. At some point, it may become too expensive to execute, effectively locking users out.

Avoid that by:

• Avoiding unbounded loops
• Using mappings over arrays when possible
• Keeping storage reads and writes to a minimum

Write smart, efficient code from the beginning. Gas is part of the UX.

Mistake 6: No Upgrade Strategy

Code changes. Features evolve. Bugs show up.

But what happens when your smart contract is already deployed? Without an upgrade path, your only option might be to scrap it and redeploy everything. That’s not great for users, investors, or credibility.

Better approach:

• Use proxy contracts that separate logic and data
• Adopt patterns like Transparent Proxy or UUPS Proxy
• Document the upgrade process so it’s clear who can do what

Even if you don’t plan to upgrade now, you should prepare for the need later.

Mistake 7: Skipping Formal Testing

You’d be surprised how many contracts go live without proper tests. Even basic ones.

Blockchain apps deal with real assets. You can’t afford to “test in production.” Write tests for edge cases, bad inputs, and scenarios you think “could never happen.”

What to include:

• Unit tests for each function
• Integration tests across modules
• Simulated attack scenarios on testnets

Also, test under different gas limits, block sizes, and network conditions. Not all bugs are logic errors—some are environment-specific.

Mistake 8: Poor Documentation

Security isn’t just about code. It’s also about clarity.

If your team—or an auditor—can’t understand what a function does, they can’t evaluate its safety. Contracts without comments and documentation waste everyone’s time and leave you vulnerable to oversight.

Good docs include:

• Function summaries (what, not just how)
• Role and permission explanations
• Token or fund flow diagrams

Even small notes help. A few lines can make the difference between “we caught that” and “we missed it.”

Mistake 9: No External Code Review

Your internal team knows the code too well. That’s a problem.

Even the best developers overlook flaws in their logic. Bringing in external auditors provides a fresh perspective—and often reveals issues you hadn’t thought of.

Before launch:

• Hire a third-party blockchain auditor
• Fix or patch all critical issues before going live
• Consider a bug bounty program after deployment

Security is not a one-time checkbox. It’s a mindset.

Mistake 10: Relying Solely on Tools

Tools like Slither, MythX, or Echidna are useful. But they don’t replace human review.

Automated tools are good at finding known vulnerabilities. But they often miss complex logic errors, race conditions, or subtle economic exploits.

Use both:

• Let tools catch the obvious issues
• Have people test the real-world logic
• Always run both internal and external test reviews

Don’t let a clean report give you a false sense of security.

Final Thoughts

Blockchain development isn’t just about writing code that works. It’s about writing code that works safely, under stress, and out in the open.

Every line of code you write on the blockchain can impact money, users, and public trust. You don’t need to fear the risks, but you do need to respect them.

At Shiv Technolabs, we help companies build secure blockchain apps from the ground up. We focus on smart contract audits, gas efficiency, role management, and real-world testing to deliver products that are safe to use and built to last.

If you’re building on-chain, let’s make sure your code doesn’t just function—it holds up when it matters.