Quantum Computers Are Coming for Web3 Identity

By Malak Gandhi |
BTech CS (AI & ML),
ATLAS SkillTech University
If you’ve spent any time in the tech world lately, you’ve probably heard two major buzzwords: Decentralized Identity (DID) and Quantum Computing.
On one hand, Web3 enthusiasts are pushing for DID so we can finally own our digital identities instead of trusting centralized servers (which seem to get hacked every other week). On the other hand, physicists are warning us about "Q-Day"—the day quantum computers become powerful enough to crack the encryption securing the entire internet.
For my Semester IV CIA project at ATLAS SkillTech University, I decided to smash these two concepts together. I wanted to see if we could build a Decentralized Identity system on Ethereum that could actually survive a quantum attack.
Spoiler alert: The math works, but the blockchain is going to need a massive upgrade. Here is a breakdown of my experiment.
The Problem: Why Your Crypto Wallet is Vulnerable
Right now, networks like Ethereum and Bitcoin are secured by something called Elliptic Curve Digital Signature Algorithm (ECDSA). It’s fantastic technology for classical computers.
But quantum computers don't play by classical rules. Using something called Shor’s Algorithm, a functional quantum computer will be able to slice through ECDSA like a hot knife through butter. If we put our permanent digital identities on the blockchain today, a quantum hacker in the future could easily forge our digital signatures and steal our identities.
The Experiment: A Hybrid Approach
To tackle this, I built a two-part project:

1. The Application: I wrote a Decentralized Identity smart contract in Solidity and deployed it to the Ethereum Sepolia Testnet. This allowed users to register an ID and securely grant or revoke access to third parties.
2. The Quantum Benchmark: Because Ethereum can’t handle quantum-safe math natively yet, I simulated it off-chain. I wrote a Python script using the liboqs (Open Quantum Safe) library to benchmark standard ECDSA against CRYSTALS-Dilithium2—the new post-quantum standard chosen by NIST. I wanted to know: How much slower and heavier is quantum-safe math? I ran 1,000 iterations of both algorithms on my standard student laptop to find out. The Surprise: Speed Isn't the Issue Going into this, I assumed that quantum-resistant cryptography would be incredibly heavy and would fry my laptop's CPU. I was completely wrong. Lattice-based cryptography (like Dilithium) relies on matrix multiplication rather than complex scalar math. In my benchmarks, Dilithium actually verified signatures faster than traditional ECDSA (0.12 milliseconds vs. 0.35 milliseconds). CPU processing power will not be the bottleneck for the future of Web3. The Crisis: The "Data Bloat" Problem While the speed was great, the second metric I tracked revealed a massive, existential crisis for blockchain architecture. ● A standard ECDSA signature takes up 64 Bytes of data. ● A quantum-safe Dilithium2 signature takes up 2,420 Bytes of data. That is an increase of over 3,600%. If you know anything about Ethereum, you know that storing data on-chain is incredibly expensive, and blocks have strict size limits. If Ethereum were to force everyone to use Dilithium signatures today, the network would instantly bloat. Transaction fees (gas) would skyrocket, and the network would grind to a halt. What's Next? Building this project totally changed my perspective on the future of cybersecurity. Decentralized Identity is absolutely the way forward—nobody wants their sensitive data sitting on a vulnerable centralized server. But we cannot just blindly trust current blockchain infrastructure to protect us forever. To survive the quantum era, the Web3 space is going to have to figure out how to compress these massive quantum signatures, likely using technologies like Zero-Knowledge Proofs (ZKPs) or Layer-2 rollups. The quantum threat is real, but if we start upgrading our infrastructure now, we can stay one step ahead.