Bitcoin's Quantum Challenge: Why I Built a Post-Quantum Blockchain from Genesis

I started building Lattica in January 2026 because I wanted to understand how cryptocurrencies and blockchains actually work by building one myself.

At the beginning, my goal was not to create a post-quantum blockchain. I wanted to explore blockchain technology from the inside.

I started with my own codebase and experimented with different approaches:

custom Proof-of-Work designs;
mining implementations;
peer-to-peer networking;
different blockchain architectures;
different cryptographic components.

During this process, I studied Bitcoin deeply — its architecture, consensus model, transaction system, and security assumptions.

I also explored cryptographic hashing in depth. I built a C/CUDA toolkit for differential analysis of reduced-round SHA-256 and independently reproduced the published collision results at 23, 28 and 38 steps. This research helped me better understand the design and limitations of cryptographic primitives, and influenced my decision to use SHA3-256 (Keccak) as the hashing foundation for Lattica.

Full reproduction and measurement study: https://github.com/Kristian5013/sha256-cas

After many experiments, I reached an important conclusion:

Building a secure decentralized blockchain from scratch is much harder than it first appears.

A blockchain is not just code. Every component depends on the others: consensus, transaction validation, networking, wallets, cryptography, and security assumptions must work together.

Eventually, I chose the Bitcoin Core architecture as the foundation because it represents one of the most tested blockchain designs ever created.

Lattica uses:

UTXO ledger;
Script-based transactions;
full-node validation;
peer-to-peer networking;
Proof-of-Work consensus.

But I wanted to explore a different question:

What would a blockchain look like if post-quantum security was not added later, but designed from the very first block?

While adapting a Bitcoin-like architecture, I studied the challenges of replacing elliptic-curve cryptography with post-quantum alternatives.

I realized this is not simply an algorithm replacement.

It affects:

key management;
transaction structure;
wallet design;
validation rules;
network communication;
ecosystem compatibility.

A blockchain is a living system built on shared assumptions.

This led me to build Lattica — a new blockchain designed for the post-quantum era from genesis.

Lattica uses:

ML-DSA-44 (FIPS 204) for quantum-resistant signatures;
ML-KEM-768 (FIPS 203) for encrypted peer-to-peer transport;
SHA3-256 / SHA3-256d (FIPS 202) for hashing and Proof-of-Work;
no elliptic-curve cryptography in the codebase.

That last point is the one I would ask you to check rather than believe:

Code:

git clone https://github.com/lattica-core/lattica && cd lattica
git ls-files | grep -c secp256k1     # -> 0

Many projects described as quantum-resistant introduce post-quantum signatures alongside existing elliptic-curve systems. For Bitcoin that is unavoidable — millions of coins sit behind published curve keys that no authority can move, so any workable proposal is additive. Lattica made the substitution while it was still cheap, which is one of the advantages a new chain can have.

The mainnet launched on 11 July 2026 after months of development.

Current limitations, stated up front:

no independent security audit of the integration (the ML-DSA-44 and ML-KEM-768 implementations are PQClean, reviewed upstream);
the chain is three weeks old — design arguments are not a substitute for having survived attack;
the P2P handshake is encrypted but unauthenticated, the same posture as Bitcoin's own v2 transport;
no migration path for existing coins, by design;
signatures are large, which makes hardware-wallet and light-client support harder than usual.

This project is not an attempt to replace Bitcoin. Bitcoin's conservative approach is one of the reasons it has remained secure.

Instead, Lattica explores another question:

What could a blockchain designed for the post-quantum era look like if security was built in from the beginning?

Technical documentation:

Whitepaper: https://lattica.org/whitepaper/
One-page overview: https://github.com/Kristian5013/lattica/blob/main/doc/overview.md
Post-quantum comparison: https://github.com/Kristian5013/lattica/blob/main/doc/post-quantum-chains.md
SHA-256 cryptanalysis toolkit: https://github.com/Kristian5013/sha256-cas
Explorer: https://explorer.lattica.org
Source code: https://github.com/Kristian5013/lattica

Feedback from researchers, cryptographers, and blockchain developers is welcome.