Is quantum really "about" to destroy blockchain? What you need to know right now

A question asked many times: Does blockchain need to panic before the quantum threat? The answer is more complex than you think, because not all blockchains face the same level of risk.

The “store and decode” attack is the real issue

When it comes to quantum, people often imagine it as an attack happening in the future. In reality, the greatest danger has already occurred today.

Attackers don’t need a super-powerful quantum computer. They are storing encrypted communications now, with the intention of decrypting them when technology allows. The way modern algorithms calculate the number of links in cryptographic algorithms mainly relies on the difficulty of integer factorization—a problem that quantum computers can solve quickly using Shor’s algorithm.

What does this mean? Any sensitive or classified information transmitted today could be exposed in 10-50 years. Therefore, blockchain systems that need to protect long-term data must start transitioning to quantum-resistant encryption right now.

Digital signatures: A completely different issue

Many people mistakenly treat digital signatures (like ECDSA, EdDSA) as having the same risk level as traditional public key encryption.

Simply because signatures do not contain “private content that quantum computers could decrypt.” They only verify the authenticity of a current transaction. Even if quantum computers could forge signatures in the future, old signatures on the blockchain cannot be “erased”—quantum computers cannot go back in time.

Result: signatures need upgrading, but not immediately. Completed and verified transactions will remain secure.

zkSNARKs: An unexpected layer of protection

Zero-Knowledge Proof technology (like zkSNARKs) operates on a completely different principle. Although they currently use elliptic curves, their zero-knowledge property does not reveal personal data in proofs.

This means zkSNARKs are unaffected by the quantum decryption capability, because there is nothing to decrypt.

Practical priority order for blockchain

To summarize the urgency:

1. Encryption for private communications (needs immediate)
2. Digital signatures (can wait but are necessary)
3. zkSNARKs (least urgent)

However, Bitcoin is a notable exception. Bitcoin is not threatened by an imminent quantum attack, but by legacy design decisions.

In its early days, Bitcoin used a P2PK structure, where public keys are directly published on the chain. Quantum computers could use Shor’s algorithm to extract private keys from these public keys. Additionally, wallets that are inactive or have lost keys will never be able to update, leaving millions of BTC vulnerable to permanent attack.

Moving Bitcoin is not just a technical challenge—it involves legal, social cooperation, and time. Bitcoin needs to plan now, but implement gradually.

Warning: Rushing updates could do more harm than good

An important note: many current post-quantum algorithms come with significant costs. Post-quantum signatures (ML-DSA, Falcon) are 10 to 100 times larger than current signatures and can be vulnerable through side channels or implementation errors.

Even algorithms once considered secure, like (Rainbow, SIKE), have been broken. Therefore, blindly rushing to update introduces risks greater than the threats they aim to mitigate.

Practical strategy for blockchain

Instead of a full overhaul, blockchain should adopt a multi-layered approach:

• Hybrid encryption: Combining post-quantum + classical for long-term secure communications
• Early hash signatures: For cases with less signing needs (firmware updates)
• Modular design: Allowing future signature system upgrades without compromising historical assets on the chain
• Synchronization: Monitoring Internet PKI standards and proceeding cautiously

Quantum is a real challenge, but not a reason to panic today. It’s a reason to plan carefully starting now.