This post explains why INTcoin uses post-quantum cryptography and what it means for your coins.
The Problem
Every major cryptocurrency today — Bitcoin, Ethereum, Litecoin, Monero — uses cryptographic algorithms based on mathematical problems that quantum computers can solve efficiently.
ECDSA and EdDSA (used for signing transactions) rely on the difficulty of the Elliptic Curve Discrete Logarithm Problem. In 1994, Peter Shor published a quantum algorithm that solves this in polynomial time. A sufficiently powerful quantum computer running Shor’s algorithm can derive your private key from your public key.
Why it matters now: Every time you spend from a Bitcoin address, your public key is revealed on the blockchain. Even if quantum computers don’t exist today, that public key sits there permanently. A future quantum computer could retroactively derive the private key and steal remaining funds.
The Timeline
Nobody knows exactly when quantum computers will be powerful enough. Estimates range from 2030 to 2045+. But several things are clear:
- NIST finalised post-quantum cryptography standards in 2024 (FIPS 203, 204, 205)
- NSA has mandated migration to post-quantum algorithms for national security systems
- GCHQ recommends planning for post-quantum migration now
- The US government has set 2035 as a deadline for federal systems to complete migration
The consensus among cryptographers is: migrate now while there’s no urgency, rather than scramble later.
What INTcoin Does Differently
INTcoin doesn’t attempt to bolt quantum resistance onto an existing design. It replaces the entire cryptographic foundation:
Signatures: ML-DSA-87 (Dilithium5)
NIST FIPS 204, the highest security level (Level 5). Based on the Module-LWE lattice problem, which has no known efficient quantum attack. Your transaction signatures are secure against both classical and quantum computers.
Key exchange: ML-KEM-1024 (Kyber1024)
NIST FIPS 203. Every peer-to-peer connection begins with a Kyber key encapsulation, establishing forward-secret encryption. A passive observer — even one with a quantum computer — cannot decrypt past network traffic.
Hashing: SHA3-256
The SHA3 family is quantum-resistant by design. Grover’s algorithm provides only a quadratic speedup against hash functions, and SHA3-256 at 256 bits provides 128-bit security even against quantum search.
The Trade-offs
Post-quantum keys and signatures are larger than classical ones:
| ECDSA (Bitcoin) | ML-DSA-87 (INTcoin) | Ratio | |
|---|---|---|---|
| Public key | 33 bytes | 2,592 bytes | 79x |
| Signature | 72 bytes | 4,627 bytes | 64x |
This means INTcoin transactions are larger, blocks hold fewer transactions at the same size, and more bandwidth is needed for network communication. These are real costs, and the project addresses them through compression strategies, efficient encoding, and a 2-minute block time that provides adequate throughput.
The alternative — using small keys now and facing a catastrophic migration later — is worse.
What About Bitcoin?
Bitcoin would need a consensus-level fork to change its signature scheme. This is technically possible but politically and practically extremely difficult. Every wallet, every library, every hardware signer, every exchange integration would need to update simultaneously. The Bitcoin community has not reached consensus on how to approach this.
INTcoin doesn’t have this problem because it was built with post-quantum cryptography from the start. There is no legacy to migrate.