Quantum computers could eventually break widely used cryptographic systems such as RSA and ECC. Post-quantum cryptography introduces new algorithms that run on ordinary computers but are designed to remain secure against both classical and quantum attacks.
Pritthish Nath
For decades, the security of the Internet has depended on mathematical problems that are extremely difficult for ordinary computers to solve.
When you connect to a website over HTTPS, cryptographic algorithms help establish a secure connection, verify the server's identity, and prevent attackers from reading the traffic.
A large part of this infrastructure relies on algorithms such as RSA and elliptic-curve cryptography (ECC).
The problem is that sufficiently powerful quantum computers could potentially break the mathematical assumptions behind these algorithms.
Normal computers process information using bits that are either 0 or 1.
Quantum computers use qubits, which can exploit quantum mechanical properties to perform certain types of computation very differently.
One particularly important algorithm is Shor's algorithm.
A sufficiently powerful quantum computer running Shor's algorithm could efficiently solve problems such as integer factorization and discrete logarithms—the foundations behind RSA and many elliptic-curve systems.
That doesn't mean today's quantum computers can break HTTPS.
They can't.
The concern is what happens when sufficiently capable machines eventually exist.
There is another problem known as "harvest now, decrypt later."
An attacker doesn't necessarily need to decrypt encrypted traffic today.
They can capture encrypted communications and store them:
Today
Encrypted traffic
↓
Attacker captures it
↓
Stores it for yearsIf quantum computers become powerful enough in the future, that attacker could potentially go back and decrypt some of the information they collected.
This matters particularly for information that needs to remain confidential for many years, such as government records, financial information, intellectual property, and sensitive communications.
So waiting until quantum computers become capable of breaking existing cryptography could be too late.
An interesting part of the solution is that you don't need to put a quantum computer inside every server.
Instead, cryptographers are developing post-quantum cryptography (PQC).
These are cryptographic algorithms that run on ordinary computers but are designed to resist attacks from both classical and quantum computers.
Some of the major standardized algorithms include:
ML-KEM — used for establishing shared encryption keys.
ML-DSA — used for digital signatures.
SLH-DSA — another post-quantum digital signature scheme.
These algorithms provide new mathematical foundations for cryptographic protocols such as TLS.
There are actually two different problems that need to be solved.
Encryption asks:
Can someone else read this communication?
Authentication asks:
Can I trust that I'm communicating with the legitimate server?
Imagine visiting:
https://example.comYour browser needs to establish an encrypted connection, but it also needs to make sure that the server really is example.com.
Digital signatures are heavily involved in this process.
Therefore, simply replacing encryption algorithms isn't enough. The Internet also needs to migrate its authentication and digital-signature infrastructure.
This isn't purely a theoretical research project anymore.
Browsers, operating systems, cloud providers, CDNs, and networking software are beginning to introduce post-quantum cryptography.
One common approach is hybrid cryptography.
Instead of immediately replacing existing algorithms, systems can use both classical and post-quantum mechanisms:
Classical cryptography
+
Post-quantum cryptography
↓
Secure connectionThis provides protection against quantum attacks while maintaining compatibility with existing infrastructure.
Large infrastructure providers are already deploying these technologies at Internet scale.
Replacing a cryptographic algorithm isn't as simple as changing one line of code.
The Internet contains an enormous amount of legacy infrastructure.
Consider just one HTTPS connection:
Browser
↓
Operating system
↓
TLS library
↓
Network
↓
CDN / Load Balancer
↓
Web Server
↓
ApplicationEvery layer may contain cryptographic dependencies.
And the same problem exists in:
VPNs
SSH
email encryption
certificates
cloud infrastructure
APIs
databases
mobile applications
embedded devices
hardware security modules
authentication systems
Some devices may remain in production for 10, 15, or even 20 years.
Those systems need to be considered long before quantum computers become powerful enough to attack them.
Post-quantum algorithms aren't necessarily drop-in replacements with identical characteristics.
Some have larger keys, signatures, or handshake messages than their classical counterparts.
That can increase:
bandwidth usage
memory requirements
CPU usage
handshake sizes
storage requirements
For an individual website, these differences might be insignificant.
At the scale of billions of Internet connections, however, even small changes can become significant engineering considerations.
Most application developers won't need to implement post-quantum cryptography themselves.
That's a good thing.
Cryptographic primitives are notoriously difficult to implement correctly, and application developers should generally rely on well-tested libraries and infrastructure.
Instead, developers should pay attention to the cryptographic dependencies underneath their applications.
For example:
Application
↓
TLS library
↓
Operating system
↓
Cloud / CDNAs those layers gain PQC support, applications can benefit without implementing the cryptography themselves.
For systems that store highly sensitive information for long periods, however, the migration becomes much more important.
The interesting thing about post-quantum cryptography isn't simply that quantum computers might break RSA.
The more interesting problem is the scale of the migration.
The Internet has billions of devices and services that depend on cryptographic algorithms developed decades ago.
Replacing those algorithms while keeping everything interoperable is a massive infrastructure project.
And that's why post-quantum cryptography is being treated less like a distant research topic and more like a long-term engineering migration.
The quantum computer capable of breaking today's cryptography may still be years away.
The migration to protect against it has already begun.
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