Is post quantum encryption an emerging threat?

Date: December 29, 2025

Source: Core Insights Advisory Services

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Post Quantum Encryption is not an emerging threat itself, but rather a necessary response to an emerging threat posed by quantum computing. The real threat comes from the potential of future quantum computers to break widely used cryptographic algorithms that secure digital communications and data today.  These algorithms, such as RSA, Elliptic Curve Cryptography (ECC), and Diffie-Hellman, rely on mathematical problems—like integer factorization and discrete logarithms—that are computationally hard for classical computers but could be efficiently solved by a sufficiently powerful quantum computer using Shor’s algorithm.  This capability would allow an adversary to decrypt sensitive information, forge digital signatures, and compromise the confidentiality and authenticity of data.

The urgency is heightened by the "harvest now, decrypt later" (HNDL) strategy, where malicious actors are already collecting and storing encrypted data today with the intent to decrypt it once quantum computers become capable of breaking current encryption standards.

This means that data protected by today’s asymmetric cryptography—such as financial records, personal communications, and national security information—could be compromised in the future, even if it is currently secure.  Experts estimate that cryptographically relevant quantum computers (CRQCs) capable of executing these attacks could emerge within the next 5 to 15 years, with some predictions suggesting breakthroughs as early as 2028.  As a result, the transition to post-quantum cryptography is critical and must begin now to avoid widespread security failures.

Post-quantum cryptography addresses this threat by developing new cryptographic algorithms based on mathematical problems believed to be resistant to both classical and quantum attacks.

These include lattice-based, hash-based, code-based, and multivariate polynomial cryptography.  For example, NIST has standardized algorithms like ML-KEM (based on lattice cryptography) for key encapsulation and ML-DSA for digital signatures, which are designed to withstand quantum attacks.  While symmetric encryption like AES remains relatively secure—especially AES-256, which only has its effective security halved by Grover’s algorithm—its long-term viability is still a concern, and the focus is on replacing vulnerable asymmetric systems.  Therefore, the emergence of post-quantum cryptography is a proactive defense mechanism to ensure data security in a future where quantum computing may render current encryption obsolete.

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Source: NIST

What Is Post-Quantum Cryptography?

Researchers worldwide are racing to develop new devices called quantum computers, which could do many things conventional computers cannot — including breaking the defenses that secure confidential electronic information. NIST is leading a global effort to create electronic defenses against such attacks through its Post-Quantum Cryptography (PQC) project, which released the first three finalized PQC standards in 2024. Read on for some answers to common questions about this developing technology and NIST’s efforts.

What are post-quantum encryption algorithms? 

Encryption algorithms protect confidential electronic information, from email messages to medical records and financial statements, from unauthorized viewers. For decades, these algorithms have proved strong enough to defend against attacks using conventional computers that attempt to defeat the encryption. However, a new type of device under development called a quantum computer could break these algorithms, rendering our electronic secrets vulnerable to discovery. 

To counter this looming threat, we need encryption methods that can stave off cyberattacks by both the conventional computers

we know today and the quantum computers of tomorrow. These new methods are called post-quantum encryption algorithms. 

What is quantum computing? 

A quantum computer draws upon different scientific concepts than a conventional computer does. It takes advantage of the quantum world’s counterintuitive properties — which enable a bit of data to act as both a 0 and 1 at the same time — to make calculations that would be difficult or impossible on a conventional computer. 

If they can be built, sufficiently powerful quantum processors would be able to sift through many potential solutions to a problem simultaneously, zeroing in on the correct answer very quickly. This sort of sifting is a task that conventional computers cannot do very quickly or efficiently.

Why are quantum computers being developed if they can potentially cause so much harm?

There are many helpful things quantum computers will likely be able to do. Quantum computers have the potential to accomplish tasks that involve the interplay of complex variables. These tasks include drug design, simulations of complex molecules, and solutions to the classic “traveling salesman” problem — finding the most efficient route through a number of destinations. 

The quantum computing field remains in its infancy. Researchers must overcome major technical hurdles before they can build powerful quantum computers, and it is an open question as to how formidable quantum computers can become. However, advanced quantum computers remain a strong possibility, and they would have such a major impact on present-day encryption that the world must prepare for them.

How does current cryptography work, and how would a quantum computer crack it? 

Currently, many encryption algorithms rely on the difficulty conventional computers have with factoring large numbers. Sufficiently powerful quantum computers would not have this difficulty. 

Conventional cryptographic algorithms select two very large prime numbers — which are only divisible by 1 and themselves — and multiply them to obtain an even larger number. While multiplying the prime numbers is easy and fast, it’s far more difficult and time-consuming to reverse the process and figure out which two prime numbers were multiplied together, and that’s what a conventional computer would have to do to break this encryption. These two numbers are known as the “prime factors.” For large enough numbers, a conventional computer has been estimated to need billions of years to figure out these prime factors.

A sufficiently capable quantum computer, though, would be able to sift through all of the potential prime factors simultaneously, rather than one by one, arriving at the answer exponentially more quickly. Experts have begun referring to such a mature device as a “cryptographically relevant” quantum computer. Instead of billions of years, it’s possible a quantum computer could solve this puzzle in days or even hours, putting everything from state secrets to bank account information at risk.

Why do we need post-quantum encryption, and how will PQC algorithms work? 

To stave off attacks by a quantum computer — if and when a cryptographically relevant one is built — the worldwide community must retire current encryption algorithms. Post-quantum encryption algorithms must be based on math problems that would be difficult for both conventional and quantum computers to solve. 

The algorithms are designed for two main tasks for which encryption is typically used: general encryption, used to protect information such as passwords exchanged across a public network, and digital signatures, used for identity authentication. 

Of the four algorithms NIST has selected as the initial ones to be standardized, three are based on a family of math problems called structured lattices, while the fourth uses mathematical relationships known as hash functions. Instead of requiring a computer to factor large numbers, lattice and hash problems use other types of math that experts believe will be hard to solve for quantum computers and conventional computers alike.

Additional algorithms still under consideration are designed for general encryption and do not use structured lattices or hash functions in their approaches.

To put these algorithms into practice, NIST has led efforts to develop technical standards for post-quantum encryption. These standards aim to provide solutions for different situations, employ varied approaches for encryption, and offer more than one algorithm for each kind of application in the event one proves vulnerable.

When will a quantum computer appear that is powerful enough to threaten current encryption methods?

No one knows. Researchers need to surmount many technical challenges before this can happen. Experts’ estimates range from a few years to a few decades.

The basic unit of information in a quantum computer is called a quantum bit, or “qubit.” Qubits are quantum computing’s equivalent of a bit in a conventional computer. Quantum computers employing many thousands of qubits will be needed to break present-day encryption.

There is a fundamental problem: Qubits are fragile. The slightest disturbances can corrupt them and create errors before a quantum computer can successfully complete an operation, such as breaking an encryption code.

Researchers are experimenting with different technologies for making qubits. Each type has advantages and disadvantages, and nobody is sure which approach will end up working best — or if some other approach, yet to be discovered, will overtake them all.

Still, even though it’s not possible to predict exactly when — or even if — quantum computers will break present-day encryption, the potential threat is great enough that researchers are preparing for it now. 

If cryptographically relevant quantum computers don’t exist yet, why is developing post-quantum encryption algorithms important now? 

The world must plan ahead. Historically, it has taken a long time from the moment that a new algorithm is standardized until it is fully integrated into information systems. The process can take 10 to 20 years, partly because companies have to respond to the changes by building the algorithms into products and services we use every day.

No one knows how long it will take to build a cryptographically relevant quantum computer. Predictions vary widely, but some people think it may be possible in less than 10 years. 

Even if computer security experts implement post-quantum encryption algorithms before sufficiently powerful quantum computers are built, a lot of encrypted data remains under threat because of a type of attack called “harvest now, decrypt later.”

What is “harvest now, decrypt later”? 

Some secrets remain valuable for many years. Even if an adversary can’t crack the encryption that protects our secrets at the moment, it could still be beneficial to capture encrypted data and hold onto it, in the hopes that a quantum computer will break the encryption down the road. This idea is sometimes expressed as “harvest now, decrypt later” — and it’s one of the reasons computers need to start encrypting data with post-quantum techniques as soon as possible.