What is HNDL Attack? Hackers are Shopping Your Data
Today, the vast majority of enterprises utilize encryption to protect their core asset: data. Countless pieces of information traversing the internet—ranging from customer privacy and corporate financial records to state secrets—are locked with complex mathematical algorithms. Because breaking these locks and peering inside would take tens of thousands of years with current technological capabilities, we transmit our data with peace of mind.
However, cyber threat actors are already looking far into the future and executing a new strategy: even if it is encrypted text that cannot be opened right now, they harvest and store it all anyway. This type of threat is called an HNDL (Harvest Now, Decrypt Later) attack.
Let’s look into why hackers are currently “shopping” for encrypted data as if filling a cart at a supermarket, and what the countermeasures are.
Steal Now, Open Later: The Essence of the HNDL Threat
The core of HNDL attacks stems from the premise that current encryption technologies cannot remain secure forever. The reason hackers spend time and money to collect encrypted text that they cannot even crack today is precisely due to the advent of quantum computers.
Once quantum computers—which can solve decryption calculations in just minutes that would take supercomputers hundreds of years—become commercially viable, standard cryptographic systems widely used worldwide today (such as RSA) will be neutralized instantly. Hackers have already calculated that when the era of full-scale quantum computing arrives, they can pull out the encrypted data they stole and stored in the past and decrypt it with ease.
This attack method does not cause immediate damage like ransomware that disrupts corporate systems or demands money on the spot. In fact, many organizations remain completely unaware that their data has even been leaked. However, the moment the encryption is cracked down the line, a company’s core technologies or confidential information with long-term value will be completely exposed to hackers.
Data That Remains Fatal Even If Opened 10 Years Later
Some organizations or security professionals may ask, “Commercial quantum computers are still a long way off, so why worry already?” or optimistically assume, “If data is only decrypted years from now, it will lose its value by then.” However, the lifecycle of data is much longer and more potent than one might think.
- Military secrets directly linked to national security
- Mid-to-long-term corporate business strategies and proprietary source technologies
- Individuals’ unique medical records or financial histories
These types of data can still inflict fatal blows on enterprises and society even if exposed 10 years or more into the future. This is precisely why global security agencies are already establishing new cryptographic standards and rushing their implementation to prepare for quantum computer attacks that have not yet fully materialized. When it comes to security, starting only when a threat becomes a reality is already too late. Especially for a threat like HNDL that accumulates over time, it is no exaggeration to say that a company’s current level of security determines its future.
Overhauling Data Security Frameworks and the Importance of Key Management
How, then, should we respond to this invisible “encrypted data shopping” attack? To ensure hackers cannot open the encrypted data even if they steal it, we must transition our underlying algorithms to Post-Quantum Cryptography (PQC)—a next-generation cryptographic system that cannot be breached even by quantum computers.
In addition, a core element that is often overlooked is cryptographic key management. No matter how strong a defensive shield you build, if the keys required for data decryption are stored insecurely, hackers can simply steal those keys to open the data without ever needing to crack complex encryption. Data security in the quantum computing era depends not only on applying advanced encryption algorithms but also on how securely those cryptographic keys are generated, stored, and periodically rotated.
A Realistic Alternative for Implementing Quantum Security Without Full System Replacement
One of the main reasons many companies hesitate to adopt quantum security is the massive cost and the risk of operational downtime. Because the systems of financial, public, and private enterprises are organically intertwined atop legacy cryptographic systems, replacing them all at once is practically impossible.
The most realistic alternative proposed to solve this dilemma is a hybrid cryptographic architecture. This approach maintains the stably running legacy cryptographic systems while layering and concurrently operating Post-Quantum Cryptography on top of them. This allows organizations to flexibly introduce next-generation security systems without changing the interfaces or architecture of active systems at all, enabling a secure migration without disrupting business continuity.
Penta Security’s Data Protection Architecture for the Quantum Computing Era
Penta Security, a cryptography-based security specialist, has fully integrated both global standard PQC algorithms for digital signatures and key exchange (Dilithium, Kyber) into its cryptographic modules. This establishes a robust response system that allows enterprises to navigate the cryptographic transition period without confusion. Its encryption platform, D.AMO, supports the holidays hybrid cryptographic architecture mentioned above, helping companies transition to a quantum security system gradually and flexibly without the burden of completely replacing existing infrastructure.
To maximize the effectiveness of encryption, seamless key management via a cryptographic key management system is essential.
- D.AMO KMS is a key management platform that securely and integrally manages the entire cryptographic key lifecycle, from generation to destruction. It fundamentally eliminates the risk of key leakage by physically separating encrypted data from cryptographic keys and thoroughly controlling them from a centralized location.
- Notably, it supports not only legacy cryptographic key management functions but also integrates QKMS (Quantum Key Management System) functionalities tailored for quantum security environments. Through this, it seamlessly interoperates with advanced quantum security technologies—such as Post-Quantum Cryptography, Quantum Random Number Generation (QRNG), and Quantum Key Distribution (QKD)—safeguarding the integrity of cryptographic keys amid a rapidly evolving threat landscape.
Robust encryption and key management are the most definitive preventive measures to effectively neutralize hackers’ “harvest now, decrypt later” strategy. Investment in security to protect future business continuity and customer trust must begin today.
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