Free online consultation available. Please feel free to contact us.

Harvest attack (HNDL: Harvest Now, Decrypt Later)

Harvest attack (HNDL: Harvest Now, Decrypt Later)

This glossary explains various keywords that will help you understand the mindset necessary for data utilization and successful DX.

This time, we will explain the "risk of harvest attacks," which has been a frequently discussed topic and is the reason why post-quantum cryptography is still necessary even though quantum computers are not yet fully developed.

What is a Harvest Attack (HNDL: Harvest Now, Decrypt Later)?

A harvest attack (HNDL: Harvest Now, Decrypt Later) is a time-delay attack method in which data is collected and stored while encrypted at the present time, and its contents are decrypted at a later date.

Currently, countries around the world are urgently implementing countermeasures such as the introduction of post-quantum cryptography (PQC) to prepare for the threat of cryptography being cracked by quantum computers. This is because the risk of "harvest attacks" (HNDL: Harvest Now, Decrypt Later), which involve acquiring data now and decrypting it later, already exists in the future after quantum computers become practical.

It is sometimes referred to as "SNDL: Store Now, Decrypt Later" or "CNDL: Capture Now, Decrypt Later," which have the same meaning as "HNDL: Harvest Now, Decrypt Later," and is also academically described as "retrospective decryption."

*You can find an article with more details about post-quantum cryptography here.
⇒ Post-Quantum Cryptography (PQC) / Quantum Computer / Cryptogility / Harvest Attack | Glossary

Why we must prepare for the threat of quantum computers right now.

Knowing about the risk of cryptographic decryption through "harvest attacks" is crucial for correctly determining what security measures need to be taken and prioritizing them appropriately.

The age of quantum computers is still far off, so why is there so much excitement?

At least as of this writing, quantum computers are becoming increasingly popular, but it is still considered to be some time away from their full-scale practical application.

We should assume that the era when the personal computers and smartphones we use every day possess quantum computing capabilities is still some time away. Even if we consider something like a national-level supercomputer requiring massive investment, I think it's more accurate to say that "sufficient practical application is still some time away."

Although quantum computers are still in the research and development stage, you've probably been hearing a lot lately about the need to "prepare now for the threat of cryptography being broken by quantum computers."

You might think that we're making too much of a fuss when practical application is still a long way off. Or perhaps, while it might be understandable in areas like national security, it seems like an overreaction and a low-priority issue for most of us. However, the truth is that for many people, the risk of future cryptography and information leaks by quantum computers already exists, and we are being forced to make an immediate decision on how to deal with it.

"Harvest attack" risk

The risks of cryptography and data breaches by quantum computers that are already occurring are essentially these concerns. Alternatively, this type of "delayed attack" is called a "harvest attack."

  • You can "get" encrypted data right now.
    • For example, it's possible to capture data that will be circulating on the internet in 2026.
  • Even if you capture it, you cannot decipher it at this time.
  • However, if, for example, quantum computers become practical in 20 years, it will be possible to decipher data that was captured in the past at that point.

Certainly, the risks may not materialize in the immediate future. However, it is clear that we are actually in a situation where we are being forced to make an "immediate decision": "If we neglect to take countermeasures now, there is a possibility of serious consequences 10 or 20 years from now. What will we do?"

What kinds of accidents can happen?

If internet communications using public-key cryptography are intercepted, there is a high probability that they can be decrypted later. Similarly, data using digital signatures based on public-key cryptography may also be vulnerable to forgery of digital signatures at a later date.

The risk of decryption of general internet communications using public-key cryptography.

Specifically, public-key cryptography, which forms the foundation for secure and reliable communication over the internet, including "HTTPS communication in general," "VPN," and "remote desktop," may become vulnerable. If communication data is captured along the communication path by some means, there is a risk that its contents could be deciphered after quantum computers become practical.

For example, let's say you enter your credit card number when shopping online. Currently, it's protected by HTTPS (TLS) communication, so even if someone eavesdrops on the transmission path, there's no risk of data leakage. However, it's possible that it could be deciphered in the future.

Specifically, if the sum of "the period during which data must be protected" and "the period required to transition to secure new technologies" exceeds "the period until it is expected that the data will be decipherable by quantum computers," then it can be determined that the risk of harvest attacks should be considered immediately. Specifically, this is how it is considered:

  • X: The period during which data must be protected
  • Y: The time required to transition to a safe new technology
  • Z: The period until the expected time when "decryption by quantum computers becomes possible"

If "X + Y > Z" holds true, then there is clearly a risk of a harvest attack, and countermeasures are desirable (Mosca's theorem).

For example, let's assume that quantum computers will be able to decrypt them in 15 years. Credit card numbers are updated every few years, so their protection period is short, and by this standard, the urgency is not high. On the other hand, "personal information such as addresses and names" often remains unchanged throughout a person's life, so it is difficult to say that it would be okay if it were leaked after 15 years. In addition, data will only be securely protected again "after the countermeasures are completed," so if the transition is expected to take 3 years to complete, even if countermeasures are taken now, there will only be 12 years left after completion.

Similarly, if sensitive information is transmitted through services like VPNs or remote desktops, and someone captures the data along the communication path, there is a risk that the content could be leaked in the future.

The risk of electronic signatures being forged (related risks)

While not directly related to harvest attacks, another issue that could potentially lead to a major incident in the future if countermeasures are not taken now is the "risk associated with digital signatures."

As the long-used public-key cryptography becomes vulnerable, digital signatures may also be exposed to risks in the future. While decryption of communications targets communications that have been made in the past, digital signatures are expected to remain valid indefinitely. For example, a digital signature made 10 years ago is still expected to be valid, and a full-scale incident is possible.

The statement "I have electronically signed this contract" (a legal declaration of intent in digital data) is currently valid only because electronic signatures cannot be forged. However, after the practical application of quantum computers, it may become possible to alter the contents of a contract and re-sign it, rendering electronic signatures meaningless and potentially preventing the exercise of legal rights.

The blockchain of cryptocurrencies, such as Bitcoin, allows ownership of assets to be expressed through digital signatures. For example, a Bitcoin account number, or "address," is the public key itself. Therefore, if no countermeasures are taken (although countermeasures will likely be taken), the entire cryptocurrency system could collapse.

Symmetric-key cryptography (AES encryption) and hash functions are not significantly affected.

However, the practical application of quantum computers does not mean that all encryption methods are at risk of being broken. For example, the AES encryption method, which is widely used as a symmetric-key encryption method, is only expected to be affected to the extent that its key length is effectively halved. Therefore, it is thought that AES-256, which uses a 256-bit encryption key, will maintain sufficient security even after quantum computers become practical.

Similarly, it is believed that cryptographic hash functions (such as SHA-512), which are related technologies, will only be affected to the extent that they can be countered by using hash functions with a larger number of bits. Therefore, it is expected that the technologies most significantly affected by the advent of quantum computers will be those related to "public-key cryptography."

*This article provides a detailed explanation of what it means for "traditional public-key cryptography to become insecure" and what problems might arise in that situation.
​⇒Post-Quantum Cryptography (PQC) / Quantum Computer / Cryptogility / Harvest Attack | Glossary

Should we implement countermeasures against this?

To address the risk of harvest attacks, it is desirable to switch to "encrypted communication" and "digital signatures" using public-key cryptography, which is expected to remain secure even after quantum computers become practical. In other words, a transition to "post-quantum cryptography" is desirable.

As can be seen from the explanation so far, the risks associated with quantum computers have existed for a long time, but why has the need to prepare for the risks of quantum computers become a frequent topic of discussion recently? It is because concrete measures to mitigate these risks have become possible.

In August 2024, NIST, a US public institution, officially standardized post-quantum encryption methods such as "ML-KEM" (NIST Releases First 3 Finalized Post-Quantum Encryption Standards | NIST). This marked the beginning of concrete development of alternative technologies that would maintain security even after quantum computers become practical, making it possible to actually start implementing countermeasures. The risks themselves had existed for some time, but now that "new technologies with countermeasures have finally emerged and the time is ripe," it has become a topic of discussion for everyone to actually start working on countermeasures.

It is against this backdrop that governments around the world have begun to announce their aim to complete the transition by around 2035. In other words, we are now in a situation where society as a whole is expected to move forward with its response to post-quantum cryptography.

What we should do specifically

The first step we, as ordinary citizens, should take is to check what encryption technologies our company's IT products utilize, and what technologies are used for our company's encrypted data and digital signatures. Based on this information, we should then take appropriate measures, such as updating or replacing products with those that support post-quantum cryptography.

  • Creating a Crypto Inventory
    • List the encryption technologies used in the IT products your company uses.
    • Check what technologies are used for your company's encrypted data and digital signatures.
  • Take measures
    • Upgrading or switching to products that support post-quantum cryptography.
    • We will continue to replace our existing data and electronically signed documents with those protected by secure technologies.
    • Alternatively, if countermeasures are difficult, measures such as securely isolating the IT system from external sources, or ensuring that the electronic signature can be proven to have been made before the practical application of quantum computers, can be taken.
  • Enabling continuous response going forward (crypto-agility)
    • It is also desirable to be prepared for the possibility of discovering currently unknown vulnerabilities in post-quantum cryptography, and to have a system in place to quickly switch to "another secure cryptographic technology" in the event of such a problem.

Unlike traditional public-key cryptography, which has been used for many years and has a proven track record, post-quantum cryptography, which is expected to be widely used in the future, does not have sufficient usage history. Therefore, there is a risk that unexpected problems may be discovered later, rendering it unsafe to use as encryption, and it is said that we should prepare for such a possibility.

Furthermore, if your company is a provider of IT products, or uses an in-house developed IT system, the following may be necessary:

  • You need to take measures yourself (other companies won't do it for you).
    • An update will be released to support post-quantum cryptography.
    • We will continue to replace our existing data and electronically signed documents with those protected by secure technologies.
    • To prepare for the possibility of undiscovered technical vulnerabilities being discovered in post-quantum cryptography, we need to be prepared to switch to "another secure cryptographic technology" if something goes wrong.

Progress is steadily being made in addressing the IT usage environment of the general public (we may just be unaware of it).

Fortunately, progress is already being made in making post-quantum cryptography compatible software that many people use on a daily basis.

For example, the web browser "Chrome" has enabled post-quantum cryptography for HTTPS communication by default since version 124, released in May 2024, and "Firefox" has also started supporting it since version 132, released in October 2024.

For secure communication using post-quantum cryptography (TLS with ML-KEM) to actually occur during web browsing, in addition to support on the web browser side, "the cloud service or other communication destination also needs to support ML-KEM," but progress is being made in this area as well.

For example, even popular web servers like "Apache HTTP Server" and "Nginx" are becoming compatible by using newer versions of OpenSSL as "software to enable HTTPS communication."

Major cloud service providers are also making progress in addressing this issue; for example, AWS has begun implementing post-quantum cryptography support for its main services. Furthermore, since major services and software are already implementing such countermeasures, other software is increasingly being forced to comply.

file transfer middleware "HULFT" is also being improved to counter quantum cryptography.

Our proprietary file transfer middleware, "HULFT," has long been used as a de facto standard foundational product for secure, reliable, and safe data integration, primarily for use on mainframes and UNIX systems.
Our solutions have been used for many years in areas requiring the highest level of security and safety, such as mission-critical system, core system, and of course, we also implement robust countermeasures against quantum-resistant cryptography.

Although our products have a long history, we have always strived to adopt the latest technologies for safety and security. For example, we have long supported "AES encryption," which is the de facto global standard for symmetric-key cryptography (as mentioned above, AES encryption with a 256-bit key length is considered to maintain sufficient security even after the practical application of quantum computers), and we continue to improve our products to deliver the best possible safety and security.

As preparation for the quantum computing era, we will continue to use only technologies that maintain security, and we will take measures to address any unknown vulnerabilities found in existing cryptographic technologies. We will maintain a state where "the parts using HULFT are safe and reliable, and will not experience any problems."

For more information about file transfer middleware "HULFT", please click here.
⇒ HULFT Series | Services

Connecting technologies that make it easy to switch between cloud services and packaged software.

Even if you decide to "find and replace an alternative cloud service or packaged software" because your current product does not support post-quantum cryptography, "replacing what you are already using" is generally neither easy nor quick.

Data migration from existing systems is usually necessary, and preparing the necessary data conversion processes after ensuring data integration between the old and new systems often involves a great deal of effort.

Furthermore, it's not always possible to switch systems abruptly on a single day; if the migration involves a period of parallel operation, it will require even more effort and time.

Please utilize "connecting" technology

There are ways to efficiently develop these various "integration processes" using only a GUI. These are "connecting" technologies such as "DataSpider" and "HULFT Square," also known as "EAI," "ETL," and "iPaaS." By utilizing these, it is possible to smoothly and efficiently integrate old and new systems.

For more information about data integration software "DataSpider," please see here.
⇒ DataSpider Servista | Services

For more information about HULFT Square, a cloud service that enables you to "connect" things, please see here.
⇒ HULFT Square | Services

Related keywords (for further understanding)

Are you interested in "iPaaS" and "connecting" technologies?

Try out our products that allow you to freely connect various data and systems, from on-premise IT systems to cloud services, and make successful use of IT.

The ultimate "connecting" tool: data integration software "DataSpider" and data integration platform "HULFT Square"

"DataSpider," data integration tool developed and sold by our company, is a "connecting" tool with a long history of success. "HULFT Square," a data integration platform, is a "connecting" cloud service developed using DataSpider technology.

Another feature is that development can be done using only the GUI (no code) without writing code like in regular programming, so business staff who have a good understanding of their company's business can take the initiative to use it.

Try out DataSpider/ HULFT Square 's "connecting" technology:

There are many simple collaboration tools on the market, but this tool can be used with just a GUI, is easy enough for even non-programmers to use, and has "high development productivity" and "full-fledged performance that can serve as the foundation for business (professional use)."

It can smoothly solve the problem of "connecting disparate systems and data" that hinders successful IT utilization. We regularly hold free trial versions and hands-on sessions where you can try it out for free, so we hope you will give it a try.


Why not try a PoC to see if "HULFT Square" can transform your business?

Why not try verifying how "connecting" can be utilized in your business, the feasibility of solving problems using data integration, and the benefits that can be obtained?

  • I want to automate data integration with SaaS, but I want to confirm the feasibility of doing so.
  • We want to move forward with data utilization, but we have issues with system integration
  • I want to consider data integration platform to achieve DX.

Glossary Column List

Alphanumeric characters and symbols

A row

Ka row

Sa row

Ta row

Na row

Ha row

Ma row

Ya row

Ra row

Wa row

»Data Utilization Column List

Recommended Content

Related Columns

Recommended Articles