White Box Cryptography - Everything You Need to Know

Protecting sensitive data has become more challenging than ever. Traditional encryption methods work well in secure environments, but what happens when attackers have full access to the system? That’s where white box cryptography comes in.

White box cryptography keeps cryptographic keys safe, even when an attacker can see and manipulate the software. Unlike standard encryption, which assumes the system is secure, this approach makes it nearly impossible for hackers to extract or misuse cryptographic keys. This blog will explain how it works, why it matters, and where it’s used.

What is white-box cryptography?

Whitebox cryptography is a powerful solution that protects secret keys from disclosure in software implementations. It is essentially a way of protecting software implementations of different cryptographic algorithms from other types of vulnerabilities.   

Whitebox cryptography combines encryption and obfuscation methods to embed secret keys in application code. The aim is to combine code and key so that an attacker cannot distinguish between the two, and the new "white-box" program can be safely executed in an insecure environment.  

Why does white-box cryptography matter?

White-box cryptography helps maintain the confidentiality of cryptographic keys in hostile environments. 

Traditional encryption methods are vulnerable to key extraction attacks where attackers have compromised the system and can analyze the software. White box cryptography, however, provides an unyielding defense against such attacks, ensuring the keys remain secure even under adverse conditions.

How does white-box cryptography work?

White box cryptography employs various techniques to obfuscate cryptographic keys, rendering them virtually indistinguishable from other data within the software. This is achieved through code obfuscation, mathematical transformations, and other sophisticated methods.

By embedding the cryptographic keys deep within the software and obscuring their structure, white box cryptography ensures that even if attackers can see and manipulate the code, they cannot readily identify or extract the keys.

In this model, the attacker has complete control over the execution environment of the targets, assuming that: 

• Fully privileged attacks have full access to the deployment algorithms. 
• The dynamic execution can be observed, and important data, such as cryptographic keys, can be viewed. 
• Detailed system algorithms are fully visible and modifiable. 

To successfully hide the keys in this scenario, according to Brecht Wyseur, we can take the following steps when we try to white-box a block cipher:  

Partial evaluation

When executing a trade, we modify the trade based on the key code. For example, in the replacement phase of a block cipher, we would change the look-up table to be key-dependent. Note that someone seeing this table could infer the key.  

Tabularization

It transforms all other operations to use look-up tables, which can describe any function.  

Randomization and delinearization

We create an encoded sequence of look-up tables with the same functionality as the original string but hide the key. With this new string, we now have a disguised algorithm. 

Advantages of white-box cryptography

1. Unparalleled security

   Security is where white-box cryptography truly excels. It keeps cryptographic keys safe even when attackers have compromised the environment, making it perfect for protecting sensitive data in hostile settings.

2. Adaptability

   The technology adapts beautifully to different situations. It can be tailored to virtually any platform or application, giving organizations great flexibility.

3. Seamless integration

   When it comes to implementation, white-box cryptography fits right in with existing software. Organizations can add it to their systems without turning everything upside down, which makes adoption remarkably straightforward.

Challenges of white-box cryptography

1. Technical complexity

   Getting white-box cryptography up and running takes serious know-how. You need deep technical expertise to implement it properly, which can be a real stumbling block for some organizations.

2. Performance considerations

   There's a trade-off with performance. While traditional encryption might be a bit faster, White Box Cryptography adds some overhead. It's usually not a big deal, but you'll want to think twice if speed is absolutely critical.

3. Continuous evolution

   The security landscape never stands still. Attackers constantly develop new tricks, and defenders constantly develop new protections. Staying on top of these changes is a constant challenge.

White-box vs. gray-box vs. black-box cryptography

The attack contexts for the crypto module can be divided into black-box, gray-box, and white-box attacks.

The white box attack is considered the strongest, and the opponent has all privileges and access to the algorithm's implementation and dynamic execution.  In this model, the attacker has full access to the internal status.

The white box model is intended for the algorithm to run as software on the attacker's computer.   

In the "gray box" model, the attacker also has access to partial information from the side channel, which is where performance analysis comes into play.

In the “black box” model, the security of a cryptographic algorithm is examined. With symmetrical encryption, for example, the attacker can access a “device” that executes the encryption algorithm with a specific key.

White-box cryptography has proven to be more suitable than black-box and gray-box cryptography. 

Uses of white-box cryptography in applications 

In most cases, white-box cryptography is implemented to protect cryptographic implementations in various applications running on open devices such as smartphones, PCs, and tablets when the developer needs to achieve the highest level of security without relying on secure hardware elements. 

Various software applications store and process private and confidential data and can benefit significantly from white-box cryptography. In some industries, it is an integral part of your security policy. Some of the specific application examples are discussed below.  

1. Contactless payments with NFC  

Today, several mobile payment applications use Near Field Communication (NFC) technology to turn conventional phones into contactless payment terminals. These can be crucial for companies, especially those with limited resources, to invest in specialized point-of-sale systems. However, one of the main issues here is still security.

2. Medical applications 

Most data on medical devices is encrypted and sent using strong encryption. In addition, this medical data can be signed to ensure its integrity.

Usually, a key is safe within the confines of a medical device and on both cloud servers. Applications or programs running on your smartphone or desktop PC are the weakest links in terms of security.  

In this case, white-box cryptography helps secure both the decryption and the signing of keys, guaranteeing the security of medical data/records against theft or manipulation by attackers.  

3. OTT platforms 

The rapid rise of OTT, or above-ground video services, has led those in charge to protect video from hackers while ensuring easy access and a user-friendly experience: streamlined display for paying customers. It applies to both applications and set-top boxes OTT service providers use to provide content.

4. Secure digital signatures

Digital signatures are normally used for security as they facilitate undeniable user consent, even for remote entity authentication. In Europe, electronic signatures must have signing keys embedded into a trusted piece of hardware, such as certified smart cards, until 2016. Now, digital signatures are legalized, and any trusted hardware is not required. 

Initiatives like these have opened avenues for software-only signature generation for remote access control, contract signing, etc. 

Adopting the white-box approach to digital signatures will protect all parties involved against identity theft and voluntary sharing of access rights.

How does white cryptography prevent reverse engineering?

Reverse engineering has many practical uses in software development, including identifying underlying security issues. However, hackers also use it for malicious practices, such as malware and security breaches.

Whitebox cryptography resists reverse engineering threats by preserving code with cryptographic keys. It can be used to create reverse engineering detection tools and anti-tamper technology to prevent app reverse engineering. 

Conclusion

Whitebox cryptography is an excellent solution for protecting against various application vulnerabilities. Although there is still much room for improvement, it has shown great potential in protecting various applications from hackers. 

FAQs

1. What common cryptographic feature is an aspect of white-box cryptography where keys are protected from extraction when controlled by the penetration tester or attacker?

The keys are protected from extraction with obfuscation.

2. How secure is cryptography?

Cryptography helps authenticate senders and recipients to one another and protects against repudiation. Moreover, it can ensure the confidentiality and integrity of both data in transit and at rest.