Would fragmenting data into several independent secured files would make a system Quantum-Resistant?

Question

In 2018 IBM is making available the first quantum computers.

This can be a disaster for most security systems based on computing power.

Could this type of scheme bring a solution to this problem ?

Fragmenting information as above.

Thanks in advance for your answers.

Regards,

Answer 1

It seems this scheme tries to secure the data by holding the encrypted data back until the user can prove to have legitimate access to it (knows the password). In this case, your main fear shouldn't be quantum computing but other vulnerabilities as they've been presented in the past.

Further, the claim that a propietary (encryption?) algorithm is used should raise suspicion since the algorithm can't be analysed by the public crypto community. One downside of it is that any statement about is quantum resitance is purely speculative, but let's create a potential scenario:

• The attacker somehow got access to the encrypted data (memory dumping or intercepting communication)
• The attacker does not know the key nor can abuse a flaw (in the firmware) allowing him to recover it
• Big quantum computers are accessible to the attacker

Then, we have to do some assumptions about the system deployed by Ex0-Sys:

• The data is encrypted using a symmetric cipher like AES
• The key for the file is stored seperately on the USB-Stick which can not be abused in our attack model

When the cipher used to encrypt the file turnes out to be secure, the best the attacker can do is using Groovers algorithm, recovering the key in $O(\sqrt{2^n})$ or $O(2^{n/2})$. Algorithms like AES-256 would then have 128-bit security, which is reasonably safe.

However, since a propietary algorithm is used, there is a non-negible probability that it is vulnerable to classical attacks like differential or linear cryptanalysis, so the attacker wouldn't need to own a quantum computer.

Last but not least, to answer the question in the title:

• Fragmenting the key would either no effect if an attack can be performed on the data itself.
• Fragmenting secret keys needed to recover another key used for the symmetric cipher (typical hybrid scheme) may or may not be strengthen by fragmentation depending on the asymetric cipher used.
• Fragmenting the data into $n$ pieces would require the attacker to aquire them all and find $n$ keys if he wanted the whole data or the data is mixed up in a way requiring the attack to have all $n$ parts to recover it. However, it won't have that much impact since $n$'s impact is polynomal.