Post-Quantum Encryption

QuantaBox's defining feature is post-quantum disk encryption. This chapter explains what it protects, how to use it, and what happens to your keys. For the cryptographic design, see Cryptography Internals.

What It Protects #

Disk encryption protects your VM's data at rest: the contents of the disk image file on your host. If someone copies your .qvd/.qcow2 file, or steals the drive it lives on, they cannot read the guest's data without the key.

It does not protect a running VM's live memory, nor does it replace good host security. It is one layer of defense, focused on data on disk.

Why "Post-Quantum"? #

Encryption has two parts: a fast symmetric cipher that encrypts the data, and a mechanism that protects the cipher's key. QuantaBox uses:

• AES-256-GCM to encrypt disk contents. At 256-bit keys, AES is considered resistant to known quantum attacks.
• ML-KEM-768 (NIST FIPS 203) to wrap (protect) the disk's encryption key. ML-KEM is a post-quantum key-encapsulation mechanism designed to resist attacks by future quantum computers.

The combination is reported by QuantaBox as ML-KEM-768 + AES-256-GCM. This defeats "harvest now, decrypt later" attacks, where an adversary stores your encrypted disks today hoping to break the key with a quantum computer in the future.

Enabling Encryption #

The simplest path is at VM creation:

1. In the Create Virtual Machine dialog, leave PQC Disk Encryption ticked (it is on by default).
2. Create the VM. Its primary disk is created as an encrypted QVD image.

CLI:

quantabox create secure-vm --os ubuntu-2404-desktop --encrypted

You can confirm a VM's encryption status in the Details tab or with quantabox info <vm>.

How Keys Are Protected #

Understanding the key hierarchy helps you keep your data recoverable:

                     +-----------------------------+
Disk contents  <---->|  AES-256-GCM (per-disk DEK)  |   encrypts every sector
                     +-------------+---------------+
                                   | the DEK is wrapped by...
                     +-------------v---------------+
                     |  ML-KEM-768 key encapsulation|   quantum-resistant wrapping
                     +-------------+---------------+
                                   | wrapped DEK stored in...
                     +-------------v---------------+
                     |  Key Vault (master-key       |   on your host
                     |  protected JSON store)       |
                     +-----------------------------+

• Each encrypted disk has its own Disk Encryption Key (DEK), a 256-bit AES key.
• The DEK is wrapped (encrypted) using ML-KEM-768, so the stored key material is quantum-resistant.
• Wrapped keys live in QuantaBox's key vault, itself protected by a master key on your host.

Sectors are encrypted independently with counter-derived nonces, which is what allows fast random-access reads and writes on an encrypted disk.

Keys and Recoverability #

• If you lose the key vault or master key, encrypted disks are unrecoverable. There is no backdoor. That is the point of strong encryption.
• Back up your key vault together with your VMs. An encrypted export keeps key material with the package so it can be restored elsewhere.
• Treat the master key like the most sensitive secret on your machine.

Encrypted Export and Backup #

When you export or back up a VM, you can carry the encryption through to the package so it stays protected in transit and at the destination:

quantabox package export secure-vm secure-vm.tar --encrypted

See Backup, Export and Import for the full workflow.

Next #

Continue to The ISO Library to get operating systems for your VMs.