Note
The section above is in compliance with ANSSI-PA-079 Recommendation R14, which mandates the use of a cryptographically secure and appropriately seeded pseudorandom generator for key and IV material.
Understanding Key Manager cryptography
Reviewed on 23 May 2025 • Published on 23 May 2025
Cryptographic primitives in Scaleway Key ManagerLink to this anchor
This page provides information on the core cryptographic mechanisms used by Key Manager. It explains how cryptographic keys are generated, managed, and used to encrypt data. Key Manager uses these mechanisms in compliance with the cryptographic guidelines issued by France’s national cybersecurity agency, as outlined in the ANSSI-PA-079 recommendations, to ensure the confidentiality and integrity of customer data.
Random number generationLink to this anchor
Key encryption key (KEK) generation
Scaleway Key Manager uses a Cryptographically Secure Pseudorandom Number Generator (CSPRNG) to generate both keying material for managed keys and cryptographically unique initialization vectors (IVs).
This CSPRNG is based on the ChaCha-based pseudorandom number generator provided by modern Linux kernels. It is seeded with high-entropy, unpredictable sources, such as:
- Timing variations from hardware events
- True Random Number Generators (TRNGs), including the
RDSEEDandRDRANDinstructions available on AMD64 processors
Important
The information above applies only to keys generated by Key Manager. If you import a key using the Bring Your Own Key (BYOK) mechanism, these safeguards are not applied to your key material.
Customer-provided KEKs (BYOK)
Scaleway Key Manager supports Bring Your Own Key (BYOK), allowing customers to import their own key material. In this model, Scaleway does not generate keys on behalf of the customer. Instead, the responsibility for generating strong key material lies with the user.
To protect against direct reuse, imported key material is not used directly. Instead, it is processed using the HKDF algorithm (HMAC-based Key Derivation Function) with SHA-256 as the hash algorithm, incorporating secure random bytes added as a salt value.
Symmetric encryptionLink to this anchor
Scaleway Key Manager uses AES-256-GCM (AES with a 256-bit key in Galois/Counter Mode) with authenticated associated data (AEAD) for encrypting and decrypting user payloads.
To reduce the risk of key overuse, plaintext payloads are limited to a maximum size of 64 KiB. A unique 96-bit initialization vector (IV) is generated using the CSPRNG described in the section above.
Note
The section above is in compliance with ANSSI-PA-079 Recommendations R1, R4, and R12 regarding the choice of secure, authenticated symmetric encryption (R1), key and IV uniqueness (R4), payload size limitations and proper use of AEAD modes (R12). Refer to the ANSSI-PA-079 recommendations documentation for more details.
Important
While Key Manager internally uses AES-256-GCM, this does not restrict users to the same algorithm for their data encryption keys (DEKs).
We recommend using cryptographic libraries like Tink, which handle DEK management with robust and reviewed algorithms.
Scaleway provides Tink integrations for Go and Python, which is the preferred integration method.
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