Understanding Scaleway Key Manager

How to use Key Manager?Link to this anchor

We recommend using the keys you store in Key Manager as key encryption keys (KEK), and use them to encrypt and decrypt your data encryption keys (DEK). We do not recommend storing your data encryption keys in Key Manager.

Why use data encryption keys?Link to this anchor

Unlike key encryption keys (KEK), which cannot be accessed, you can use data encryption keys (DEK) to encrypt your data. You can also use data encryption keys outside of Scaleway Key Manager.

The main benefit of using DEKs is that you do not have to re-encrypt your data at each rotation performed in Key Manager. Only the DEK needs to be re-encrypted with a new KEK.

By rotating solely the KEK, the security of data-at-rest is reinforced without needing heavy encryption operations.

When Key Manager generates data encryption keys, a plaintext version of your key is returned for immediate use, and a ciphertext, which is an encrypted copy of the data encryption key, that you can safely store.

What is the difference between ciphertext and plaintext?Link to this anchor

Ciphertext and plaintext are two fundamental terms in encryption.

Plaintext refers to data in its original, readable form, such as a message, document, or file, that has not been encrypted.

It is the information as it appears before any encryption process or after decryption.

Ciphertext is the result of applying an encryption algorithm to plaintext. It is the scrambled, unreadable version of the data that is secure from unauthorized access.

While plaintext can be understood directly by humans or computers, ciphertext requires a decryption key to convert it back into plaintext. This transformation between plaintext and ciphertext ensures the confidentiality of information during storage or transmission, protecting it from being intercepted or read by unauthorized parties.

Which cryptographic operations does Key Manager support?Link to this anchor

Key Manager supports the three following cryptographic operations:

• Encryption
• Decryption
• Data encryption key generation

Management methods you can use with Key ManagerLink to this anchor

Key Manager allows you to create and manage the complete lifecycle of your keys. Below are all the ways you can use Key Manager to manage your data.

• Create a key: You must specify a key usage, which defines the purpose of the key (encryption, signing, etc.) and which encryption algorithm will be used to derive the key.

Upon key creation, Key Manager automatically creates a first key version.

• Retrieve a key: Retrieving a key only returns the metadata associated with the key, not the key versions.

• List keys: You can retrieve a subset of your keys according to filters such as “name”, “description”, “tags”, etc.

• Update a key: You can update the key’s name, description or tags at any time.

• Enable and disable key protection: Enabling key protection prevents accidental deletion of a key. You must disable key protection before deleting a key to which key protection is applied.

• Rotate a key: Rotating a key creates a new key version and makes all previous versions obsolete.

• Delete a key: Deleting a key also deletes all its versions. All data encrypted using the key, including data encryption keys, will become unusable.

Key usage and algorithmsLink to this anchor

The key usage specifies the encryption algorithm used to create subsequent key versions, and the scope of cryptographic operations supported by the key.

Keys with a key usage set to symmetric_encryption are used to encrypt and decrypt data.

Key Manager only supports the AES-256-GCM encryption scheme.

The following parameters, in compliance with the recommendations of the French Cybersecurity Agency (ANSSI), are used when creating and using a key with the AES-256 GCM encryption scheme.

Key derivation algorithmLink to this anchor

Key Manager uses HMAC-based Extract-and-Expand Key Derivation Function (HKDF) as defined in RFC 5869 with SHA-256 as the hash function.

Key materialLink to this anchor

Key Manager generates a 256-bit key using a cryptographically secure random number generator that draws entropy from the /dev/urandom source. This key is then used in a key derivation algorithm to generate a new key version.

Key version lengthLink to this anchor

The key version has a length of 256 bits, ensuring strong cryptographic security.

Block cipherLink to this anchor

For encryption, Key Manager uses the Galois/Counter Mode (GCM), which is a mode of operation for block ciphers, with a block size of 128 bits. GCM encrypts your plaintext data using AES, and authenticates it using a unique “tag”. This means that if anyone tampers with your data, you will know because the tag will not match anymore.