Skip to main content
If you install and configure HashiCorp Vault without HSM Auto Unseal, Vault employs Shamir’s Secret Sharing Algorithm (en.wikipedia.org/wiki/Shamir%27s_secret_sharing) to prevent one person from having complete access to the system. This process divides a secret into a subset of parts so that you need a subset of those parts to reconstruct the original secret. Vault uses this algorithm as part of the unsealing process (developer.hashicorp.com/vault/docs/concepts/seal). When you initialize a Vault server, Vault generates a root key (previously known as master key) and splits this root key into a series of key shares following Shamir’s Secret Sharing Algorithm. The root key decrypts the underlying encryption key. Vault uses the encryption key to encrypt data at rest in a storage backend such as Integrated Storage (developer.hashicorp.com/vault/tutorials/raft/raft-storage). Distribute each of these key shares to trusted parties in the organization. These parties must then unite to unseal the Vault by entering their key share. In some cases, such as the following ones, you might want to re-generate the root key and its key shares:
  • Someone joins or leaves the organization.
  • Security wants to change the number of shares or the threshold.
  • Compliance mandates that you rotate the keys at regular intervals.
In addition to rekeying the root key, you might need to rotate the underlying encryption key that Vault uses to encrypt data at rest. In Vault, rekeying and rotating are two separate operations.Rekeying is the process of generating a new root key and applying Shamir’s algorithm. Key rotation is the process of generating a new encryption key for Vault. When you deploy Vault with HSM Auto Unseal, the initial Vault server setup involves generating a root key on the KMES Series 3 and a set of recovery keys. With Auto Unseal, you create recovery keys instead of unseal keys.

​
Rekeying Vault

To rekey the Vault with HSM Auto Unseal configured, use the vault operator rekey command with the -target=recovery flag. This command generates a new set of recovery keys. It does not generate a new root key on the KMES Series 3. The process can optionally modify the total number of recovery key shares or the recovery key threshold required. Note that recovery keys cannot decrypt the root key; they are purely for authorization purposes.
1
Run the following command to initialize the rekeying operation, modifying the key shares and key threshold values:
Shell
This command generates a nonce value and starts the rekeying process, as shown in the following example output. All other unseal keys must also provide this nonce value. This nonce value is not a secret, so it is safe to distribute over insecure channels, such as chat or email.
Shell
2
Each key holder runs the following command, specifying their unique recovery key in the last field instead of this example recovery key ( 8iJCZkAqmFcIh7KyTQcyH7p/dPVFOUsEnSq/p5E1g9KX):
Shell
The output should be similar to the following example:
None
3
Repeat the step to complete the rekey operation. When the final unseal key holder enters their key, Vault outputs the new recovery keys.
The output should be similar to the following example:
None

​
Rotating the encryption key

Unlike rekeying the Vault, rotating the Vault encryption key does not require a quorum of recovery keys. Anyone with the proper permissions in Vault can perform the encryption key rotation. You can rotate keys automatically or manually.
With Vault 1.7 and later, Vault automatically rotates the backend encryption key before reaching 2^32 encryption operations, adhering to NIST SP 800-32D guidelines.

​
Adjust the automatic key rotation

Perform the following steps to adjust the automatic key rotation:
1
Run the following command to view the current automatic rotation policy:
Shell
This returns the current status and configuration of automatic encryption key rotation, as shown in the following output example:
None
2
Run the following command to configure a time interval for automatic key rotation:
Shell
The output should be similar to the following output example:
None
3
Run the following command to configure the maximum number of encryption operations per key:
Shell
The output should be similar to the following output example:
None

​
Perform manual key rotation

Perform the following steps to perform manual key rotation:
Shell
The output should resemble the following example, which displays the key version and installation time.:
None
This command adds a new key to the keyring. This new key encrypts all new values written to the storage backend.

​
Continuity of operations

Similar to the process with Shamir’s Secret Sharing, both rekeying and rotating operations with HSM Auto Unseal are fully online operations. Vault continues to service requests uninterrupted during these processes.