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For migrating unencrypted data to a new Dgraph cluster with encryption enabled, you need to export the database and import data, preferably using the bulk loader.
Encryption at rest refers to the encryption of data stored physically in any digital form. It ensures that sensitive data on disk isn’t readable by any user or app without a valid key required for decryption. Dgraph provides encryption at rest as an enterprise feature. If encryption is enabled, Dgraph uses Advanced Encryption Standard (AES) algorithm to encrypt the data and secure it. Prior to v20.07.0, the encryption key file must be present on the local file system. Starting with v20.07.0, we have added support for encryption keys sitting on Vault servers. This allows an alternate way to configure the encryption keys needed for encrypting the data at rest.

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Set up encryption

To enable encryption, we need to pass a file that stores the data encryption key with the option --encryption key-file=value. The key size must be 16, 24, or 32 bytes long, and the key size determines the corresponding block size for AES encryption (AES-128, AES-192, and AES-256, respectively). You can use the following command to create the encryption key file (set count to the desired key size): 
tr -dc 'a-zA-Z0-9' < /dev/urandom | dd bs=1 count=32 of=enc_key_file
On a macOS you may have to use LC_CTYPE=C; tr -dc 'a-zA-Z0-9' < /dev/urandom | dd bs=1 count=32 of=enc_key_file. To view the key use cat enc_key_file.
Alternatively, you can use the --vault superflag’s options to enable encryption, as explained below.

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Turn on encryption

Here is an example that starts one Zero server and one Alpha server with the encryption feature turned on: 
dgraph zero --my="localhost:5080" --replicas 1 --raft "idx=1"
dgraph alpha --encryption key-file="./enc_key_file" --my="localhost:7080" --zero="localhost:5080"
If multiple Alpha nodes are part of the cluster, you need to pass the --encryption key-file option to each of the Alphas. Once an Alpha has encryption enabled, the encryption key must be provided in order to start the Alpha server. If the Alpha server restarts, the --encryption key-file option must be set along with the key to restart successfully.

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Storing encryption key secret in HashiCorp Vault

You can save the encryption key secret in HashiCorp Vault K/V Secret instead of as file on Dgraph Alpha. To use HashiCorp Vault, meet the following prerequisites for the Vault Server.
  1. Ensure that the Vault server is accessible from Dgraph Alpha and configured using URL http://fqdn[ip]:port.
  2. Enable AppRole Auth method and enable KV Secrets Engine.
  3. Save the value of the key (16, 24, or 32 bytes long) that Dgraph Alpha uses in a KV Secret path (K/V Version 1 or K/V Version 2). For example, you can upload this below to KV Secrets Engine Version 2 path of secret/data/dgraph/alpha: 
    {
  "options": {
    "cas": 0
  },
  "data": {
    "enc_key": "qIvHQBVUpzsOp74PmMJjHAOfwIA1e6zm%"
  }
}
  4. Create or use a role with an attached policy that grants access to the secret. For example, the following policy would grant access to secret/data/dgraph/alpha: 
    path "secret/data/dgraph/*" {
  capabilities = [ "read", "update" ]
}
  5. Using the role_id generated from the previous step, create a corresponding secret_id, and copy the role_id and secret_id over to local files, like ./dgraph/vault/role_id and ./dgraph/vault/secret_id, that’s used by Dgraph Alpha nodes.
The key format for the enc-field option can be defined using enc-format with the values base64 (default) or raw.

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Example using Dgraph CLI with HashiCorp Vault configuration

The following example shows how to use Dgraph with a Vault server that holds the encryption key: 
## Start Dgraph Zero in different terminal tab or window
dgraph zero --my=localhost:5080 --replicas 1 --raft "idx=1"

## Start Dgraph Alpha in different terminal tab or window
dgraph alpha --my="localhost:7080" --zero="localhost:5080" \
  --vault addr="http://localhost:8200";enc-field="enc_key";enc-format="raw";path="secret/data/dgraph/alpha";role-id-file="./role_id";secret-id-file="./secret_id"
If multiple Dgraph Alpha nodes are part of the cluster, you must pass the --encryption key-file flag or the --vault superflag with appropriate superflag options to each of the Dgraph Alpha nodes. After an Alpha node has encryption enabled, you must provide the encryption key to start the Alpha server. If the Alpha server restarts, the --encryption key-file or the --vault superflag’s options must be set along with the key to restart successfully.

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Turn off encryption

You can use Live Loader or Bulk Loader to decrypt the data while importing.

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Change encryption key

The master encryption key set by the --encryption key-file option (or one used in Vault KV store) doesn’t change automatically. The master encryption key encrypts underlying data keys which are changed on a regular basis automatically (more info about this is covered on the encryption-at-rest blog post). Changing the existing key to a new one is called key rotation. You can rotate the master encryption key by using the badger rotate command on both p and w directories for each Alpha. To maintain availability in HA cluster configurations, you can do this rotate the key one Alpha at a time in a rolling manner. You’ll need both the current key and the new key in two different files. Specify the directory you rotate (“p” or “w”) for the --dir flag, the old key for the --old-key-path flag, and the new key with the --new-key-path flag. 
badger rotate --dir p --old-key-path enc_key_file --new-key-path new_enc_key_file
badger rotate --dir w --old-key-path enc_key_file --new-key-path new_enc_key_file
Then, you can start Alpha with the new_enc_key_file key file to use the new key.