InnoDB uses a two tier encryption key architecture, consisting of a master encryption key and tablespace keys. When a tablespace is encrypted, a tablespace key is encrypted and stored in the tablespace header. When an application or authenticated user wants to access encrypted tablespace data, InnoDB uses a master encryption key to decrypt the tablespace key. The decrypted version of a tablespace key never changes, but the master encryption key can be changed as required. This action is referred to as master key rotation.

The data-at-rest encryption feature relies on a keyring component or plugin for master encryption key management.

All MySQL editions provide a component_keyring_file component, which stores keyring data in a file local to the server host.

MySQL Enterprise Edition offers additional keyring components and plugins:

A secure and robust encryption key management solution is critical for security and for compliance with various security standards. When the data-at-rest encryption feature uses a centralized key management solution, the feature is referred to as “MySQL Enterprise Transparent Data Encryption (TDE)”.

The data-at-rest encryption feature supports the Advanced Encryption Standard (AES) block-based encryption algorithm. It uses Electronic Codebook (ECB) block encryption mode for tablespace key encryption and Cipher Block Chaining (CBC) block encryption mode for data encryption.

For frequently asked questions about the data-at-rest encryption feature, see Section A.17, “MySQL 8.4 FAQ: InnoDB Data-at-Rest Encryption”.

default_table_encryption system variable defines the default encryption setting for schemas and general tablespaces. CREATE TABLESPACE and CREATE SCHEMA operations apply the default_table_encryption setting when an ENCRYPTION clause is not specified explicitly.

ALTER SCHEMA and ALTER TABLESPACE operations do not apply the default_table_encryption setting. An ENCRYPTION clause must be specified explicitly to alter the encryption of an existing schema or general tablespace.

The default_table_encryption variable can be set for an individual client connection or globally using SET syntax. For example, the following statement enables default schema and tablespace encryption globally:

mysql> SET GLOBAL default_table_encryption=ON;

The default encryption setting for a schema can also be defined using the DEFAULT ENCRYPTION clause when creating or altering a schema, as in this example:

mysql> CREATE SCHEMA test DEFAULT ENCRYPTION = 'Y';

If the DEFAULT ENCRYPTION clause is not specified when creating a schema, the default_table_encryption setting is applied. The DEFAULT ENCRYPTION clause must be specified to alter the default encryption of an existing schema. Otherwise, the schema retains its current encryption setting.

By default, a table inherits the encryption setting of the schema or general tablespace it is created in. For example, a table created in an encryption-enabled schema is encrypted by default. This behavior enables a DBA to control table encryption usage by defining and enforcing schema and general tablespace encryption defaults.

Encryption defaults are enforced by enabling the table_encryption_privilege_check system variable. When table_encryption_privilege_check is enabled, a privilege check occurs when creating or altering a schema or general tablespace with an encryption setting that differs from the default_table_encryption setting, or when creating or altering a table with an encryption setting that differs from the default schema encryption. When table_encryption_privilege_check is disabled (the default), the privilege check does not occur and the previously mentioned operations are permitted to proceed with a warning.

The TABLE_ENCRYPTION_ADMIN privilege is required to override default encryption settings when table_encryption_privilege_check is enabled. A DBA can grant this privilege to enable a user to deviate from the default_table_encryption setting when creating or altering a schema or general tablespace, or to deviate from the default schema encryption when creating or altering a table. This privilege does not permit deviating from the encryption of a general tablespace when creating or altering a table. A table must have the same encryption setting as the general tablespace it resides in.

A file-per-table tablespace inherits the default encryption of the schema in which the table is created unless an ENCRYPTION clause is specified explicitly in the CREATE TABLE statement.

mysql> CREATE TABLE t1 (c1 INT) ENCRYPTION = 'Y';

To alter the encryption of an existing file-per-table tablespace, an ENCRYPTION clause must be specified.

mysql> ALTER TABLE t1 ENCRYPTION = 'Y';

table_encryption_privilege_check is enabled, specifying an ENCRYPTION clause with a setting that differs from the default schema encryption requires the TABLE_ENCRYPTION_ADMIN privilege. See Defining an Encryption Default for Schemas and General Tablespaces.

The default_table_encryption variable determines the encryption of a newly created general tablespace unless an ENCRYPTION clause is specified explicitly in the CREATE TABLESPACE statement.

mysql> CREATE TABLESPACE `ts1` ADD DATAFILE 'ts1.ibd' ENCRYPTION = 'Y' Engine=InnoDB;

To alter the encryption of an existing general tablespace, an ENCRYPTION clause must be specified.

mysql> ALTER TABLESPACE ts1 ENCRYPTION = 'Y';

If table_encryption_privilege_check is enabled, specifying an ENCRYPTION clause with a setting that differs from the default_table_encryption setting requires the TABLE_ENCRYPTION_ADMIN privilege. See Defining an Encryption Default for Schemas and General Tablespaces.

In MySQL 8.4, InnoDB automatically encrypts doublewrite file pages that belong to encrypted tablespaces. No action is required. Doublewrite file pages are encrypted using the encryption key of the associated tablespace. The same encrypted page written to a tablespace data file is also written to a doublewrite file. Doublewrite file pages that belong to an unencrypted tablespace remain unencrypted.

During recovery, encrypted doublewrite file pages are unencrypted and checked for corruption.

The mysql system tablespace contains the mysql system database and MySQL data dictionary tables. It is unencrypted by default. To enable encryption for the mysql system tablespace, specify the tablespace name and the ENCRYPTION option in an ALTER TABLESPACE statement.

mysql> ALTER TABLESPACE mysql ENCRYPTION = 'Y';

To disable encryption for the mysql system tablespace, set ENCRYPTION = 'N' using an ALTER TABLESPACE statement.

mysql> ALTER TABLESPACE mysql ENCRYPTION = 'N';

Enabling or disabling encryption for the mysql system tablespace requires the CREATE TABLESPACE privilege on all tables in the instance (CREATE TABLESPACE on *.*).

Redo log data encryption is enabled using the innodb_redo_log_encrypt configuration option. Redo log encryption is disabled by default.

As with tablespace data, redo log data encryption occurs when redo log data is written to disk, and decryption occurs when redo log data is read from disk. Once redo log data is read into memory, it is in unencrypted form. Redo log data is encrypted and decrypted using the tablespace encryption key.

When innodb_redo_log_encrypt is enabled, unencrypted redo log pages that are present on disk remain unencrypted, and new redo log pages are written to disk in encrypted form. Likewise, when innodb_redo_log_encrypt is disabled, encrypted redo log pages that are present on disk remain encrypted, and new redo log pages are written to disk in unencrypted form.

Redo log encryption metadata, including the tablespace encryption key, is stored in the header of the redo log file with the most recent checkpoint LSN. If the redo log file with the encryption metadata is removed, redo log encryption is disabled.

Once redo log encryption is enabled, a normal restart without the keyring component or plugin or without the encryption key is not possible, as InnoDB must be able to scan redo pages during startup, which is not possible if redo log pages are encrypted. Without the keyring component or plugin or the encryption key, only a forced startup without the redo logs (SRV_FORCE_NO_LOG_REDO) is possible. See Section 17.20.3, “Forcing InnoDB Recovery”.

Undo log data encryption is enabled using the innodb_undo_log_encrypt configuration option. Undo log encryption applies to undo logs that reside in undo tablespaces. See Section 17.6.3.4, “Undo Tablespaces”. Undo log data encryption is disabled by default.

As with tablespace data, undo log data encryption occurs when undo log data is written to disk, and decryption occurs when undo log data is read from disk. Once undo log data is read into memory, it is in unencrypted form. Undo log data is encrypted and decrypted using the tablespace encryption key.

When innodb_undo_log_encrypt is enabled, unencrypted undo log pages that are present on disk remain unencrypted, and new undo log pages are written to disk in encrypted form. Likewise, when innodb_undo_log_encrypt is disabled, encrypted undo log pages that are present on disk remain encrypted, and new undo log pages are written to disk in unencrypted form.

Undo log encryption metadata, including the tablespace encryption key, is stored in the header of the undo log file.

The master encryption key should be rotated periodically and whenever you suspect that the key has been compromised.

Master key rotation is an atomic, instance-level operation. Each time the master encryption key is rotated, all tablespace keys in the MySQL instance are re-encrypted and saved back to their respective tablespace headers. As an atomic operation, re-encryption must succeed for all tablespace keys once a rotation operation is initiated. If master key rotation is interrupted by a server failure, InnoDB rolls the operation forward on server restart. For more information, see Encryption and Recovery.

Rotating the master encryption key only changes the master encryption key and re-encrypts tablespace keys. It does not decrypt or re-encrypt associated tablespace data.

Rotating the master encryption key requires the ENCRYPTION_KEY_ADMIN privilege (or the deprecated SUPER privilege).

To rotate the master encryption key, run:

mysql> ALTER INSTANCE ROTATE INNODB MASTER KEY;

ALTER INSTANCE ROTATE INNODB MASTER KEY supports concurrent DML. However, it cannot be run concurrently with tablespace encryption operations, and locks are taken to prevent conflicts that could arise from concurrent execution. If an ALTER INSTANCE ROTATE INNODB MASTER KEY operation is running, it must finish before a tablespace encryption operation can proceed, and vice versa.

If a server failure occurs during an encryption operation, the operation is rolled forward when the server is restarted. For general tablespaces, the encryption operation is resumed in a background thread from the last processed page.

If a server failure occurs during master key rotation, InnoDB continues the operation on server restart.

The keyring component or plugin must be loaded prior to storage engine initialization so that the information necessary to decrypt tablespace data pages can be retrieved from tablespace headers before InnoDB initialization and recovery activities access tablespace data. (See Encryption Prerequisites.)

When InnoDB initialization and recovery begin, the master key rotation operation resumes. Due to the server failure, some tablespace keys may already be encrypted using the new master encryption key. InnoDB reads the encryption data from each tablespace header, and if the data indicates that the tablespace key is encrypted using the old master encryption key, InnoDB retrieves the old key from the keyring and uses it to decrypt the tablespace key. InnoDB then re-encrypts the tablespace key using the new master encryption key and saves the re-encrypted tablespace key back to the tablespace header.

Tablespace export is only supported for file-per-table tablespaces.

When an encrypted tablespace is exported, InnoDB generates a transfer key that is used to encrypt the tablespace key. The encrypted tablespace key and transfer key are stored in a tablespace_name.cfp file. This file together with the encrypted tablespace file is required to perform an import operation. On import, InnoDB uses the transfer key to decrypt the tablespace key in the tablespace_name.cfp file. For related information, see Section 17.6.1.3, “Importing InnoDB Tables”.

The Information Schema INNODB_TABLESPACES table includes an ENCRYPTION column that can be used to identify encrypted tablespaces.

mysql> SELECT SPACE, NAME, SPACE_TYPE, ENCRYPTION FROM INFORMATION_SCHEMA.INNODB_TABLESPACES
       WHERE ENCRYPTION='Y'\G
*************************** 1. row ***************************
     SPACE: 4294967294
      NAME: mysql
SPACE_TYPE: General
ENCRYPTION: Y
*************************** 2. row ***************************
     SPACE: 2
      NAME: test/t1
SPACE_TYPE: Single
ENCRYPTION: Y
*************************** 3. row ***************************
     SPACE: 3
      NAME: ts1
SPACE_TYPE: General
ENCRYPTION: Y

When the ENCRYPTION option is specified in a CREATE TABLE or ALTER TABLE statement, it is recorded in the CREATE_OPTIONS column of INFORMATION_SCHEMA.TABLES. This column can be queried to identify tables that reside in encrypted file-per-table tablespaces.

mysql> SELECT TABLE_SCHEMA, TABLE_NAME, CREATE_OPTIONS FROM INFORMATION_SCHEMA.TABLES
       WHERE CREATE_OPTIONS LIKE '%ENCRYPTION%';
+--------------+------------+----------------+
| TABLE_SCHEMA | TABLE_NAME | CREATE_OPTIONS |
+--------------+------------+----------------+
| test         | t1         | ENCRYPTION="Y" |
+--------------+------------+----------------+

Query the Information Schema INNODB_TABLESPACES table to retrieve information about the tablespace associated with a particular schema and table.

mysql> SELECT SPACE, NAME, SPACE_TYPE FROM INFORMATION_SCHEMA.INNODB_TABLESPACES WHERE NAME='test/t1';
+-------+---------+------------+
| SPACE | NAME    | SPACE_TYPE |
+-------+---------+------------+
|     3 | test/t1 | Single     |
+-------+---------+------------+

You can identify encryption-enabled schemas by querying the Information Schema SCHEMATA table.

mysql> SELECT SCHEMA_NAME, DEFAULT_ENCRYPTION FROM INFORMATION_SCHEMA.SCHEMATA
       WHERE DEFAULT_ENCRYPTION='YES';
+-------------+--------------------+
| SCHEMA_NAME | DEFAULT_ENCRYPTION |
+-------------+--------------------+
| test        | YES                |
+-------------+--------------------+

SHOW CREATE SCHEMA also shows the DEFAULT ENCRYPTION clause.

You can monitor general tablespace and mysql system tablespace encryption progress using Performance Schema.

The stage/innodb/alter tablespace (encryption) stage event instrument reports WORK_ESTIMATED and WORK_COMPLETED information for general tablespace encryption operations.

The following example demonstrates how to enable the stage/innodb/alter tablespace (encryption) stage event instrument and related consumer tables to monitor general tablespace or mysql system tablespace encryption progress. For information about Performance Schema stage event instruments and related consumers, see Section 29.12.5, “Performance Schema Stage Event Tables”.