> ## Documentation Index > Fetch the complete documentation index at: https://private-7c7dfe99-mintlify-1d264819.mintlify.site/llms.txt > Use this file to discover all available pages before exploring further. > Documentation for encryption functions # Encryption functions These functions implement encryption and decryption of data with AES (Advanced Encryption Standard) algorithm. The key length depends on the encryption mode: `16`, `24`, and `32` bytes long for `-128-`, `-196-`, and `-256-` modes respectively. The initialization vector length is always 16 bytes (bytes in excess of 16 are ignored). {/*AUTOGENERATED_START*/}

HMAC

Introduced in: v25.12.0 Computes the HMAC (Hash-based Message Authentication Code) for the given message using the specified hash algorithm and secret key. Supported hash algorithms: * blake2b512 * blake2s256 * md4 * md5 * md5-sha1 * mdc2 * ripemd (aliases: RIPEMD160, ripemd) * ripemd160 * rmd160 (aliases: RIPEMD160, rmd160) * sha1 * sha224 * sha256 * sha3-224 * sha3-256 * sha3-384 * sha3-512 * sha384 * sha512 * sha512-224 * sha512-256 * shake128 * shake256 * sm3 * ssl3-md5 (aliases: MD5, ssl3-md5) * ssl3-sha1 (aliases: SHA1, ssl3-sha1) * whirlpool **Syntax** ```sql theme={null} HMAC(mode, message, key) ``` **Arguments** * `mode` — Hash algorithm name (case-insensitive). Supported: md5, sha1, sha224, sha256, sha384, sha512. [`String`](/reference/data-types/string) * `message` — Message to be authenticated. [`String`](/reference/data-types/string) * `key` — Secret key for HMAC. [`String`](/reference/data-types/string) **Returned value** Returns a binary string containing the HMAC digest. [`String`](/reference/data-types/string) **Examples** **Basic HMAC-SHA256** ```sql title=Query theme={null} SELECT hex(HMAC('sha256', 'The quick brown fox jumps over the lazy dog', 'secret_key')); ``` ```response title=Response theme={null} ┌─hex(HMAC('sha256', 'The quick brown fox jumps over the lazy dog', 'secret_key'))─┐ │ 31FD15FA0F61FD40DC09D919D4AA5B4141A0B27C1D51E74A6789A890AAAA187C │ └──────────────────────────────────────────────────────────────────────────────────┘ ``` **Different hash algorithms** ```sql title=Query theme={null} SELECT hex(HMAC('md5', 'message', 'key')) AS hmac_md5, hex(HMAC('sha1', 'message', 'key')) AS hmac_sha1, hex(HMAC('sha256', 'message', 'key')) AS hmac_sha256; ``` ```response title=Response theme={null} ┌─hmac_md5─────────────────────────┬─hmac_sha1────────────────────────────────┬─hmac_sha256──────────────────────────────────────────────────────┐ │ 4E4748E62B463521F6775FBF921234B5 │ 2088DF74D5F2146B48146CAF4965377E9D0BE3A4 │ 6E9EF29B75FFFC5B7ABAE527D58FDADB2FE42E7219011976917343065F58ED4A │ └──────────────────────────────────┴──────────────────────────────────────────┴──────────────────────────────────────────────────────────────────┘ ``` **Case-insensitive mode** ```sql title=Query theme={null} SELECT hmac('SHA256', 'message', 'key') = HMAC('sha256', 'message', 'key') AS same_result, HMAC('SHA256', 'message', 'key') = Hmac('Sha256', 'message', 'key') AS also_same; ``` ```response title=Response theme={null} ┌─same_result─┬─also_same─┐ │ 1 │ 1 │ └─────────────┴───────────┘ ```

aes\_decrypt\_mysql

Introduced in: v20.12.0 Decrypts data encrypted by MySQL's [`AES_ENCRYPT`](https://dev.mysql.com/doc/refman/8.0/en/encryption-functions.html#function_aes-encrypt) function. Produces the same plaintext as [`decrypt`](#decrypt) for the same inputs. When `key` or `iv` are longer than they should normally be, `aes_decrypt_mysql` will stick to what MySQL's `aes_decrypt` does which is to 'fold' `key` and ignore the excess bits of `IV`. Supports the following decryption modes: * aes-128-ecb, aes-192-ecb, aes-256-ecb * aes-128-cbc, aes-192-cbc, aes-256-cbc * aes-128-cfb128 * aes-128-ofb, aes-192-ofb, aes-256-ofb **Syntax** ```sql theme={null} aes_decrypt_mysql(mode, ciphertext, key[, iv]) ``` **Arguments** * `mode` — Decryption mode. [`String`](/reference/data-types/string) * `ciphertext` — Encrypted text that needs to be decrypted. [`String`](/reference/data-types/string) * `key` — Decryption key. [`String`](/reference/data-types/string) * `iv` — Optional. Initialization vector. [`String`](/reference/data-types/string) **Returned value** Returns the decrypted String. [`String`](/reference/data-types/string) **Examples** **Decrypt MySQL data** ```sql title=Query theme={null} -- Let's decrypt data we've previously encrypted with MySQL: mysql> SET block_encryption_mode='aes-256-ofb'; Query OK, 0 rows affected (0.00 sec) mysql> SELECT aes_encrypt('Secret', '123456789101213141516171819202122', 'iviviviviviviviv123456') as ciphertext; +------------------------+ | ciphertext | +------------------------+ | 0x24E9E4966469 | +------------------------+ 1 row in set (0.00 sec) SELECT aes_decrypt_mysql('aes-256-ofb', unhex('24E9E4966469'), '123456789101213141516171819202122', 'iviviviviviviviv123456') AS plaintext ``` ```response title=Response theme={null} ┌─plaintext─┐ │ Secret │ └───────────┘ ```

aes\_encrypt\_mysql

Introduced in: v20.12.0 Encrypts text the same way as MySQL's `AES_ENCRYPT` function does. The resulting ciphertext can be decrypted with MySQL's `AES_DECRYPT` function. Produces the same ciphertext as the `encrypt` function for the same inputs. When `key` or `iv` are longer than they should normally be, `aes_encrypt_mysql` will stick to what MySQL's `aes_encrypt` does which is to 'fold' `key` and ignore the excess bits of `iv`. The supported encryption modes are: * aes-128-ecb, aes-192-ecb, aes-256-ecb * aes-128-cbc, aes-192-cbc, aes-256-cbc * aes-128-ofb, aes-192-ofb, aes-256-ofb **Syntax** ```sql theme={null} aes_encrypt_mysql(mode, plaintext, key[, iv]) ``` **Arguments** * `mode` — Encryption mode. [`String`](/reference/data-types/string) * `plaintext` — Text that should be encrypted. [`String`](/reference/data-types/string) * `key` — Encryption key. If the key is longer than required by `mode`, MySQL-specific key folding is performed. [`String`](/reference/data-types/string) * `iv` — Optional. Initialization vector. Only the first 16 bytes are taken into account. [`String`](/reference/data-types/string) **Returned value** Ciphertext binary string. [`String`](/reference/data-types/string) **Examples** **Equal input comparison** ```sql title=Query theme={null} -- Given equal input encrypt and aes_encrypt_mysql produce the same ciphertext: SELECT encrypt('aes-256-ofb', 'Secret', '12345678910121314151617181920212', 'iviviviviviviviv') = aes_encrypt_mysql('aes-256-ofb', 'Secret', '12345678910121314151617181920212', 'iviviviviviviviv') AS ciphertexts_equal; ``` ```response title=Response theme={null} ┌─ciphertexts_equal─┐ │ 1 │ └───────────────────┘ ``` **Encrypt fails with long key** ```sql title=Query theme={null} -- But encrypt fails when key or iv is longer than expected: SELECT encrypt('aes-256-ofb', 'Secret', '123456789101213141516171819202122', 'iviviviviviviviv123'); ``` ```response title=Response theme={null} Received exception from server (version 22.6.1): Code: 36. DB::Exception: Received from localhost:9000. DB::Exception: Invalid key size: 33 expected 32: While processing encrypt('aes-256-ofb', 'Secret', '123456789101213141516171819202122', 'iviviviviviviviv123'). ``` **MySQL compatibility** ```sql title=Query theme={null} -- aes_encrypt_mysql produces MySQL-compatible output: SELECT hex(aes_encrypt_mysql('aes-256-ofb', 'Secret', '123456789101213141516171819202122', 'iviviviviviviviv123')) AS ciphertext; ``` ```response title=Response theme={null} ┌─ciphertext───┐ │ 24E9E4966469 │ └──────────────┘ ``` **Longer IV produces the same result** ```sql title=Query theme={null} -- Notice how supplying even longer IV produces the same result SELECT hex(aes_encrypt_mysql('aes-256-ofb', 'Secret', '123456789101213141516171819202122', 'iviviviviviviviv123456')) AS ciphertext ``` ```response title=Response theme={null} ┌─ciphertext───┐ │ 24E9E4966469 │ └──────────────┘ ```

decrypt

Introduced in: v20.12.0 This function decrypts an AES-encrypted binary string using the following modes: * aes-128-ecb, aes-192-ecb, aes-256-ecb * aes-128-cbc, aes-192-cbc, aes-256-cbc * aes-128-ofb, aes-192-ofb, aes-256-ofb * aes-128-gcm, aes-192-gcm, aes-256-gcm * aes-128-ctr, aes-192-ctr, aes-256-ctr * aes-128-cfb, aes-128-cfb1, aes-128-cfb8 **Syntax** ```sql theme={null} decrypt(mode, ciphertext, key[, iv, aad]) ``` **Arguments** * `mode` — Decryption mode. [`String`](/reference/data-types/string) * `ciphertext` — Encrypted text that should be decrypted. [`String`](/reference/data-types/string) * `key` — Decryption key. [`String`](/reference/data-types/string) * `iv` — Initialization vector. Required for `-gcm` modes, optional for others. [`String`](/reference/data-types/string) * `aad` — Additional authenticated data. Won't decrypt if this value is incorrect. Works only in `-gcm` modes, for others throws an exception. [`String`](/reference/data-types/string) **Returned value** Returns decrypted plaintext. [`String`](/reference/data-types/string) **Examples** **Correctly decrypting encrypted data** ```sql title=Query theme={null} -- Re-using the table from the encrypt function example SELECT comment, hex(secret) FROM encryption_test; ``` ```response title=Response theme={null} ┌─comment──────────────┬─hex(secret)──────────────────────────────────┐ │ aes-256-gcm │ A8A3CCBC6426CFEEB60E4EAE03D3E94204C1B09E0254 │ │ aes-256-gcm with AAD │ A8A3CCBC6426D9A1017A0A932322F1852260A4AD6837 │ └──────────────────────┴──────────────────────────────────────────────┘ ┌─comment──────────────────────────┬─hex(secret)──────────────────────┐ │ aes-256-ofb no IV │ B4972BDC4459 │ │ aes-256-ofb no IV, different key │ 2FF57C092DC9 │ │ aes-256-ofb with IV │ 5E6CB398F653 │ │ aes-256-cbc no IV │ 1BC0629A92450D9E73A00E7D02CF4142 │ └──────────────────────────────────┴──────────────────────────────────┘ ``` **Incorrectly decrypting encrypted data** ```sql title=Query theme={null} SELECT comment, decrypt('aes-256-cfb128', secret, '12345678910121314151617181920212') AS plaintext FROM encryption_test ``` ```response title=Response theme={null} -- Notice how only a portion of the data was properly decrypted, and the rest is gibberish since either `mode`, `key`, or `iv` were different upon encryption. ┌─comment──────────────┬─plaintext──┐ │ aes-256-gcm │ OQ�E �t�7T�\���\� │ │ aes-256-gcm with AAD │ OQ�E �\��si����;�o�� │ └──────────────────────┴────────────┘ ┌─comment──────────────────────────┬─plaintext─┐ │ aes-256-ofb no IV │ Secret │ │ aes-256-ofb no IV, different key │ �4� � │ │ aes-256-ofb with IV │ ���6�~ │ │aes-256-cbc no IV │ �2*4�h3c�4w��@ └──────────────────────────────────┴───────────┘ ```

encrypt

Introduced in: v20.12.0 Encrypts plaintext into ciphertext using AES in one of the following modes: * aes-128-ecb, aes-192-ecb, aes-256-ecb * aes-128-cbc, aes-192-cbc, aes-256-cbc * aes-128-ofb, aes-192-ofb, aes-256-ofb * aes-128-gcm, aes-192-gcm, aes-256-gcm * aes-128-ctr, aes-192-ctr, aes-256-ctr * aes-128-cfb, aes-128-cfb1, aes-128-cfb8 **Syntax** ```sql theme={null} encrypt(mode, plaintext, key[, iv, aad]) ``` **Arguments** * `mode` — Encryption mode. [`String`](/reference/data-types/string) * `plaintext` — Text that should be encrypted. [`String`](/reference/data-types/string) * `key` — Encryption key. [`String`](/reference/data-types/string) * `iv` — Initialization vector. Required for `-gcm` modes, optional for others. [`String`](/reference/data-types/string) * `aad` — Additional authenticated data. It isn't encrypted, but it affects decryption. Works only in `-gcm` modes, for others it throws an exception. [`String`](/reference/data-types/string) **Returned value** Returns binary string ciphertext. [`String`](/reference/data-types/string) **Examples** **Example encryption** ```sql title=Query theme={null} CREATE TABLE encryption_test ( `comment` String, `secret` String ) ENGINE = MergeTree; INSERT INTO encryption_test VALUES ('aes-256-ofb no IV', encrypt('aes-256-ofb', 'Secret', '12345678910121314151617181920212')), ('aes-256-ofb no IV, different key', encrypt('aes-256-ofb', 'Secret', 'keykeykeykeykeykeykeykeykeykeyke')), ('aes-256-ofb with IV', encrypt('aes-256-ofb', 'Secret', '12345678910121314151617181920212', 'iviviviviviviviv')), ('aes-256-cbc no IV', encrypt('aes-256-cbc', 'Secret', '12345678910121314151617181920212')); SELECT comment, hex(secret) FROM encryption_test; ``` ```response title=Response theme={null} ┌─comment──────────────────────────┬─hex(secret)──────────────────────┐ │ aes-256-ofb no IV │ B4972BDC4459 │ │ aes-256-ofb no IV, different key │ 2FF57C092DC9 │ │ aes-256-ofb with IV │ 5E6CB398F653 │ │ aes-256-cbc no IV │ 1BC0629A92450D9E73A00E7D02CF4142 │ └──────────────────────────────────┴──────────────────────────────────┘ ``` **Example with GCM mode** ```sql title=Query theme={null} INSERT INTO encryption_test VALUES ('aes-256-gcm', encrypt('aes-256-gcm', 'Secret', '12345678910121314151617181920212', 'iviviviviviviviv')), ('aes-256-gcm with AAD', encrypt('aes-256-gcm', 'Secret', '12345678910121314151617181920212', 'iviviviviviviviv', 'aad')); SELECT comment, hex(secret) FROM encryption_test WHERE comment LIKE '%gcm%'; ``` ```response title=Response theme={null} ┌─comment──────────────┬─hex(secret)──────────────────────────────────┐ │ aes-256-gcm │ A8A3CCBC6426CFEEB60E4EAE03D3E94204C1B09E0254 │ │ aes-256-gcm with AAD │ A8A3CCBC6426D9A1017A0A932322F1852260A4AD6837 │ └──────────────────────┴──────────────────────────────────────────────┘ ```

tryDecrypt

Introduced in: v22.10.0 Similar to the `decrypt` function, but returns `NULL` if decryption fails when using the wrong key. **Syntax** ```sql theme={null} tryDecrypt(mode, ciphertext, key[, iv, aad]) ``` **Arguments** * `mode` — Decryption mode. [`String`](/reference/data-types/string) * `ciphertext` — Encrypted text that should be decrypted. [`String`](/reference/data-types/string) * `key` — Decryption key. [`String`](/reference/data-types/string) * `iv` — Optional. Initialization vector. Required for `-gcm` modes, optional for other modes. [`String`](/reference/data-types/string) * `aad` — Optional. Additional authenticated data. Won't decrypt if this value is incorrect. Works only in `-gcm` modes, for other modes throws an exception. [`String`](/reference/data-types/string) **Returned value** Returns the decrypted String, or `NULL` if decryption fails. [`Nullable(String)`](/reference/data-types/nullable) **Examples** **Create table and insert data** ```sql title=Query theme={null} -- Let's create a table where user_id is the unique user id, encrypted is an encrypted string field, iv is an initial vector for decrypt/encrypt. -- Assume that users know their id and the key to decrypt the encrypted field: CREATE TABLE decrypt_null ( dt DateTime, user_id UInt32, encrypted String, iv String ) ENGINE = MergeTree; -- Insert some data: INSERT INTO decrypt_null VALUES ('2022-08-02 00:00:00', 1, encrypt('aes-256-gcm', 'value1', 'keykeykeykeykeykeykeykeykeykey01', 'iv1'), 'iv1'), ('2022-09-02 00:00:00', 2, encrypt('aes-256-gcm', 'value2', 'keykeykeykeykeykeykeykeykeykey02', 'iv2'), 'iv2'), ('2022-09-02 00:00:01', 3, encrypt('aes-256-gcm', 'value3', 'keykeykeykeykeykeykeykeykeykey03', 'iv3'), 'iv3'); -- Try decrypt with one key SELECT dt, user_id, tryDecrypt('aes-256-gcm', encrypted, 'keykeykeykeykeykeykeykeykeykey02', iv) AS value FROM decrypt_null ORDER BY user_id ASC ``` ```response title=Response theme={null} ┌──────────────────dt─┬─user_id─┬─value──┐ │ 2022-08-02 00:00:00 │ 1 │ ᴺᵁᴸᴸ │ │ 2022-09-02 00:00:00 │ 2 │ value2 │ │ 2022-09-02 00:00:01 │ 3 │ ᴺᵁᴸᴸ │ └─────────────────────┴─────────┴────────┘ ```