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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).

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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 
HMAC(mode, message, key)
Arguments
  • mode — Hash algorithm name (case-insensitive). Supported: md5, sha1, sha224, sha256, sha384, sha512. String
  • message — Message to be authenticated. String
  • key — Secret key for HMAC. String
Returned value Returns a binary string containing the HMAC digest. String Examples Basic HMAC-SHA256
Query
SELECT hex(HMAC('sha256', 'The quick brown fox jumps over the lazy dog', 'secret_key'));
Response
┌─hex(HMAC('sha256', 'The quick brown fox jumps over the lazy dog', 'secret_key'))─┐
│ 31FD15FA0F61FD40DC09D919D4AA5B4141A0B27C1D51E74A6789A890AAAA187C                 │
└──────────────────────────────────────────────────────────────────────────────────┘
Different hash algorithms
Query
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
┌─hmac_md5─────────────────────────┬─hmac_sha1────────────────────────────────┬─hmac_sha256──────────────────────────────────────────────────────┐
│ 4E4748E62B463521F6775FBF921234B5 │ 2088DF74D5F2146B48146CAF4965377E9D0BE3A4 │ 6E9EF29B75FFFC5B7ABAE527D58FDADB2FE42E7219011976917343065F58ED4A │
└──────────────────────────────────┴──────────────────────────────────────────┴──────────────────────────────────────────────────────────────────┘
Case-insensitive mode
Query
SELECT
    hmac('SHA256', 'message', 'key') = HMAC('sha256', 'message', 'key') AS same_result,
    HMAC('SHA256', 'message', 'key') = Hmac('Sha256', 'message', 'key') AS also_same;
Response
┌─same_result─┬─also_same─┐
│           1 │         1 │
└─────────────┴───────────┘

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aes_decrypt_mysql

Introduced in: v20.12.0 Decrypts data encrypted by MySQL’s AES_ENCRYPT function. Produces the same plaintext as 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 
aes_decrypt_mysql(mode, ciphertext, key[, iv])
Arguments
  • mode — Decryption mode. String
  • ciphertext — Encrypted text that needs to be decrypted. String
  • key — Decryption key. String
  • iv — Optional. Initialization vector. String
Returned value Returns the decrypted String. String Examples Decrypt MySQL data
Query
-- 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
┌─plaintext─┐
│ Secret    │
└───────────┘

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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 
aes_encrypt_mysql(mode, plaintext, key[, iv])
Arguments
  • mode — Encryption mode. String
  • plaintext — Text that should be encrypted. String
  • key — Encryption key. If the key is longer than required by mode, MySQL-specific key folding is performed. String
  • iv — Optional. Initialization vector. Only the first 16 bytes are taken into account. String
Returned value Ciphertext binary string. String Examples Equal input comparison
Query
-- 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
┌─ciphertexts_equal─┐
│                 1 │
└───────────────────┘
Encrypt fails with long key
Query
-- But encrypt fails when key or iv is longer than expected:
SELECT encrypt('aes-256-ofb', 'Secret', '123456789101213141516171819202122', 'iviviviviviviviv123');
Response
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
Query
-- aes_encrypt_mysql produces MySQL-compatible output:
SELECT hex(aes_encrypt_mysql('aes-256-ofb', 'Secret', '123456789101213141516171819202122', 'iviviviviviviviv123')) AS ciphertext;
Response
┌─ciphertext───┐
│ 24E9E4966469 │
└──────────────┘
Longer IV produces the same result
Query
-- Notice how supplying even longer IV produces the same result
SELECT hex(aes_encrypt_mysql('aes-256-ofb', 'Secret', '123456789101213141516171819202122', 'iviviviviviviviv123456')) AS ciphertext
Response
┌─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 
decrypt(mode, ciphertext, key[, iv, aad])
Arguments
  • mode — Decryption mode. String
  • ciphertext — Encrypted text that should be decrypted. String
  • key — Decryption key. String
  • iv — Initialization vector. Required for -gcm modes, optional for others. String
  • aad — Additional authenticated data. Won’t decrypt if this value is incorrect. Works only in -gcm modes, for others throws an exception. String
Returned value Returns decrypted plaintext. String Examples Correctly decrypting encrypted data
Query
-- Re-using the table from the encrypt function example
SELECT comment, hex(secret) FROM encryption_test;
Response
┌─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
Query
SELECT comment, decrypt('aes-256-cfb128', secret, '12345678910121314151617181920212') AS plaintext FROM encryption_test
Response
-- 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 
encrypt(mode, plaintext, key[, iv, aad])
Arguments
  • mode — Encryption mode. String
  • plaintext — Text that should be encrypted. String
  • key — Encryption key. String
  • iv — Initialization vector. Required for -gcm modes, optional for others. 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
Returned value Returns binary string ciphertext. String Examples Example encryption
Query
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
┌─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
Query
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
┌─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 
tryDecrypt(mode, ciphertext, key[, iv, aad])
Arguments
  • mode — Decryption mode. String
  • ciphertext — Encrypted text that should be decrypted. String
  • key — Decryption key. String
  • iv — Optional. Initialization vector. Required for -gcm modes, optional for other modes. 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
Returned value Returns the decrypted String, or NULL if decryption fails. Nullable(String) Examples Create table and insert data
Query
-- 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
┌──────────────────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   │
└─────────────────────┴─────────┴────────┘