Relational Data - Functions - Encryption Functions

These functions implement encryption and decryption of data with AES (Advanced Encryption Standard) algorithm.

Key length depends on encryption mode. It is 16, 24, and 32 bytes long for -128-, -196-, and -256- modes respectively.

Initialization vector length is always 16 bytes (bytes in excess of 16 are ignored).

Note that these functions work slowly until ClickHouse 21.1.

encrypt

This function encrypts data using these 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

Syntax

encrypt('mode', 'plaintext', 'key' [, iv, aad])

Arguments

• mode — Encryption mode. String.
• plaintext — Text that need to 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 would throw an exception. String.

Returned value

• Ciphertext binary string. String.

Examples

Create this table:

Query:

CREATE TABLE encryption_test
(
    `comment` String,
    `secret` String
)
ENGINE = Memory;

Insert some data (please avoid storing the keys/ivs in the database as this undermines the whole concept of encryption), also storing ‘hints’ is unsafe too and used only for illustrative purposes:

Query:

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'));

Query:

SELECT comment, hex(secret) FROM encryption_test;

Result:

┌─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:

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%';

Result:

┌─comment──────────────┬─hex(secret)──────────────────────────────────┐
│ aes-256-gcm          │ A8A3CCBC6426CFEEB60E4EAE03D3E94204C1B09E0254 │
│ aes-256-gcm with AAD │ A8A3CCBC6426D9A1017A0A932322F1852260A4AD6837 │
└──────────────────────┴──────────────────────────────────────────────┘

aes_encrypt_mysql

Compatible with mysql encryption and resulting ciphertext can be decrypted with AES_DECRYPT function.

Will produce the same ciphertext as encrypt on equal inputs. But when key or iv are longer than they should normally be, aes_encrypt_mysql will stick to what MySQL’s aes_encrypt does: ‘fold’ key and ignore excess bits of iv.

Supported encryption 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

Syntax

aes_encrypt_mysql('mode', 'plaintext', 'key' [, iv])

Arguments

• mode — Encryption mode. String.
• plaintext — Text that needs to be encrypted. String.
• key — Encryption key. If key is longer than required by mode, MySQL-specific key folding is performed. String.
• iv — Initialization vector. Optional, only first 16 bytes are taken into account String.

Returned value

• Ciphertext binary string. String.

Examples

Given equal input encrypt and aes_encrypt_mysql produce the same ciphertext:

Query:

SELECT encrypt('aes-256-ofb', 'Secret', '12345678910121314151617181920212', 'iviviviviviviviv') = aes_encrypt_mysql('aes-256-ofb', 'Secret', '12345678910121314151617181920212', 'iviviviviviviviv') AS ciphertexts_equal;

Result:

┌─ciphertexts_equal─┐
│                 1 │
└───────────────────┘

But encrypt fails when key or iv is longer than expected:

Query:

SELECT encrypt('aes-256-ofb', 'Secret', '123456789101213141516171819202122', 'iviviviviviviviv123');

Result:

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').

While aes_encrypt_mysql produces MySQL-compatible output:

Query:

SELECT hex(aes_encrypt_mysql('aes-256-ofb', 'Secret', '123456789101213141516171819202122', 'iviviviviviviviv123')) AS ciphertext;

Result:

┌─ciphertext───┐
│ 24E9E4966469 │
└──────────────┘

Notice how supplying even longer IV produces the same result

Query:

SELECT hex(aes_encrypt_mysql('aes-256-ofb', 'Secret', '123456789101213141516171819202122', 'iviviviviviviviv123456')) AS ciphertext

Result:

┌─ciphertext───┐
│ 24E9E4966469 │
└──────────────┘

Which is binary equal to what MySQL produces on same inputs:

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)

decrypt

This function decrypts ciphertext into a plaintext using these 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

Syntax

decrypt('mode', 'ciphertext', 'key' [, iv, aad])

Arguments

• mode — Decryption mode. String.
• ciphertext — Encrypted text that needs to 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 would throw an exception. String.

Returned value

• Decrypted String. String.

Examples

Re-using table from encrypt.

Query:

SELECT comment, hex(secret) FROM encryption_test;

Result:

┌─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 │
└──────────────────────────────────┴──────────────────────────────────┘

Now let’s try to decrypt all that data.

Query:

SELECT comment, decrypt('aes-256-cfb128', secret, '12345678910121314151617181920212') as plaintext FROM encryption_test

Result:

┌─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��@
└──────────────────────────────────┴───────────┘

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.

tryDecrypt

Similar to decrypt, but returns NULL if decryption fails because of using the wrong key.

Examples

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 = Memory;

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');

Query:

SELECT
    dt,
    user_id,
    tryDecrypt('aes-256-gcm', encrypted, 'keykeykeykeykeykeykeykeykeykey02', iv) AS value
FROM decrypt_null
ORDER BY user_id ASC

Result:

┌──────────────────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   │
└─────────────────────┴─────────┴────────┘

aes_decrypt_mysql

Compatible with mysql encryption and decrypts data encrypted with AES_ENCRYPT function.

Will produce same plaintext as decrypt on equal inputs. But when key or iv are longer than they should normally be, aes_decrypt_mysql will stick to what MySQL’s aes_decrypt does: ‘fold’ key and ignore excess bits of IV.

Supported 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 — Initialization vector. Optional. String.

Returned value

• Decrypted String. String.

Examples

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)

Query:

SELECT aes_decrypt_mysql('aes-256-ofb', unhex('24E9E4966469'), '123456789101213141516171819202122', 'iviviviviviviviv123456') AS plaintext

Result:

┌─plaintext─┐
│ Secret    │
└───────────┘