docs/sql-manual/sql-functions/encrypt-digest-functions/sm4-decrypt.md

---
{
"title": "SM4_DECRYPT",
"language": "en"
}
---

<!-- 
Licensed to the Apache Software Foundation (ASF) under one
or more contributor license agreements.  See the NOTICE file
distributed with this work for additional information
regarding copyright ownership.  The ASF licenses this file
to you under the Apache License, Version 2.0 (the
"License"); you may not use this file except in compliance
with the License.  You may obtain a copy of the License at
  http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing,
software distributed under the License is distributed on an
"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
KIND, either express or implied.  See the License for the
specific language governing permissions and limitations
under the License.
-->


### Description
#### Syntax

`VARCHAR SM4_DECRYPT(VARCHAR str, VARCHAR key_str[, VARCHAR init_vector][, VARCHAR encryption_mode])`

Returns the decrypted result, where:
- `str` is the text to be decrypted;
- `key_str` is the key. Note that this key is not a hexadecimal encoding, but a string representation of the encoded key. For example, for 128-bit key encryption, `key_str` should be 16-length. If the key is not long enough, use **zero padding** to make it up. If it is longer than that, the final key is found using a cyclic xor method. For example, if the 128-bit key used by the algorithm finally is `key`, then `key[i] = key_str[i] ^ key_str[i+128] ^ key_str[i+256] ^ ...`
- `init_vector` is the initial vector to be used in the algorithm, this is only valid for some algorithms, if not specified then Doris will use the built-in value;
- `encryption_mode` is the encryption algorithm, optionally available in variable.

### Example

```sql
mysql> set block_encryption_mode='';
Query OK, 0 rows affected (0.11 sec)

mysql> select SM4_DECRYPT(FROM_BASE64('aDjwRflBrDjhBZIOFNw3Tg=='),'F3229A0B371ED2D9441B830D21A390C3');
+--------------------------------------------------------------------------------+
| sm4_decrypt(from_base64('aDjwRflBrDjhBZIOFNw3Tg=='), '***', '', 'SM4_128_ECB') |
+--------------------------------------------------------------------------------+
| text                                                                           |
+--------------------------------------------------------------------------------+
1 row in set (0.19 sec)

MySQL> set block_encryption_mode="SM4_128_CBC";
Query OK, 0 rows affected (0.006 sec)

mysql> select SM4_DECRYPT(FROM_BASE64('FSYstvOmH2cXy7B/072Mug=='),'F3229A0B371ED2D9441B830D21A390C3');
+--------------------------------------------------------------------------------+
| sm4_decrypt(from_base64('FSYstvOmH2cXy7B/072Mug=='), '***', '', 'SM4_128_CBC') |
+--------------------------------------------------------------------------------+
| text                                                                           |
+--------------------------------------------------------------------------------+
1 row in set (0.11 sec)

MySQL > select SM4_DECRYPT(FROM_BASE64('G7yqOKfEyxdagboz6Qf01A=='),'F3229A0B371ED2D9441B830D21A390C3', '0123456789');
+--------------------------------------------------------------------------------------------------------+
| sm4_decrypt(from_base64('G7yqOKfEyxdagboz6Qf01A=='), 'F3229A0B371ED2D9441B830D21A390C3', '0123456789') |
+--------------------------------------------------------------------------------------------------------+
| text                                                                                                   |
+--------------------------------------------------------------------------------------------------------+
1 row in set (0.012 sec)
```

### Keywords
    SM4_DECRYPT, SM4, DECRYPT