# AES\$1DECRYPT function
<a name="AES_DECRYPT"></a>

The AES\$1DECRYPT function is used for decrypting data using the Advanced Encryption Standard (AES) algorithm.

## Syntax
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```
aes_decrypt(expr, key[, mode[, padding[, aad]]])
```

## Arguments
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 *expr*   
The binary value to decrypt.

 *key*   
The passphrase to use to decrypt the data.  
The passphrase must match the key originally used to produce the encrypted value and be 16, 24, or 32 bytes long.

 *mode*   
Specifies which block cipher mode should be used to decrypt messages.   
Valid modes: ECB, GCM, CBC.

 *padding*   
Specifies how to pad messages whose length isn't a multiple of the block size.   
Valid values: PKCS, NONE, DEFAULT.   
The DEFAULT padding means PKCS for ECB, NONE for GCM and PKCS for CBC.

 *aad*   
Optional additional authenticated data (AAD). Only supported for GCM mode. This can be any free-form input and must be provided for both encryption and decryption.

## Return type
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Returns a decrypted value of *expr* using AES in mode with padding.

## Examples
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The following example demonstrates how to use the Spark SQL AES\$1ENCRYPT function to securely encrypt a string of data (in this case, the word "Spark") using a specified encryption key. The resulting ciphertext is then Base64-encoded to make it easier to store or transmit. 

```
SELECT base64(aes_encrypt('Spark', 'abcdefghijklmnop'));
  4A5jOAh9FNGwoMeuJukfllrLdHEZxA2DyuSQAWz77dfn
```

The following example demonstrates how to use the Spark SQL AES\$1DECRYPT function to decrypt data that has been previously encrypted and Base64-encoded. The decryption process requires the correct encryption key and parameters (encryption mode and padding mode) to successfully recover the original plaintext data.

```
SELECT aes_decrypt(unbase64('3lmwu+Mw0H3fi5NDvcu9lg=='), '1234567890abcdef', 'ECB', 'PKCS');
 Spark SQL
```