Encryption and Hashing Functions

Encryption and hashing functions in MySQL are used for data security and integrity purposes. Encryption functions are used to encrypt data so that it can be decrypted later, while hashing functions are used to create irreversible one-way hashes of data. Here is a list of common encryption and hashing functions, along with real-time examples and detailed explanations for each:

Encryption Functions:

AES_ENCRYPT() and AES_DECRYPT():
- AES_ENCRYPT() encrypts data using the Advanced Encryption Standard (AES), and AES_DECRYPT() decrypts the encrypted data.
Example (Encryption):
```
sqlCopy code
SELECT AES_ENCRYPT('sensitive_data', 'encryption_key') AS encrypted_data;
```
Output: The encrypted_data column will contain the encrypted value.

Example (Decryption):
```
sqlCopy code
SELECT AES_DECRYPT(encrypted_data, 'encryption_key') AS decrypted_data FROM table_name;
```
Output: The decrypted_data column will contain the decrypted value.
ENCRYPT():
- ENCRYPT() is used to encrypt a string using the Unix crypt() system call.
Example:
```
sqlCopy code
SELECT ENCRYPT('secret_password') AS encrypted_password;
```
Output: The encrypted_password column will contain the encrypted password.

Hashing Functions:

MD5():
- MD5() computes the MD5 hash of a string, producing a 32-character hexadecimal number.
Example:
```
sqlCopy code
SELECT MD5('hello_world') AS md5_hash;
```
Output: The md5_hash column will contain the MD5 hash value.
SHA1():
- SHA1() calculates the SHA-1 hash of a string, producing a 40-character hexadecimal number.
Example:
```
sqlCopy code
SELECT SHA1('secure_data') AS sha1_hash;
```
Output: The sha1_hash column will contain the SHA-1 hash value.
SHA2():
- SHA2() computes the SHA-2 hash of a string with a specified bit length (e.g., 256 or 512 bits).
Example:
```
sqlCopy code
SELECT SHA2('data_to_hash', 256) AS sha256_hash;
```
Output: The sha256_hash column will contain the SHA-256 hash value.
PASSWORD() (MySQL-specific):
- PASSWORD() is used to hash a password for use in the MySQL authentication system.
Example:
```
sqlCopy code
SELECT PASSWORD('user_password') AS hashed_password;
```
Output: The hashed_password column will contain the hashed password.

Hashing functions are commonly used to store passwords securely and to check the integrity of data. They produce a fixed-size hash value regardless of the input size, making them suitable for data validation and password storage. Encryption functions, on the other hand, allow you to protect sensitive data while still being able to retrieve and decrypt it when necessary.