How to Encrypt and Decrypt a PHP String ?

In PHP, Encryption and Decryption of a string is possible using one of the Cryptography Extensions called OpenSSL function for encrypt and decrypt.

openssl_encrypt() Function: The openssl_encrypt() function is used to encrypt the data.

Syntax:



string openssl_encrypt( string $data, string $method, string $key,
                        $options = 0, string $iv, string $tag= NULL,
                        string $aad, int $tag_length = 16  )

Parameters:

  • $data: It holds the string or data which need to be encrypted.
  • $method: The cipher method is adopted using openssl_get_cipher_methods() function.
  • $key: It holds the encryption key.
  • $options: It holds the bitwise disjunction of the flags OPENSSL_RAW_DATA and OPENSSL_ZERO_PADDING.
  • $iv: It holds the initialization vector which is not NULL.
  • $tag: It holds the authentication tag which is passed by reference when using AEAD cipher mode (GCM or CCM).
  • $aad: It holds the additional authentication data.
  • $tag_length: It holds the length of the authentication tag. The length of authentication tag lies between 4 to 16 for GCM mode.

Return Value: It returns the encrypted string on success or FALSE on failure.

openssl_decrypt() Function The openssl_decrypt() function is used to decrypt the data.

Syntax:

string openssl_decrypt( string $data, string $method, string $key,
             int $options = 0, string $iv, string $tag, string $aad)

Parameters:

  • $data: It holds the string or data which need to be encrypted.
  • $method: The cipher method is adopted using openssl_get_cipher_methods() function.
  • $key: It holds the encryption key.
  • $options: It holds the bitwise disjunction of the flags OPENSSL_RAW_DATA and OPENSSL_ZERO_PADDING.
  • $iv: It holds the initialization vector which is not NULL.
  • $tag: It holds the authentication tag using AEAD cipher mode (GCM or CCM). When authentication fails openssl_decrypt() returns FALSE.
  • $aad: It holds the additional authentication data.

Return Value: It returns the decrypted string on success or FALSE on failure.

Approach: First declare a string and store it into variable and use openssl_encrypt() function to encrypt the given string and use openssl_decrypt() function to descrypt the given string.

Example 1: This example illustrates the encryption and decryption of string.

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<?php
  
// Store a string into the variable which
// need to be Encrypted
$simple_string = "Welcome to GeeksforGeeks\n";
  
// Display the original string
echo "Original String: " . $simple_string;
  
// Store the cipher method
$ciphering = "AES-128-CTR";
  
// Use OpenSSl Encryption method
$iv_length = openssl_cipher_iv_length($ciphering);
$options = 0;
  
// Non-NULL Initialization Vector for encryption
$encryption_iv = '1234567891011121';
  
// Store the encryption key
$encryption_key = "GeeksforGeeks";
  
// Use openssl_encrypt() function to encrypt the data
$encryption = openssl_encrypt($simple_string, $ciphering,
            $encryption_key, $options, $encryption_iv);
  
// Display the encrypted string
echo "Encrypted String: " . $encryption . "\n";
  
// Non-NULL Initialization Vector for decryption
$decryption_iv = '1234567891011121';
  
// Store the decryption key
$decryption_key = "GeeksforGeeks";
  
// Use openssl_decrypt() function to decrypt the data
$decryption=openssl_decrypt ($encryption, $ciphering, 
        $decryption_key, $options, $decryption_iv);
  
// Display the decrypted string
echo "Decrypted String: " . $decryption;
  
?>

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Output:


Original String: Welcome to GeeksforGeeks
Encrypted String: hwB1K5NkfcIzkLTWQeQfHLNg5FlyX3PNUA==
Decrypted String: Welcome to GeeksforGeeks



Example 2: Below example illustrate the encryption and decryption of string. Here string to be encrypted and decrypted string will be same but the encrypted string is randomly changed respectively.











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<?php 


  


// Store a string into the variable which 


// need to be Encrypted 


$simple_string = "Welcome to GeeksforGeeks"; 


  


// Display the original string 


echo "Original String: " . $simple_string . "\n"; 


  


// Store cipher method 


$ciphering = "BF-CBC"; 


  


// Use OpenSSl encryption method 


$iv_length = openssl_cipher_iv_length($ciphering); 


$options = 0; 


  


// Use random_bytes() function which gives 


// randomly 16 digit values 


$encryption_iv = random_bytes($iv_length); 


  


// Alternatively, we can use any 16 digit 


// characters or numeric for iv 


$encryption_key = openssl_digest(php_uname(), 'MD5', TRUE); 


  


// Encryption of string process starts 


$encryption = openssl_encrypt($simple_string, $ciphering, 


        $encryption_key, $options, $encryption_iv); 


  


// Display the encrypted string 


echo "Encrypted String: " . $encryption . "\n"; 


  


// Decryption of string process starts 


// Used random_bytes() which gives randomly 


// 16 digit values 


$decryption_iv = random_bytes($iv_length); 


  


// Store the decryption key 


$decryption_key = openssl_digest(php_uname(), 'MD5', TRUE); 


  


// Descrypt the string 


$decryption = openssl_decrypt ($encryption, $ciphering, 


            $decryption_key, $options, $encryption_iv); 


  


// Display the decrypted string 


echo "Decrypted String: " . $decryption; 


  


?> 



















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Output:


Original String: Welcome to GeeksforGeeks
Encrypted String: hwB1K5NkfcIzkLTWQeQfHLNg5FlyX3PNUA==
Decrypted String: Welcome to GeeksforGeeks



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