How do i decrypt a php file?

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.

<?php

$simple_string = "Welcome to GeeksforGeeks\n";

echo "Original String: " . $simple_string;

$ciphering = "AES-128-CTR";

$iv_length = openssl_cipher_iv_length($ciphering);

$options = 0;

$encryption_iv = '1234567891011121';

$encryption_key = "GeeksforGeeks";

$encryption = openssl_encrypt($simple_string, $ciphering,

            $encryption_key, $options, $encryption_iv);

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

$decryption_iv = '1234567891011121';

$decryption_key = "GeeksforGeeks";

$decryption=openssl_decrypt ($encryption, $ciphering, 

        $decryption_key, $options, $decryption_iv);

echo "Decrypted String: " . $decryption;

?>

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.

<?php

$simple_string = "Welcome to GeeksforGeeks";

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

$ciphering = "BF-CBC";

$iv_length = openssl_cipher_iv_length($ciphering);

$options = 0;

$encryption_iv = random_bytes($iv_length);

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

$encryption = openssl_encrypt($simple_string, $ciphering,

        $encryption_key, $options, $encryption_iv);

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

$decryption_iv = random_bytes($iv_length);

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

$decryption = openssl_decrypt ($encryption, $ciphering,

            $decryption_key, $options, $encryption_iv);

echo "Decrypted String: " . $decryption;

?>

Output:

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

References:

• https://www.php.net/manual/en/function.openssl-encrypt.php
• https://www.php.net/manual/en/function.openssl-decrypt.php

PHP is a server-side scripting language designed specifically for web development. You can learn PHP from the ground up by following this PHP Tutorial and PHP Examples.

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