PHP openssl_verify() Function

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The openssl_verify() function is an inbuilt function in PHP which is used to verifies that if the signature is correct for the specified data using the public key associated with public_key or not. This must be the public key corresponding to the private key used for signing.

Syntax:

openssl_verify( $data, $signature, 
    $public_key, $algorithm ): int|false

Parameters: This function accept four parameters which are listed below –

data: The string of data used to generate the signature previously.
signature: A raw binary string, generated by openssl_sign() or similar means.
public_key: string – a PEM formatted key, example, “—–BEGIN PUBLIC KEY—– MIIBCgK…”
algorithm: A valid string returned by openssl_get_md_methods() function.

Return Value: It returns 1 if the signature is correct, 0 if it is incorrect, and -1 or false on error.

Note: The public key comes from a certificate in any of the support formats.

Listed below are examples illustrating the use of openssl_verify() function:

Example 1:

PHP

<?php 
    
// Data you want to sign 
$data = 'zambiatek for zambiatek'; 
  
// Create a new pair of private and public key 
$private_key_rsa = openssl_pkey_new(array( 
    "private_key_bits" => 2048, 
    "private_key_type" => OPENSSL_KEYTYPE_RSA, 
)); 
  
$details = openssl_pkey_get_details($private_key_rsa); 
$public_key_rsa = openssl_pkey_get_public($details['key']); 
  
// Create signature for your data 
openssl_sign($data, $signature,  
    $private_key_rsa, "sha256WithRSAEncryption"); 
  
// Verify signature obtained for your data 
$result = openssl_verify($data, $signature,  
    $public_key_rsa, OPENSSL_ALGO_SHA256); 
  
if ($result == 1) { 
    echo "signature is valid for given data."; 
} elseif ($ok == 0) { 
    echo "signature is invalid for given data."; 
} else { 
    echo "error: ".openssl_error_string(); 
} 
  
?>

Output:

signature is valid for given data.

Example 2:

PHP

<?php 
    
// Data you want to sign 
$data = 'zambiatek for zambiatek'; 
  
// Create a new pair of private and public key 
$private_key_rsa = openssl_pkey_new(array( 
    "private_key_bits" => 2048, 
    "private_key_type" => OPENSSL_KEYTYPE_RSA, 
)); 
  
$details = openssl_pkey_get_details($private_key_rsa); 
$public_key_rsa = openssl_pkey_get_public($details['key']); 
  
// Create signature for your data 
openssl_sign($data, $signature,  
    $private_key_rsa, "sha256WithRSAEncryption"); 
  
// Change the data 
$data = 'zambiatek and zambiatek'; 
  
// Verify signature obtained for your data 
$result = openssl_verify($data, $signature,  
    $public_key_rsa, OPENSSL_ALGO_SHA256); 
  
if ($result == 1) { 
    echo "signature is valid for given data."; 
} elseif ($ok == 0) { 
    echo "signature is invalid for given data."; 
} else { 
    echo "error: ".openssl_error_string(); 
} 
?>