(PHP ActiveX) Encrypt a file to a PKCS7 encrypted message using multiple certificates from different users

Demonstrates how to encrypt a file to a PKCS7 encrypted message using multiple certificates from different users. Any one of the users can decrypt using his/her own certificate + private key.

Note: When doing public key encryption, it is the public key that is used to encrypt. The private key is required for decryption.

Chilkat ActiveX Downloads ActiveX for 32-bit and 64-bit Windows Note: The php_com_dotnet.dll may need to be enabled inside of php.ini.

<?php

// This example requires the Chilkat Crypt API to have been previously unlocked.
// See Unlock Chilkat Crypt for sample code.

// For versions of Chilkat < 10.0.0, use new COM('Chilkat_9_5_0.Chilkat.Crypt2')
$crypt = new COM("Chilkat.Crypt2");

// Tell the crypt object to use 3 certificates.
// Do this by calling AddEncryptCert for each certificate.

// Load a digital certificate. 
// We don't need the private key for encryption.
// Only the public key is needed (which is included in a certificate).
// For versions of Chilkat < 10.0.0, use new COM('Chilkat_9_5_0.Chilkat.Cert')
$cert1 = new COM("Chilkat.Cert");
$success = $cert1->LoadFromFile('qa_data/user1/cert_user1.pem');
// Assume success for the example, but make sure your application checks for success/failure...
$crypt->AddEncryptCert($cert1);

// For versions of Chilkat < 10.0.0, use new COM('Chilkat_9_5_0.Chilkat.Cert')
$cert2 = new COM("Chilkat.Cert");
$success = $cert2->LoadFromFile('qa_data/user2/cert_user2.pem');
$crypt->AddEncryptCert($cert2);

// For versions of Chilkat < 10.0.0, use new COM('Chilkat_9_5_0.Chilkat.Cert')
$cert3 = new COM("Chilkat.Cert");
$success = $cert3->LoadFromFile('qa_data/user3/cert_user3.pem');
$crypt->AddEncryptCert($cert3);

// Indicate that we want PKI encryption (i.e. public-key infrastructure)
// to produce a CMS message (Cryptographic Message Syntax/PKCS7),
// that is be created with RSAES-OAEP padding, SHA256, and AES-128 for the
// bulk encryption.
$crypt->CryptAlgorithm = 'pki';
$crypt->Pkcs7CryptAlg = 'aes';
$crypt->KeyLength = 128;
$crypt->OaepHash = 'sha256';
$crypt->OaepPadding = 1;

// Load the file to be encrypted...
// For versions of Chilkat < 10.0.0, use new COM('Chilkat_9_5_0.Chilkat.BinData')
$fileData = new COM("Chilkat.BinData");
$success = $fileData->LoadFile('qa_data/jpg/penguins.jpg');
// Your app should check for success/failure..

// Encrypt the data.  The contents of the fileData object are replaced with the PKCS7 encrypted message.
$success = $crypt->EncryptBd($fileData);
if ($success != 1) {
    print $crypt->LastErrorText . "\n";
    exit;
}

// Save the PKCS7 encrypted message to a file..
$success = $fileData->WriteFile('qa_output/pkcs7_encrypted.p7');

// Now indicate that the PKCS7 output is to be returned in the base64 encoding.
$crypt->EncodingMode = 'base64';

print 'OK.' . "\n";

?>