Encrypt File to PKCS7 .p7m

PHP example to public-key encrypt a file creating a PKCS#7 .p7m file as output. Also demonstrates how to decrypt the .p7m to recover the original file.

Download Chilkat Crypt ActiveX

<?php

$crypt = new COM("Chilkat.Crypt2");

//  Any string argument automatically begins the 30-day trial.
$success = $crypt->UnlockComponent('30-day trial');
if ($success != true) {
    print $crypt->lastErrorText() . "\n";
    exit;
}

//  Indicate the public-key encryption is to be used.
//  Do this by setting the encryption algorithm equal
//  to "PKI" (an acroynm for public-key infrastructure).
$crypt->CryptAlgorithm = 'PKI';

//  Indicate the inner symmetric encryption algorithm to be used.
//  possible values are "aes", "des", "3des", and "rc2".
//  For this example, we'll use 256-bit AES encryption.
$crypt->Pkcs7CryptAlg = 'aes';
$crypt->KeyLength = 256;

//  To encrypt, only a certificate w/ public key is needed.
//  (The certificate w/ private key is required for decryption.)

//  The LoadFromFile method can load virtually any certificate format:
//  1. DER encoded binary X.509 (.CER)
//  2. Base-64 encoded X.509 (.CER)
//  3. Cryptographic Message Syntax Standard - PKCS #7 Certificates (.P7B)
//  4. PEM format
$encryptCert = new COM("Chilkat.Cert");
$success = $encryptCert->LoadFromFile('/Users/chilkat/testData/cer/acme.cer');
if ($success != true) {
    print $encryptCert->lastErrorText() . "\n";
    exit;
}

//  Tell the crypt object to use the certificate for encrypting:
$crypt->AddEncryptCert($encryptCert);

//  Encrypt a file, producing a .p7m as output.
//  The input file is unchanged, the output .p7m contains the encrypted
//  contents of the input file.
$inFile = '/Users/chilkat/testData/pdf/sample.pdf';
$outFile = '/Users/chilkat/testData/p7m/sample.pdf.p7m';
$success = $crypt->CkEncryptFile($inFile,$outFile);
if ($success != true) {
    print $crypt->lastErrorText() . "\n";
    exit;
}

//  For demonstration purposes, a different instance of the object will be used
//  for decryption.
$decrypt = new COM("Chilkat.Crypt2");

//  To decrypt, the certificate w/ private key is required.  A PFX (also known
//  as PKCS#12) is a common secure container for certs and private keys.
$pfxFilename = '/Users/chilkat/testData/pfx/acme.pfx';
$pfxPassword = 'secret';

//  Tell the component to look in the PFX file for certs and private keys.
$success = $decrypt->AddPfxSourceFile($pfxFilename,$pfxPassword);
if ($success != true) {
    print $decrypt->lastErrorText() . "\n";
    exit;
}

//  Tell the decrypt object that PKI (public key encryption) is to be used
//  for decryptiong.
$decrypt->CryptAlgorithm = 'PKI';
//  There is no need to set the Pkcs7Alg or KeyLength because this information
//  is contained within the .p7m

//  Decrypt the .p7m
$inFile = '/Users/chilkat/testData/p7m/sample.pdf.p7m';
$outFile = '/Users/chilkat/testData/pdf/recovered.pdf';
$success = $decrypt->CkDecryptFile($inFile,$outFile);
if ($success == false) {
    print $decrypt->lastErrorText() . "\n";
    exit;
}

print 'Success!' . "\n";
?>