PHP Extension

Select the S/MIME Encryption Algorithm

Demonstrates the Chilkat Email.Pkcs7CryptAlg property, which selects the underlying symmetric encryption algorithm used when an email is sent encrypted with PKCS#7 public-key (S/MIME) encryption. Possible values are aes, aes-gcm, des, 3des, and rc2; the default is aes. This example selects AES and pairs it with a 256-bit key length.

Background: S/MIME encryption is hybrid. The message body is encrypted with a fast symmetric algorithm (the one this property chooses, such as AES) using a randomly generated one-time key; then that one-time key is itself encrypted with each recipient's public key. This gives the speed of symmetric encryption with the key-distribution convenience of public-key cryptography. Modern choices like aes are strongly preferred — older options such as des and rc2 are considered weak.

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PHP Extension

<?php

include("chilkat.php");

//  Demonstrates the Email.Pkcs7CryptAlg property, which selects the symmetric encryption
//  algorithm used when an email is sent encrypted with PKCS#7 (S/MIME) public-key
//  encryption.  Possible values: aes, aes-gcm, des, 3des, rc2.  The default is aes.

$email = new CkEmail();
$email->put_Subject('Encrypted email');
$email->put_Body('This message will be S/MIME encrypted when sent.');

//  Select AES with a 256-bit key for the symmetric encryption.
$email->put_Pkcs7CryptAlg('aes');
$email->put_Pkcs7KeyLength(256);

print 'Pkcs7CryptAlg = ' . $email->pkcs7CryptAlg() . "\n";
print 'Pkcs7KeyLength = ' . $email->get_Pkcs7KeyLength() . "\n";

?>