PHP ActiveX

Check if an Email Was Received Digitally Signed

Demonstrates the read-only Chilkat Email.ReceivedSigned property, which is true if the email was originally received carrying one or more digital signatures. Knowing a message was signed is separate from knowing the signature checked out, so this example also reads SignaturesValid to report whether the signed content verified.

Background: A digital signature on an email (S/MIME) provides two things: authenticity (it was really sent by the holder of a particular certificate) and integrity (the content was not altered in transit). The sender signs a hash of the message with their private key; the recipient verifies it with the sender's public certificate. ReceivedSigned simply tells you a signature is present — verifying it is a separate step exposed through SignaturesValid.

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<?php

$success = 0;

//  Demonstrates the read-only Email.ReceivedSigned property, which is true if this
//  email was originally received with a digital signature.  Use SignaturesValid to
//  determine whether the signed content actually verified.

$email = new COM("Chilkat.Email");

$success = $email->LoadEml('qa_data/eml/signed.eml');
if ($success == 0) {
    print $email->LastErrorText . "\n";
    exit;
}

if ($email->ReceivedSigned == 1) {
    print 'This email was received with a digital signature.' . "\n";
    if ($email->SignaturesValid == 1) {
        print 'All signatures are valid.' . "\n";
    }
    else {
        print 'One or more signatures are NOT valid.' . "\n";
    }

}
else {
    print 'This email was not signed.' . "\n";
}

//  Note: Paths such as "qa_data/..." are relative local filesystem paths,
//  relative to the current working directory of the running application.

?>