C++

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.

Chilkat C++ Downloads

Download Chilkat for C++

C++

#include <CkEmail.h>

void ChilkatSample(void)
    {
    bool success = false;

    //  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.

    CkEmail email;

    success = email.LoadEml("qa_data/eml/signed.eml");
    if (success == false) {
        std::cout << email.lastErrorText() << "\r\n";
        return true;
    }

    if (email.get_ReceivedSigned() == true) {
        std::cout << "This email was received with a digital signature." << "\r\n";
        if (email.get_SignaturesValid() == true) {
            std::cout << "All signatures are valid." << "\r\n";
        }
        else {
            std::cout << "One or more signatures are NOT valid." << "\r\n";
        }

    }
    else {
        std::cout << "This email was not signed." << "\r\n";
    }

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