Unicode 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.

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Unicode C

#include <C_CkEmailW.h>

void ChilkatSample(void)
    {
    BOOL success;
    HCkEmailW email;

    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.

    email = CkEmailW_Create();

    success = CkEmailW_LoadEml(email,L"qa_data/eml/signed.eml");
    if (success == FALSE) {
        wprintf(L"%s\n",CkEmailW_lastErrorText(email));
        CkEmailW_Dispose(email);
        return true;
    }

    if (CkEmailW_getReceivedSigned(email) == TRUE) {
        wprintf(L"This email was received with a digital signature.\n");
        if (CkEmailW_getSignaturesValid(email) == TRUE) {
            wprintf(L"All signatures are valid.\n");
        }
        else {
            wprintf(L"One or more signatures are NOT valid.\n");
        }

    }
    else {
        wprintf(L"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.


    CkEmailW_Dispose(email);

    }