Verify S/MIME Signature

C# example to verify an S/MIME signature and unwrap the S/MIME to get the original MIME prior to signing/encrypting.

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Chilkat.Mime mime = new Chilkat.Mime();

//  Any string argument automatically begins the 30-day trial.
bool success;
success = mime.UnlockComponent("30-day trial");
if (success != true) {
    MessageBox.Show("MIME component unlock failed");
    return;
}

//  Load an S/MIME message from a file:
success = mime.LoadMimeFile("signedMime.txt");
if (success != true) {
    MessageBox.Show(mime.LastErrorText);
    return;
}

//  The ContainsEncryptedParts/ContainsSignedParts methods
//  can be called to determine if the MIME is encrypted and/or signed:
bool isEncrypted;
isEncrypted = mime.ContainsEncryptedParts();
bool isSigned;
isSigned = mime.ContainsSignedParts();

//  We don't want the "unwrap extras".  You'll see what those
//  are in a few moments...
mime.UnwrapExtras = false;

//  To verify the signature, call UnwrapSecurity.  This will
//  verify the signature(s) and decrypt the S/MIME and restore
//  the MIME to the unsigned/unencrypted state.
//  The results of what was found are present in the MIME object's
//  properties, as well as extra header fields that are added
//  to the unwrapped MIME.
success = mime.UnwrapSecurity();
if (success != true) {
    //  UnwrapSecurity returns _TRUE_ if all signatures were
    //  verified and all parts decrypted.
    MessageBox.Show(mime.LastErrorText);
    return;
}

//  The mime.UnwrapExtras property controls whether or not
//  these additional fields are added to the unwrapped MIME:
// 
//  X-NumPartsSigned: 1
//  X-SignaturesValid: yes
//  X-NumPartsEncrypted: 1
//  X-Decrypted: no
// 
//  The X-NumPartsSigned/X-SignaturesValid headers are added
//  if the MIME was signed.
// 
//  The X-NumPartsEncrypted/X-Decrypted headers are added
//  if the MIME was encrypted.
// 

//  If the MIME was signed, get the certificate used for signing.
if (isSigned == true) {
    //  The NumSignerCerts property indicates how many certificates
    //  were used for signing.  This example will assume the value is 1.
    //  To get the 1st signer cert, call GetSignerCert with an index of 0:
    Chilkat.Cert signerCert;
    signerCert = mime.GetSignerCert(0);
    if (!(signerCert == null )) {
        textBox1.Text += "**** Signer Cert: "
             + signerCert.SubjectCN + "\r\n";
        textBox1.Refresh();
    }

}

//  If the MIME was encrypted, get the certificate used for encryption:
if (isEncrypted == true) {
    //  The NumEncryptCerts property indicates how many certificates
    //  were used for encrypting.  This example will assume the value is 1.
    //  To get the 1st encrypt cert, call GetEncryptCert with an index of 0:
    Chilkat.Cert encryptCert;
    encryptCert = mime.GetEncryptCert(0);
    if (!(encryptCert == null )) {
        textBox1.Text += "**** Encrypt Cert: "
             + encryptCert.SubjectCN + "\r\n";
        textBox1.Refresh();
    }

}

//  Display the unwrapped MIME:
textBox1.Text += mime.GetMime() + "\r\n";
textBox1.Refresh();

//  Save the unwrapped MIME to a file:
mime.SaveMime("unwrappedMime.txt");