Sign a File to Create a .p7s (Detached Signature)

C# example to create a detached signature file (.p7s) for any type file. The signature can be verified by calling VerifyP7S and passing the original filename and the .p7s filename.

Download: Chilkat .NET Assemblies

Chilkat.Crypt2 crypt = new Chilkat.Crypt2();

//  Any string argument automatically begins the 30-day trial.
bool success;
success = crypt.UnlockComponent("30-day trial");
if (success != true) {
    textBox1.Text += crypt.LastErrorText + "\r\n";
    return;
}

//  Use a digital certificate and private key from a PFX file (.pfx or .p12).
string signingCertSubject;
signingCertSubject = "Acme Inc";
string pfxFilename;
pfxFilename = "/Users/chilkat/testData/pfx/acme.pfx";
string pfxPassword;
pfxPassword = "test123";

Chilkat.CertStore certStore = new Chilkat.CertStore();
success = certStore.LoadPfxFile(pfxFilename,pfxPassword);
if (success != true) {
    textBox1.Text += certStore.LastErrorText + "\r\n";
    return;
}

Chilkat.Cert cert = null;
cert = certStore.FindCertBySubjectCN(signingCertSubject);
if (cert == null ) {
    textBox1.Text += "Failed to find certificate by subject common name." + "\r\n";
    return;
}

//  Tell the crypt component to use this cert.
crypt.SetSigningCert(cert);

//  We can sign any type of file, creating a .p7s as output:
string inFile;
inFile = "/Users/chilkat/testData/pdf/sample.pdf";
string sigFile;
sigFile = "/Users/chilkat/testData/p7s/sample.p7s";

success = crypt.CreateP7S(inFile,sigFile);
if (success == false) {
    textBox1.Text += crypt.LastErrorText + "\r\n";

    return;
}

success = crypt.VerifyP7S(inFile,sigFile);
if (success == false) {
    textBox1.Text += crypt.LastErrorText + "\r\n";

    return;
}

MessageBox.Show("Success!");