Sign with .pfx to create .p7s, Verify with .cer

Download: Chilkat .NET Assemblies

C# example to sign a file using a .pfx and creating a .p7s file as output. It then uses a .cer file to verify the signature.

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) {
    MessageBox.Show("Crypt component unlock failed");
    return;
}

Chilkat.CertStore certStore = new Chilkat.CertStore();
success = certStore.LoadPfxFile("chilkat.pfx","myPfxPassword");
if (success != true) {
    MessageBox.Show(certStore.LastErrorText);
    return;
}

Chilkat.Cert cert = null;
cert = certStore.FindCertBySubjectCN("Chilkat Software, Inc.");
if (cert == null ) {
    MessageBox.Show("Failed to find certificate");
    return;
}

//  We can explicitly choose hash/encryption algorithms using a CSP.
Chilkat.Csp csp = new Chilkat.Csp();
csp.SetProviderMicrosoftEnhanced();
csp.SetHashAlgorithm("sha-1");

//  Tell the crypt component to use this cert and this CSP.
crypt.SetSigningCert(cert);
crypt.SetCSP(csp);

//  We can sign any type of file, creating a .p7s as output:
success = crypt.CreateP7S("hamlet.xml","hamlet.p7s");
if (success == true) {
    MessageBox.Show("Signature created.");
}
else {
    MessageBox.Show(crypt.LastErrorText);
}

//  Verify and restore the original file:
//  Use a cert from a .cer file (which only contains the public key)
Chilkat.Cert cert2 = new Chilkat.Cert();
success = cert2.LoadFromFile("chilkat.cer");
if (success != true) {
    MessageBox.Show(cert2.LastErrorText);
    return;
}

crypt.SetVerifyCert(cert2);

success = crypt.VerifyP7S("hamlet.xml","hamlet.p7s");
if (success == true) {
    MessageBox.Show("Signature verified.");
}
else {
    MessageBox.Show(crypt.LastErrorText);
}