C#

Create and Verify an Opaque PKCS7/CMS Signature

See more Digital Signatures Examples

Demonstrates how to create a PKCS7 opaque signature, and also how to verify an opaque signature. An opaque signature is different than a detached PKCS7 signature in that it contains the original data. Verifying an opaque signature retrieves the original content. C#

bool success = false;

//  This example assumes the Chilkat API to have been previously unlocked.
//  See Global Unlock Sample for sample code.

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

//  A certificate and private key is needed to create a signature.
//  Chilkat provides many different ways to load a certificate and private key, such
//  as from a PFX/.p12, Java keystore, JWK, Windows registry-based certificate stores, and other sources.
//  This example will load the certificate from a .crt and the private key from a .key file

Chilkat.Cert cert = new Chilkat.Cert();
//  The LoadFromFile method will automatically detect the format and load it.
success = cert.LoadFromFile("qa_data/certs/test_12345678a.cer");
if (success != true) {
    Debug.WriteLine(cert.LastErrorText);
    return;
}

//  Our private key is in an encrypted PKCS8 format.
//  If you don't know the format of your key, but you do know it's encrypted,
//  and requires a password, then just call any of the Chilkat methods that load
//  a private key w/ a password argument.  Chilkat will auto-detect the format
//  and load it correctly even if it's not the format indicated by the method name..
Chilkat.PrivateKey privKey = new Chilkat.PrivateKey();
string password = "12345678a";
success = privKey.LoadPkcs8EncryptedFile("qa_data/certs/test_12345678a.key",password);
if (success != true) {
    Debug.WriteLine(privKey.LastErrorText);
    return;
}

//  Set properties required for signing.

//  Tell it to use the cert and private key we've loaded.
success = crypt.SetSigningCert2(cert,privKey);
if (success != true) {
    Debug.WriteLine(crypt.LastErrorText);
    return;
}

//  Indicate we want the opaque signature in base64 format:
crypt.EncodingMode = "base64";

//  Sign the string using the "utf-8" byte representation:
crypt.Charset = "utf-8";

//  Create the opaque signature:
string originalData = "This is the string to be signed.";
string opaqueSig = crypt.OpaqueSignStringENC(originalData);
if (crypt.LastMethodSuccess != true) {
    Debug.WriteLine(crypt.LastErrorText);
    return;
}

Debug.WriteLine(opaqueSig);

//  The output looks like this:
//  MIIPgQYJKoZIhvcNAQcCoIIPcjCCD24CAQExCzAJBgUrDgMCGgUAMC8GCSqGSIb3DQEHAaAiBCBUaGlzIGlzIHRoZSBzdHJpbmcgdG8gYmUgc...

//  ----------------------------------------------------------------------------------------------
//  Now let's verify the signature and retrieve the original data.
//  We'll use a new Crypt2 object to keep things completely separate...

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

vCrypt.EncodingMode = "base64";
vCrypt.Charset = "utf-8";

string extractedData = vCrypt.OpaqueVerifyStringENC(opaqueSig);
if (vCrypt.LastMethodSuccess != true) {
    Debug.WriteLine(vCrypt.LastErrorText);
    return;
}

Debug.WriteLine("The extracted data: " + extractedData);

//  The output is:
//  The extracted data: This is the string to be signed.