Java

A3/A4 Certificate to Create and Verify an Opaque PKCS7/CMS Signature

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Demonstrates how to use an A3 or A4 certificate w/ private key on a smartcard or token 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.

Chilkat2 Java

import com.chilkatsoft.chilkat2.Cert;
import com.chilkatsoft.chilkat2.ChilkatException;
import com.chilkatsoft.chilkat2.Crypt2;

public class ChilkatExample {

    public static void main(String[] args) {
        // This example assumes the Chilkat API to have been previously unlocked.
        // See Global Unlock Sample for sample code.

        Crypt2 crypt = new 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 smartcards and hardware tokens, PFX/.p12, Java keystore, JWK, Windows registry-based certificate stores, and other sources.
        // This example will load the default certificate from the smartcard that is currently in
        // the smartcard reader.

        Cert cert = new Cert();

        // If the smartcard or token requires a PIN, we can set it here to avoid the dialog...
        cert.setSmartCardPin("000000");

        try {
            cert.loadFromSmartcard("");

            // Tell it to use the cert and private key we've loaded.
            crypt.setSigningCert(cert);
        } catch (ChilkatException e) {
            System.out.println(e.getLastErrorText());
            return;
        }

        // Indicate we want the opaque signature in base64 format:
        crypt.setEncodingMode("base64");

        // Sign the string using the "utf-8" byte representation:
        crypt.setCharset("utf-8");

        // Create the opaque signature:
        String originalData = "This is the string to be signed.";
        String opaqueSig;
        try {
            opaqueSig = crypt.opaqueSignStringENC(originalData);
        } catch (ChilkatException e) {
            System.out.println(e.getLastErrorText());
            return;
        }

        System.out.println(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...

        Crypt2 vCrypt = new Crypt2();

        // We only need the certificate to verify a signature (and extract the data from
        // an opaque signature).  The public key is always embedded within a certificate.
        String extractedData;
        try {
            vCrypt.setVerifyCert(cert);

            vCrypt.setEncodingMode("base64");
            vCrypt.setCharset("utf-8");

            extractedData = vCrypt.opaqueVerifyStringENC(opaqueSig);
        } catch (ChilkatException e) {
            System.out.println(e.getLastErrorText());
            return;
        }

        System.out.println("The extracted data: " + extractedData);

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