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

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.

Chilkat Java Downloads Java Libs for Windows, MacOS, Linux, Alpine Linux, Solaris Java Libs for Android

import com.chilkatsoft.*;

public class ChilkatExample {

  static {
    try {
        System.loadLibrary("chilkat");
    } catch (UnsatisfiedLinkError e) {
      System.err.println("Native code library failed to load.\n" + e);
      System.exit(1);
    }
  }

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

    CkCrypt2 crypt = new CkCrypt2();

    // 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.

    CkCert cert = new CkCert();

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

    boolean success = cert.LoadFromSmartcard("");
    if (success != true) {
        System.out.println(cert.lastErrorText());
        return;
        }

    // Tell it to use the cert and private key we've loaded.
    success = crypt.SetSigningCert(cert);
    if (success != true) {
        System.out.println(crypt.lastErrorText());
        return;
        }

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

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

    // Create the opaque signature:
    String originalData = "This is the string to be signed.";
    String opaqueSig = crypt.opaqueSignStringENC(originalData);
    if (crypt.get_LastMethodSuccess() != true) {
        System.out.println(crypt.lastErrorText());
        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...

    CkCrypt2 vCrypt = new CkCrypt2();

    // 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.
    success = vCrypt.SetVerifyCert(cert);
    if (success != true) {
        System.out.println(vCrypt.lastErrorText());
        return;
        }

    vCrypt.put_EncodingMode("base64");
    vCrypt.put_Charset("utf-8");

    String extractedData = vCrypt.opaqueVerifyStringENC(opaqueSig);
    if (vCrypt.get_LastMethodSuccess() != true) {
        System.out.println(vCrypt.lastErrorText());
        return;
        }

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

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