(Android™) Extract PKCS7 Signature Digest

Demonstrates how to extract a signature digest from a PKCS7 signature.

Chilkat Android™ Downloads Android™ Java Libraries Android C/C++ Libraries

// Important: Don't forget to include the call to System.loadLibrary
// as shown at the bottom of this code sample.
package com.test;

import android.app.Activity;
import com.chilkatsoft.*;

import android.widget.TextView;
import android.os.Bundle;

public class SimpleActivity extends Activity {

  private static final String TAG = "Chilkat";

  // Called when the activity is first created.
  @Override
  public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    // This example requires the Chilkat Crypt API to have been previously unlocked.
    // See Unlock Chilkat Crypt for sample code.

    CkCrypt2 crypt = new CkCrypt2();

    String p7mFile = "qa_data/p7m/test.pdf.p7m";
    String outPath = "qa_output/test.pdf";

    // First let's see if this .p7m signature can be verified, and the original file extracted.
    boolean verified = crypt.VerifyP7M(p7mFile,outPath);
    if (verified != true) {
        Log.i(TAG, crypt.lastErrorText());
        return;
        }

    // How many signers?
    // (The NumSignerCerts property is set whenever a signature is verified.)
    Log.i(TAG, "Num Signers: " + String.valueOf(crypt.get_NumSignerCerts()));

    // Load the .p7m into memory...
    CkBinData pkcs7Data = new CkBinData();
    pkcs7Data.LoadFile(p7mFile);

    // Check to see if this .p7m contains the binary bytes, or if it's
    // already base64 encoded.  Get the 1st two bytes.  If the first two 
    // bytes are the us-ascii values "MI", then we have base64.
    CkStringBuilder sbBase64 = new CkStringBuilder();
    String hexStr = pkcs7Data.getEncodedChunk(0,2,"hex");
    sbBase64.Append(hexStr);

    boolean bHaveBase64 = false;
    if (sbBase64.ContentsEqual("4D49",true) == true) {
        bHaveBase64 = true;
        sbBase64.Clear();
        sbBase64.AppendBd(pkcs7Data,"utf-8",0,0);
        }

    // Get each signer's signature digest.
    crypt.put_EncodingMode("base64");
    int i = 0;
    String digest;
    while (i < crypt.get_NumSignerCerts()) {
        if (bHaveBase64) {
            digest = crypt.pkcs7ExtractDigest(i,sbBase64.getAsString());
            }
        else {
            digest = crypt.pkcs7ExtractDigest(i,pkcs7Data.getEncoded("base64"));
            }

        if (crypt.get_LastMethodSuccess() != true) {
            Log.i(TAG, crypt.lastErrorText());
            return;
            }

        Log.i(TAG, "Signer " + String.valueOf(i + 1) + " digest = " + digest);
        i = i + 1;
        }


  }

  static {
      System.loadLibrary("chilkat");

      // Note: If the incorrect library name is passed to System.loadLibrary,
      // then you will see the following error message at application startup:
      //"The application <your-application-name> has stopped unexpectedly. Please try again."
  }
}