Encrypt a zip file using PGP in java

[sarada bokka]

Hi All,

I tried doing PGP encryption for a file using "PGP Encryption using Bouncy Castle" (http://cephas.net/blog/2004/04/01/pgp-encryption-using-bouncy-castle/) and it is working fine.

I would like to have the same kind of PGP encrypting for a zip file using java.

Could some one throw your thought's in achieving this.

[Ulf Dittmer]

Why do you think encrypting a ZIP file would be different than encrypting any other kind of file?

[sarada bokka]

I tried to encrypt the xip file as normal file

But after decrypting I am unable to unzip the file and throws "cannot open decrypttest.zip file as archive"

Encryption source

import java.io.BufferedReader;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.security.NoSuchProviderException;
import java.security.SecureRandom;
import java.security.Security;
import org.bouncycastle.bcpg.ArmoredOutputStream;
import org.bouncycastle.jce.provider.BouncyCastleProvider;
import org.bouncycastle.openpgp.PGPCompressedDataGenerator;
import org.bouncycastle.openpgp.PGPEncryptedDataGenerator;
import org.bouncycastle.openpgp.PGPException;
import org.bouncycastle.openpgp.PGPLiteralData;
import org.bouncycastle.openpgp.PGPPublicKey;
import org.bouncycastle.openpgp.PGPPublicKeyRing;
import org.bouncycastle.openpgp.PGPUtil;


public class BouncyCastlePGPTest {

	public static void main(String[] args) {
		
		// the keyring that holds the public key we're encrypting with
		String publicKeyFilePath = "C:\\TEMP\\New Folder (2)\\PGP\\pubring.pkr";
		
		// init the security provider
		Security.addProvider(new BouncyCastleProvider());
		
		try {
			
			System.out.println("Creating a temp file...");
			
			// create a file and write the string to it
			File outputfile = new File("encrypttest");
			FileWriter writer = new FileWriter(outputfile);
			//writer.write("the message I want to encrypt".toCharArray());
			//writer.close();
			
			FileReader fr = new FileReader("test.zip");
			BufferedReader br = new BufferedReader(fr);
			String s;
			while((s = br.readLine()) != null) {
				writer.write(s);
			}
			fr.close(); 
			writer.close();
			System.out.println("Temp file created at ");
			System.out.println(outputfile.getAbsolutePath());
			System.out.println("Reading the temp file to make sure that the bits were written\n----------------------------");
			
			BufferedReader isr = new BufferedReader(new FileReader(outputfile));
			String line = "";
			while ((line = isr.readLine()) != null) {
				System.out.println(line + "\n");
			}
			
			// read the key 
			FileInputStream	in = new FileInputStream(publicKeyFilePath);
			PGPPublicKey key = readPublicKey(in);
			
			// find out a little about the keys in the public key ring
			System.out.println("Key Strength = " + key.getBitStrength());
			System.out.println("Algorithm = " + key.getAlgorithm());
			
			int count = 0;
			for (java.util.Iterator iterator = key.getUserIDs(); iterator.hasNext();) {
				count++;
				System.out.println((String)iterator.next());	
			}
			System.out.println("Key Count = " + count);
			// create an armored ascii file
			System.out.println(">>>>"+outputfile.getAbsolutePath());
			FileOutputStream out = new FileOutputStream(outputfile.getAbsolutePath() + ".zip");
		
			// encrypt the file
			encryptFile(outputfile.getAbsolutePath(), out, key);
			
			System.out.println("Reading the encrypted file\n----------------------------");
			BufferedReader isr2 = new BufferedReader(new FileReader(new File(outputfile.getAbsolutePath() + ".asc")));
			String line2 = "";
			while ((line2 = isr2.readLine()) != null) {
				System.out.println(line2);
			}
			
			
				
		} catch (PGPException e) {
			System.out.println(e.toString());
			System.out.println(e.getUnderlyingException().toString());
			
		} catch (Exception e) {
			System.out.println(e.toString());
		}
		
	}
	
	private static PGPPublicKey readPublicKey(InputStream in) throws IOException {
		try {
			PGPPublicKeyRing pgpPub = new PGPPublicKeyRing(in);
			return pgpPub.getPublicKey();
		} catch (IOException io) {
			System.out.println("readPublicKey() threw an IOException");
			System.out.println(io.toString());
			throw io;
		}

	}
	
	private static void encryptFile(String fileName, OutputStream out, PGPPublicKey encKey)
	throws IOException, NoSuchProviderException, PGPException  
	{
			
		out = new ArmoredOutputStream(out);
		
		ByteArrayOutputStream bOut = new ByteArrayOutputStream();
		
		System.out.println("creating comData...");
		
		// get the data from the original file 
		PGPCompressedDataGenerator comData = new PGPCompressedDataGenerator(PGPCompressedDataGenerator.ZIP);
		PGPUtil.writeFileToLiteralData(comData.open(bOut), PGPLiteralData.BINARY, new File(fileName));
		comData.close();
		
		System.out.println("comData created...");
		
		System.out.println("using PGPEncryptedDataGenerator...");
		
		// object that encrypts the data
		PGPEncryptedDataGenerator cPk = new PGPEncryptedDataGenerator(PGPEncryptedDataGenerator.CAST5, new SecureRandom(), "BC");
		cPk.addMethod(encKey);
		
		System.out.println("used PGPEncryptedDataGenerator...");
		
		// take the outputstream of the original file and turn it into a byte array
		byte[] bytes = bOut.toByteArray();
		
		System.out.println("wrote bOut to byte array...");
		
		// write the plain text bytes to the armored outputstream
		OutputStream cOut = cPk.open(out, bytes.length);
		cOut.write(bytes);
		
		
		// cOut.close();
		cPk.close();
	
		out.close();	
	}
}

Decryption source

import org.bouncycastle.openpgp.*;


import org.bouncycastle.jce.provider.BouncyCastleProvider;
 
 
 
import java.io.*;
import java.util.Iterator;
import java.security.NoSuchProviderException;
import java.security.Security;

public class Decryptsarada {
   public static  void main(String[] args){
        try{
        	Security.addProvider(new BouncyCastleProvider()); 
            FileInputStream privKey = 
            	new FileInputStream("C:\\TEMP\\New Folder (2)\\PGP\\secring.skr");
            InputStream file = new BufferedInputStream (new FileInputStream("encrypttest.zip"));
            System.out.println(decryptFile(file, privKey, "my pgp test".toCharArray()));
        } catch (Exception ex){
            ex.printStackTrace();
        }
    }
 
 
    private static String decryptFile(InputStream in, InputStream keyIn, char[] passwd) throws Exception {
        try {
            PGPObjectFactory pgpF = new PGPObjectFactory(PGPUtil.getDecoderStream(in));
            Object o = pgpF.nextObject();
            PGPEncryptedDataList enc = o instanceof  PGPEncryptedDataList ? (PGPEncryptedDataList) o :(PGPEncryptedDataList) pgpF.nextObject();
            Iterator it = enc.getEncryptedDataObjects();
            PGPPrivateKey sKey = null;
            PGPPublicKeyEncryptedData pbe = null;
 
            while (sKey == null && it.hasNext()) {
                pbe = (PGPPublicKeyEncryptedData) it.next();
                sKey =findSecretKey(keyIn, pbe.getKeyID(), passwd);
            }
            if (sKey == null) {
 
                throw new IllegalArgumentException("secret key for message not found.");
            }
 
            InputStream clear = pbe.getDataStream(sKey, "BC");
            PGPObjectFactory plainFact = new PGPObjectFactory(clear);
            Object message = plainFact.nextObject();
            if (message instanceof  PGPCompressedData) {
                PGPCompressedData cData = (PGPCompressedData) message;
                PGPObjectFactory pgpFact = new PGPObjectFactory(cData.getDataStream());
                message = pgpFact.nextObject();
            }
            
            File outputfile = new File("decrypttest.zip");
			FileWriter writer = new FileWriter(outputfile);
            ByteArrayOutputStream baos = new ByteArrayOutputStream();
            if (message instanceof PGPLiteralData) {
                PGPLiteralData ld = (PGPLiteralData) message;
                InputStream unc = ld.getInputStream();
                int ch;
                while ((ch = unc.read()) >= 0) {
                    baos.write(ch);
                    writer.write(ch);
                }
            } else if (message instanceof  PGPOnePassSignatureList) {
                throw new PGPException("encrypted message contains a signed message - not literal data.");
            } else {
                throw new PGPException("message is not a simple encrypted file - type unknown.");
            }
 
            if (pbe.isIntegrityProtected()) {
               if (!pbe.verify()) {
                    System.err.println("message failed integrity check");
               }
            } else {
                System.err.println("no message integrity check");
            }
            return baos.toString();
        } catch (PGPException e) {
            e.printStackTrace();
        }
        return null;
    }
 
    private static PGPPrivateKey findSecretKey(InputStream keyIn, long keyID, char[] pass) throws IOException, PGPException, NoSuchProviderException {
        PGPSecretKeyRingCollection pgpSec = new PGPSecretKeyRingCollection(PGPUtil.getDecoderStream(keyIn));
        System.out.println("pgpSec size="+pgpSec);
        System.out.println(keyID);
        PGPSecretKey pgpSecKey = pgpSec.getSecretKey(keyID);
        return pgpSecKey != null? pgpSecKey.extractPrivateKey(pass, "BC"): null;
    }
   
}

jar file required : bcprov-jdk15-147b01.jar,bcpg-jdk15-1.44.jar

Please advice me how to proceed?

[Ulf Dittmer]

ZIP files are binary data - you can't use Readers and Writers to work with them; you need to use Streams.