Problem in enc/dec with DSA-Elgamal (keys generated using GNUPG utility)

Question

Hi all
Facing the problem in encryption/decryption using DSA-Elgamal (keys generated using GNUPG utility)
Steps followed
Generated a key pair using DSA and Elgamal (default) form GNUPG utility (size 1024)
Placed generated keys pubring.gpg & secring.gpg in the source directory where the code is executing but am getting the error
D:\test>c:\jdk\bin\java BouncyCastlePGPTest
Creating a temp file...
Temp file created at
D:\test\pgp
Reading the temp file to make sure that the bits were written
the message I want to encrypt
Get Public Key
Key Strength = 1024
Algorithm = 17
mohankumar (start) <[email protected]>
Key Count = 1
In Ecrypt File
creating comData...
comData created...
using PGPEncryptedDataGenerator...
111...
java.lang.IllegalArgumentException: passed in key not an encryption key!f
D:\test>
but the same code works fine if we try to encrypt using RSA generated keys
D:\test>c:\jdk\bin\java BouncyCastlePGPTest
Creating a temp file...
Temp file created at
D:\test\pgp
Reading the temp file to make sure that the bits were written
the message I want to encrypt
Get Public Key
Key Strength = 1024
Algorithm = 1
sriganesh (sriganesh) <[email protected]>
Key Count = 1
In Ecrypt File
creating comData...
comData created...
using PGPEncryptedDataGenerator...
used PGPEncryptedDataGenerator...
wrote bOut to byte array...
Reading the encrypted file
-----BEGIN PGP MESSAGE-----
Version: BCPG v1.31
hIwD7qqzP41CKpUBBACOnQE265ud3AuJ8zGx9TjUFyeSwZH+PZJhjGLBTkI7gKdh
/hIF1u/sCzubw+9Mt8dbS0V2uHiqQgkCHAYIQKoVmiN65s8sUsIS0q3cTtBudUnd
xIEiyegtvB8LEpzldU/XrSglh8h6MdhhcPql46BG+0vs6p/bUAOygNv5e/DGzck2
1wNvc2/u2ffBgEP4qfrJUcF9OlvVAm03aB0S6gP8cH4LVdo5K9Bwu3d71qNKsryP
mML16rkA
=lfxf
-----END PGP MESSAGE-----
Decrypted Data= the message I want to encrypt
no message integrity check
Code As follows
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;
import org.bouncycastle.openpgp.*;
import java.util.Iterator;
public class BouncyCastlePGPTest {
private static PGPPrivateKey findSecretKey(
                                                  InputStream keyIn,
                                                  long keyID,
                                                  char[] pass)
                                                  throws IOException, PGPException, NoSuchProviderException {
PGPSecretKeyRingCollection pgpSec = new PGPSecretKeyRingCollection(PGPUtil.getDecoderStream(keyIn));
PGPSecretKey pgpSecKey = pgpSec.getSecretKey(keyID);
if (pgpSecKey == null) {
return null;
return pgpSecKey.extractPrivateKey(pass, "BC");
private static void decryptFile(InputStream in, InputStream keyIn, char[] passwd) throws Exception
in = PGPUtil.getDecoderStream(in);
try {
PGPObjectFactory pgpF = new PGPObjectFactory(in);
PGPEncryptedDataList enc;
Object o = pgpF.nextObject();
// the first object might be a PGP marker packet.
if (o instanceof PGPEncryptedDataList)
enc = (PGPEncryptedDataList)o;
else
enc = (PGPEncryptedDataList)pgpF.nextObject();
// find the secret key
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();
if (message instanceof PGPLiteralData)
PGPLiteralData ld = (PGPLiteralData)message;
FileOutputStream fOut = new FileOutputStream(ld.getFileName());
InputStream unc = ld.getInputStream();
int ch;
System.out.print("\n\n\nDecrypted Data= ");
while ((ch = unc.read()) >= 0)
                         System.out.print(""+(char)ch);
fOut.write(ch);
System.out.println("\n\n\n");
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("message integrity check passed");
else
System.err.println("no message integrity check");
catch (PGPException e) {
System.err.println(e);
if (e.getUnderlyingException() != null) {
e.getUnderlyingException().printStackTrace();
     public static void main(String[] args) {
          // the keyring that holds the public key we're encrypting with
          String publicKeyFilePath = "D:\\test\\pubring.gpg"; //D:\\test\\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("pgp");//File.createTempFile("pgp", null);
               FileWriter writer = new FileWriter(outputfile);
               writer.write("the message I want to encrypt".toCharArray());
               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
               FileOutputStream out = new FileOutputStream(outputfile.getAbsolutePath() + ".asc");
               // 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);
//FileInputStream in = new FileInputStream(args[1]);
          FileInputStream in2 = new FileInputStream("d:\\test\\pgp.asc");
     FileInputStream keyIn = new FileInputStream("d:\\test\\secring.gpg");
     decryptFile(in2, keyIn, "test123".toCharArray());
          } 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 {
          System.out.println("Get Public Key");
          try {
               PGPPublicKeyRing pgpPub = new PGPPublicKeyRing(in);
               Iterator itr = pgpPub.getPublicKeys();
               PGPPublicKey pk = null;
               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
          try {
System.out.println("In Ecrypt File");
          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();
          } catch (IOException ex) {
               System.out.println("IOException\t" +ex.toString());
          } catch (NoSuchProviderException ex1) {
               System.out.println("NoSuchProviderException\t" +ex1.toString());
          } catch (PGPException ex2) {
               System.out.println("PGPException\t" +ex2.toString());
}

Answer 1

First - you're responding to a year-old message. I doubt the OP is still around.
Second - DSA is a Digital Signature Algorithm. The error tells you exactly what the problem is - DSA is not an encryption algorithm, and can't be used as one.
Grant