Question

I need to encrypt a stream with pgp using the bouncycastle provider. All of the examples I can find are about taking a plain text file and encrypting that however I won’t have a file and it’s important that the plain text never be written to disk.

Most of the methods I’ve seen are using

PGPUtil.writeFileToLiteralData which wants the plaintext passed in. I’d rather passin a byte[] or an inputStream.

Can someone point me to an example that

• starts from string/byte[]/inputstream
• encrypts said string/byte[] to an outputStrem that I can write to a file
• decrypts from an inputStream

In case anyone else stumbles upon this and wants the full solution

package com.common.security.pgp;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
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 java.util.Date;
import java.util.Iterator;

import org.bouncycastle.bcpg.ArmoredOutputStream;
import org.bouncycastle.jce.provider.BouncyCastleProvider;
import org.bouncycastle.openpgp.PGPCompressedData;
import org.bouncycastle.openpgp.PGPCompressedDataGenerator;
import org.bouncycastle.openpgp.PGPEncryptedData;
import org.bouncycastle.openpgp.PGPEncryptedDataGenerator;
import org.bouncycastle.openpgp.PGPEncryptedDataList;
import org.bouncycastle.openpgp.PGPException;
import org.bouncycastle.openpgp.PGPLiteralData;
import org.bouncycastle.openpgp.PGPLiteralDataGenerator;
import org.bouncycastle.openpgp.PGPObjectFactory;
import org.bouncycastle.openpgp.PGPPrivateKey;
import org.bouncycastle.openpgp.PGPPublicKey;
import org.bouncycastle.openpgp.PGPPublicKeyEncryptedData;
import org.bouncycastle.openpgp.PGPPublicKeyRing;
import org.bouncycastle.openpgp.PGPPublicKeyRingCollection;
import org.bouncycastle.openpgp.PGPSecretKey;
import org.bouncycastle.openpgp.PGPSecretKeyRingCollection;
import org.bouncycastle.openpgp.PGPUtil;

/**
 * Simple routine to encrypt and decrypt using a Public and Private key with passphrase. This service
 * routine provides the basic PGP services between byte arrays.
 * 
 */
public class PgpEncryption {


    private static PGPPrivateKey findSecretKey(
            PGPSecretKeyRingCollection pgpSec, long keyID, char[] pass)
            throws PGPException, NoSuchProviderException {
        PGPSecretKey pgpSecKey = pgpSec.getSecretKey(keyID);

        if (pgpSecKey == null) {
            return null;
        }

        return pgpSecKey.extractPrivateKey(pass, "BC");
    }

    /**
     * decrypt the passed in message stream
     * 
     * @param encrypted
     *            The message to be decrypted.
     * @param passPhrase
     *            Pass phrase (key)
     * 
     * @return Clear text as a byte array. I18N considerations are not handled
     *         by this routine
     * @exception IOException
     * @exception PGPException
     * @exception NoSuchProviderException
     */
    public static byte[] decrypt(byte[] encrypted, InputStream keyIn, char[] password)
            throws IOException, PGPException, NoSuchProviderException {
        InputStream in = new ByteArrayInputStream(encrypted);

        in = PGPUtil.getDecoderStream(in);

        PGPObjectFactory pgpF = new PGPObjectFactory(in);
        PGPEncryptedDataList enc = null;
        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;
        PGPSecretKeyRingCollection pgpSec = new PGPSecretKeyRingCollection(
                PGPUtil.getDecoderStream(keyIn));

        while (sKey == null && it.hasNext()) {
            pbe = (PGPPublicKeyEncryptedData) it.next();

            sKey = findSecretKey(pgpSec, pbe.getKeyID(), password);
        }

        if (sKey == null) {
            throw new IllegalArgumentException(
                    "secret key for message not found.");
        }

        InputStream clear = pbe.getDataStream(sKey, "BC");



        PGPObjectFactory pgpFact = new PGPObjectFactory(clear);

        PGPCompressedData cData = (PGPCompressedData) pgpFact.nextObject();

        pgpFact = new PGPObjectFactory(cData.getDataStream());

        PGPLiteralData ld = (PGPLiteralData) pgpFact.nextObject();

        InputStream unc = ld.getInputStream();

        ByteArrayOutputStream out = new ByteArrayOutputStream();
        int ch;

        while ((ch = unc.read()) >= 0) {
            out.write(ch);

        }

        byte[] returnBytes = out.toByteArray();
        out.close();
        return returnBytes;
    }

    /**
     * Simple PGP encryptor between byte[].
     * 
     * @param clearData
     *            The test to be encrypted
     * @param passPhrase
     *            The pass phrase (key). This method assumes that the key is a
     *            simple pass phrase, and does not yet support RSA or more
     *            sophisiticated keying.
     * @param fileName
     *            File name. This is used in the Literal Data Packet (tag 11)
     *            which is really inly important if the data is to be related to
     *            a file to be recovered later. Because this routine does not
     *            know the source of the information, the caller can set
     *            something here for file name use that will be carried. If this
     *            routine is being used to encrypt SOAP MIME bodies, for
     *            example, use the file name from the MIME type, if applicable.
     *            Or anything else appropriate.
     * 
     * @param armor
     * 
     * @return encrypted data.
     * @exception IOException
     * @exception PGPException
     * @exception NoSuchProviderException
     */
    public static byte[] encrypt(byte[] clearData, PGPPublicKey encKey,
            String fileName,boolean withIntegrityCheck, boolean armor)
            throws IOException, PGPException, NoSuchProviderException {
        if (fileName == null) {
            fileName = PGPLiteralData.CONSOLE;
        }

        ByteArrayOutputStream encOut = new ByteArrayOutputStream();

        OutputStream out = encOut;
        if (armor) {
            out = new ArmoredOutputStream(out);
        }

        ByteArrayOutputStream bOut = new ByteArrayOutputStream();

        PGPCompressedDataGenerator comData = new PGPCompressedDataGenerator(
                PGPCompressedDataGenerator.ZIP);
        OutputStream cos = comData.open(bOut); // open it with the final
        // destination
        PGPLiteralDataGenerator lData = new PGPLiteralDataGenerator();

        // we want to generate compressed data. This might be a user option
        // later,
        // in which case we would pass in bOut.
        OutputStream pOut = lData.open(cos, // the compressed output stream
                PGPLiteralData.BINARY, fileName, // "filename" to store
                clearData.length, // length of clear data
                new Date() // current time
                );
        pOut.write(clearData);

        lData.close();
        comData.close();

        PGPEncryptedDataGenerator cPk = new PGPEncryptedDataGenerator(
                PGPEncryptedData.CAST5, withIntegrityCheck, new SecureRandom(),
                "BC");

        cPk.addMethod(encKey);

        byte[] bytes = bOut.toByteArray();

        OutputStream cOut = cPk.open(out, bytes.length);

        cOut.write(bytes); // obtain the actual bytes from the compressed stream

        cOut.close();

        out.close();

        return encOut.toByteArray();
    }

    private static PGPPublicKey readPublicKey(InputStream in)
            throws IOException, PGPException {
        in = PGPUtil.getDecoderStream(in);

        PGPPublicKeyRingCollection pgpPub = new PGPPublicKeyRingCollection(in);

        //
        // we just loop through the collection till we find a key suitable for
        // encryption, in the real
        // world you would probably want to be a bit smarter about this.
        //

        //
        // iterate through the key rings.
        //
        Iterator rIt = pgpPub.getKeyRings();

        while (rIt.hasNext()) {
            PGPPublicKeyRing kRing = (PGPPublicKeyRing) rIt.next();
            Iterator kIt = kRing.getPublicKeys();

            while (kIt.hasNext()) {
                PGPPublicKey k = (PGPPublicKey) kIt.next();

                if (k.isEncryptionKey()) {
                    return k;
                }
            }
        }

        throw new IllegalArgumentException(
                "Can't find encryption key in key ring.");
    }

    public static byte[] getBytesFromFile(File file) throws IOException {
        InputStream is = new FileInputStream(file);

        // Get the size of the file
        long length = file.length();

        if (length > Integer.MAX_VALUE) {
            // File is too large
        }

        // Create the byte array to hold the data
        byte[] bytes = new byte[(int)length];

        // Read in the bytes
        int offset = 0;
        int numRead = 0;
        while (offset < bytes.length
               && (numRead=is.read(bytes, offset, bytes.length-offset)) >= 0) {
            offset += numRead;
        }

        // Ensure all the bytes have been read in
        if (offset < bytes.length) {
            throw new IOException("Could not completely read file "+file.getName());
        }

        // Close the input stream and return bytes
        is.close();
        return bytes;
    }

    public static void main(String[] args) throws Exception {
        Security.addProvider(new BouncyCastleProvider());


        byte[] original = "Hello world".getBytes();
        System.out.println("Starting PGP test");

        FileInputStream pubKey = new FileInputStream("/Users/me/pub.key");
        byte[] encrypted = encrypt(original, readPublicKey(pubKey), null,
                true, true);

        FileOutputStream dfis = new FileOutputStream("/Users/me/enc.asc");
        dfis.write(encrypted);
        dfis.close();

        byte[] encFromFile = getBytesFromFile(new File("/Users/me/enc.asc"));
        FileInputStream secKey = new FileInputStream("/Users/me/sec.key");

        System.out.println("\nencrypted data = '" + new String(encrypted) + "'");

        byte[] decrypted = decrypt(encFromFile, secKey, "passphrase".toCharArray());

        System.out.println("\ndecrypted data = '" + new String(decrypted) + "'");


    }
}

Answer 1

Looking at the source of PGPUtil you can see what API to call when working with streams or arrays directly:

public static void writeFileToLiteralData(OutputStream out,
               char fileType, File file, byte[] buffer) throws IOException {
   PGPLiteralDataGenerator lData = new PGPLiteralDataGenerator();
   OutputStream pOut = lData.open(out, fileType, file.getName(),
                   new Date(file.lastModified()), buffer);
   FileInputStream in = new FileInputStream(file);
   byte[] buf = new byte[buffer.length];
   int len;

   while ((len = in.read(buf)) > 0) {
         pOut.write(buf, 0, len);
   }

   lData.close();
   in.close();
}