I'm pretty familiar with PGP, and the way it works. I'd like to include some functionality in a project, but so far my research has left my head spinning. What I'd like to do is create a public key with a defined private pass phrase. From there, I'd share the public key with someone where they can then encrypt a message using the key and return it to me where I can decrypt. I envision the code looking something like this.
To generate my private pgp key:
PGPKey key = new PGPKey();
key.setPassPhrase("MySecretPassword!!!1");
key.generateRandomSharedKey();
key.build();
To encrypt I'd give my shared key to a friend:
String encryptedText = PGPTools.Encrypt("Text to encrypt", getSharedKey());
To decrypt the encrypted string after being sent back to me:
String decryptedText = PGPTools.Decrypt(encryptedText, key, "MySecretPassword!!!1")
Obviously I know I'm skipping out on a ton of details. Through my research I've seen references to libraries like Bouncy Castle and Spongy Castle. Any help would be hugely appreciated!
I want to post my solution because A. it was extremely difficult to get this working, and B. If any crypto pro's want to audit my code I'd be eternally grateful.
I included the 4 following libraries:
compile 'com.madgag.spongycastle:core:1.50.0.0'
compile 'com.madgag.spongycastle:pg:1.50.0.0'
compile 'com.madgag.spongycastle:pkix:1.50.0.0'
compile 'com.madgag.spongycastle:prov:1.50.0.0'
Bouncy Castle needs to be added as a security provider. I included this code in a class that initializes some other objects when the app loads.
static {
Security.addProvider(new BouncyCastleProvider());
}
Here's the utils class I created that really contains the nuts and bolts. Edited slightly:
import com.example.Device;
import org.spongycastle.bcpg.ArmoredInputStream;
import org.spongycastle.bcpg.ArmoredOutputStream;
import org.spongycastle.bcpg.HashAlgorithmTags;
import org.spongycastle.bcpg.SymmetricKeyAlgorithmTags;
import org.spongycastle.bcpg.sig.Features;
import org.spongycastle.bcpg.sig.KeyFlags;
import org.spongycastle.crypto.generators.RSAKeyPairGenerator;
import org.spongycastle.crypto.params.RSAKeyGenerationParameters;
import org.spongycastle.openpgp.PGPCompressedData;
import org.spongycastle.openpgp.PGPCompressedDataGenerator;
import org.spongycastle.openpgp.PGPEncryptedData;
import org.spongycastle.openpgp.PGPEncryptedDataGenerator;
import org.spongycastle.openpgp.PGPEncryptedDataList;
import org.spongycastle.openpgp.PGPException;
import org.spongycastle.openpgp.PGPKeyPair;
import org.spongycastle.openpgp.PGPKeyRingGenerator;
import org.spongycastle.openpgp.PGPLiteralData;
import org.spongycastle.openpgp.PGPLiteralDataGenerator;
import org.spongycastle.openpgp.PGPObjectFactory;
import org.spongycastle.openpgp.PGPPrivateKey;
import org.spongycastle.openpgp.PGPPublicKey;
import org.spongycastle.openpgp.PGPPublicKeyEncryptedData;
import org.spongycastle.openpgp.PGPPublicKeyRing;
import org.spongycastle.openpgp.PGPSecretKey;
import org.spongycastle.openpgp.PGPSecretKeyRing;
import org.spongycastle.openpgp.PGPSignature;
import org.spongycastle.openpgp.PGPSignatureSubpacketGenerator;
import org.spongycastle.openpgp.PGPUtil;
import org.spongycastle.openpgp.operator.PBESecretKeyDecryptor;
import org.spongycastle.openpgp.operator.PBESecretKeyEncryptor;
import org.spongycastle.openpgp.operator.PGPDigestCalculator;
import org.spongycastle.openpgp.operator.bc.BcPBESecretKeyDecryptorBuilder;
import org.spongycastle.openpgp.operator.bc.BcPBESecretKeyEncryptorBuilder;
import org.spongycastle.openpgp.operator.bc.BcPGPContentSignerBuilder;
import org.spongycastle.openpgp.operator.bc.BcPGPDigestCalculatorProvider;
import org.spongycastle.openpgp.operator.bc.BcPGPKeyPair;
import org.spongycastle.openpgp.operator.bc.BcPublicKeyDataDecryptorFactory;
import org.spongycastle.openpgp.operator.jcajce.JcePGPDataEncryptorBuilder;
import org.spongycastle.openpgp.operator.jcajce.JcePublicKeyKeyEncryptionMethodGenerator;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.math.BigInteger;
import java.nio.charset.Charset;
import java.security.SecureRandom;
import java.util.Date;
import java.util.Iterator;
public class PgpUtils {
private static final String PROVIDER = "SC";
private static final String KEY_RING_ID = "[email protected]";
public static String decrypt(String encryptedText, String password) throws Exception {
byte[] encrypted = encryptedText.getBytes();
InputStream in = new ByteArrayInputStream(encrypted);
in = PGPUtil.getDecoderStream(in);
PGPObjectFactory pgpF = new PGPObjectFactory(in);
PGPEncryptedDataList enc;
Object o = pgpF.nextObject();
if (o instanceof PGPEncryptedDataList) {
enc = (PGPEncryptedDataList) o;
} else {
enc = (PGPEncryptedDataList) pgpF.nextObject();
}
PGPPrivateKey sKey = null;
PGPPublicKeyEncryptedData pbe = null;
while (sKey == null && enc.getEncryptedDataObjects().hasNext()) {
pbe = (PGPPublicKeyEncryptedData)enc.getEncryptedDataObjects().next();
sKey = getPrivateKey(getPGPSecretKeyRing(), pbe.getKeyID(), password.toCharArray());
}
if (pbe != null) {
InputStream clear = pbe.getDataStream(new BcPublicKeyDataDecryptorFactory(sKey));
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 new String(returnBytes);
}
return null;
}
private static PGPPublicKey getPublicKey(PGPPublicKeyRing publicKeyRing) {
Iterator<?> kIt = publicKeyRing.getPublicKeys();
while (kIt.hasNext()) {
PGPPublicKey k = (PGPPublicKey) kIt.next();
if (k.isEncryptionKey()) {
return k;
}
}
return null;
}
private static PGPPrivateKey getPrivateKey(PGPSecretKeyRing keyRing, long keyID, char[] pass) throws PGPException {
PGPSecretKey secretKey = keyRing.getSecretKey(keyID);
PBESecretKeyDecryptor decryptor = new BcPBESecretKeyDecryptorBuilder(new BcPGPDigestCalculatorProvider()).build(pass);
return secretKey.extractPrivateKey(decryptor);
}
public static String encrypt(String msgText) throws IOException, PGPException {
byte[] clearData = msgText.getBytes();
PGPPublicKey encKey = getPublicKey(getPGPPublicKeyRing());
ByteArrayOutputStream encOut = new ByteArrayOutputStream();
OutputStream out = new ArmoredOutputStream(encOut);
ByteArrayOutputStream bOut = new ByteArrayOutputStream();
PGPCompressedDataGenerator comData = new PGPCompressedDataGenerator(PGPCompressedDataGenerator.ZIP);
OutputStream cos = comData.open(bOut);
PGPLiteralDataGenerator lData = new PGPLiteralDataGenerator();
OutputStream pOut = lData.open(cos, PGPLiteralData.BINARY, PGPLiteralData.CONSOLE, clearData.length, new Date());
pOut.write(clearData);
lData.close();
comData.close();
PGPEncryptedDataGenerator encGen =
new PGPEncryptedDataGenerator(
new JcePGPDataEncryptorBuilder(PGPEncryptedData.AES_256).setWithIntegrityPacket(true).setSecureRandom(
new SecureRandom()).setProvider(PROVIDER));
if (encKey != null) {
encGen.addMethod(new JcePublicKeyKeyEncryptionMethodGenerator(encKey).setProvider(PROVIDER));
byte[] bytes = bOut.toByteArray();
OutputStream cOut = encGen.open(out, bytes.length);
cOut.write(bytes);
cOut.close();
}
out.close();
return new String(encOut.toByteArray());
}
public final static PGPKeyRingGenerator generateKeyRingGenerator (char[] pass) throws PGPException{
RSAKeyPairGenerator kpg = new RSAKeyPairGenerator();
kpg.init(new RSAKeyGenerationParameters(BigInteger.valueOf(0x10001), new SecureRandom(), 2048, 12));
PGPKeyPair rsakp_sign = new BcPGPKeyPair(PGPPublicKey.RSA_SIGN, kpg.generateKeyPair(), new Date());
PGPKeyPair rsakp_enc = new BcPGPKeyPair(PGPPublicKey.RSA_ENCRYPT, kpg.generateKeyPair(), new Date());
PGPSignatureSubpacketGenerator signhashgen = new PGPSignatureSubpacketGenerator();
signhashgen.setKeyFlags(false, KeyFlags.SIGN_DATA|KeyFlags.CERTIFY_OTHER|KeyFlags.SHARED);
signhashgen.setPreferredSymmetricAlgorithms(false, new int[]{SymmetricKeyAlgorithmTags.AES_256, SymmetricKeyAlgorithmTags.AES_192, SymmetricKeyAlgorithmTags.AES_128});
signhashgen.setPreferredHashAlgorithms(false, new int[]{HashAlgorithmTags.SHA256, HashAlgorithmTags.SHA1, HashAlgorithmTags.SHA384, HashAlgorithmTags.SHA512, HashAlgorithmTags.SHA224});
signhashgen.setFeature(false, Features.FEATURE_MODIFICATION_DETECTION);
PGPSignatureSubpacketGenerator enchashgen = new PGPSignatureSubpacketGenerator();
enchashgen.setKeyFlags(false, KeyFlags.ENCRYPT_COMMS | KeyFlags.ENCRYPT_STORAGE);
PGPDigestCalculator sha1Calc = new BcPGPDigestCalculatorProvider().get(HashAlgorithmTags.SHA1);
PGPDigestCalculator sha256Calc = new BcPGPDigestCalculatorProvider().get(HashAlgorithmTags.SHA256);
PBESecretKeyEncryptor pske = (new BcPBESecretKeyEncryptorBuilder(PGPEncryptedData.AES_256, sha256Calc, 0xc0)).build(pass);
PGPKeyRingGenerator keyRingGen = new PGPKeyRingGenerator (PGPSignature.POSITIVE_CERTIFICATION, rsakp_sign,
KEY_RING_ID, sha1Calc, signhashgen.generate(), null, new BcPGPContentSignerBuilder(rsakp_sign.getPublicKey().getAlgorithm(),
HashAlgorithmTags.SHA1), pske);
keyRingGen.addSubKey(rsakp_enc, enchashgen.generate(), null);
return keyRingGen;
}
private static PGPPublicKeyRing getPGPPublicKeyRing() throws IOException {
ArmoredInputStream ais = new ArmoredInputStream(new ByteArrayInputStream(Device.getDevice().getPgpPublicKey().getBytes()));
return (PGPPublicKeyRing) new PGPObjectFactory(ais).nextObject();
}
private static PGPSecretKeyRing getPGPSecretKeyRing() throws IOException {
ArmoredInputStream ais = new ArmoredInputStream(new ByteArrayInputStream(Device.getDevice().getPgpSecretKey().getBytes()));
return (PGPSecretKeyRing) new PGPObjectFactory(ais).nextObject();
}
public final static String genPGPPublicKey (PGPKeyRingGenerator krgen) throws IOException {
ByteArrayOutputStream baosPkr = new ByteArrayOutputStream();
PGPPublicKeyRing pkr = krgen.generatePublicKeyRing();
ArmoredOutputStream armoredStreamPkr = new ArmoredOutputStream(baosPkr);
pkr.encode(armoredStreamPkr);
armoredStreamPkr.close();
return new String(baosPkr.toByteArray(), Charset.defaultCharset());
}
public final static String genPGPPrivKey (PGPKeyRingGenerator krgen) throws IOException {
ByteArrayOutputStream baosPriv = new ByteArrayOutputStream ();
PGPSecretKeyRing skr = krgen.generateSecretKeyRing();
ArmoredOutputStream armoredStreamPriv = new ArmoredOutputStream(baosPriv);
skr.encode(armoredStreamPriv);
armoredStreamPriv.close();
return new String(baosPriv.toByteArray(), Charset.defaultCharset());
}
}
Here is how I create the private and public keys:
final PGPKeyRingGenerator krgen = PgpUtils.generateKeyRingGenerator("password".toCharArray());
String pgpPublicKey = PgpUtils.genPGPPublicKey(krgen);
String pgpSecretKey = PgpUtils.genPGPPrivKey(krgen);
And finally encrypting and decrypting using your own public key:
String encrypted = PgpUtils.encrypt("message text");
String decrypted = PgpUtils.decrypt(encrypted, "Password");