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/**
* Copyright (C) 2013 Open Whisper Systems
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
package org.whispersystems.libaxolotl.ecc;
import org.whispersystems.libaxolotl.InvalidKeyException;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;
public class Curve25519 {
static {
System.loadLibrary("curve25519");
try {
random = SecureRandom.getInstance("SHA1PRNG");
} catch (NoSuchAlgorithmException e) {
throw new AssertionError(e);
}
}
private static final SecureRandom random;
private static native byte[] calculateAgreement(byte[] ourPrivate, byte[] theirPublic);
private static native byte[] generatePublicKey(byte[] privateKey);
private static native byte[] generatePrivateKey(byte[] random);
private static native byte[] calculateSignature(byte[] random, byte[] privateKey, byte[] message);
private static native boolean verifySignature(byte[] publicKey, byte[] message, byte[] signature);
public static ECKeyPair generateKeyPair() {
byte[] privateKey = generatePrivateKey();
byte[] publicKey = generatePublicKey(privateKey);
return new ECKeyPair(new DjbECPublicKey(publicKey), new DjbECPrivateKey(privateKey));
}
static byte[] calculateAgreement(ECPublicKey publicKey, ECPrivateKey privateKey) {
return calculateAgreement(((DjbECPrivateKey)privateKey).getPrivateKey(),
((DjbECPublicKey)publicKey).getPublicKey());
}
static byte[] calculateSignature(ECPrivateKey privateKey, byte[] message) {
byte[] random = getRandom(64);
return calculateSignature(random, ((DjbECPrivateKey)privateKey).getPrivateKey(), message);
}
static boolean verifySignature(ECPublicKey publicKey, byte[] message, byte[] signature) {
return verifySignature(((DjbECPublicKey)publicKey).getPublicKey(), message, signature);
}
static ECPublicKey decodePoint(byte[] encoded, int offset)
throws InvalidKeyException
{
int type = encoded[offset] & 0xFF;
byte[] keyBytes = new byte[32];
System.arraycopy(encoded, offset+1, keyBytes, 0, keyBytes.length);
if (type != Curve.DJB_TYPE) {
throw new InvalidKeyException("Bad key type: " + type);
}
return new DjbECPublicKey(keyBytes);
}
private static byte[] generatePrivateKey() {
byte[] privateKey = new byte[32];
random.nextBytes(privateKey);
return generatePrivateKey(privateKey);
}
private static byte[] getRandom(int size) {
try {
byte[] random = new byte[size];
SecureRandom.getInstance("SHA1PRNG").nextBytes(random);
return random;
} catch (NoSuchAlgorithmException e) {
throw new AssertionError(e);
}
}
}
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