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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.curve25519.Curve25519KeyPair;
import org.whispersystems.libaxolotl.InvalidKeyException;
import org.whispersystems.curve25519.Curve25519;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;
public class Curve {
public static final int DJB_TYPE = 0x05;
public static boolean isNative() {
return Curve25519.isNative();
}
public static ECKeyPair generateKeyPair() {
SecureRandom secureRandom = getSecureRandom();
Curve25519KeyPair keyPair = Curve25519.generateKeyPair(secureRandom);
return new ECKeyPair(new DjbECPublicKey(keyPair.getPublicKey()),
new DjbECPrivateKey(keyPair.getPrivateKey()));
}
public static ECPublicKey decodePoint(byte[] bytes, int offset)
throws InvalidKeyException
{
int type = bytes[offset] & 0xFF;
switch (type) {
case Curve.DJB_TYPE:
byte[] keyBytes = new byte[32];
System.arraycopy(bytes, offset+1, keyBytes, 0, keyBytes.length);
return new DjbECPublicKey(keyBytes);
default:
throw new InvalidKeyException("Bad key type: " + type);
}
}
public static ECPrivateKey decodePrivatePoint(byte[] bytes) {
return new DjbECPrivateKey(bytes);
}
public static byte[] calculateAgreement(ECPublicKey publicKey, ECPrivateKey privateKey)
throws InvalidKeyException
{
if (publicKey.getType() != privateKey.getType()) {
throw new InvalidKeyException("Public and private keys must be of the same type!");
}
if (publicKey.getType() == DJB_TYPE) {
return Curve25519.calculateAgreement(((DjbECPublicKey)publicKey).getPublicKey(),
((DjbECPrivateKey)privateKey).getPrivateKey());
} else {
throw new InvalidKeyException("Unknown type: " + publicKey.getType());
}
}
public static boolean verifySignature(ECPublicKey signingKey, byte[] message, byte[] signature)
throws InvalidKeyException
{
if (signingKey.getType() == DJB_TYPE) {
return Curve25519.verifySignature(((DjbECPublicKey)signingKey).getPublicKey(), message, signature);
} else {
throw new InvalidKeyException("Unknown type: " + signingKey.getType());
}
}
public static byte[] calculateSignature(ECPrivateKey signingKey, byte[] message)
throws InvalidKeyException
{
if (signingKey.getType() == DJB_TYPE) {
return Curve25519.calculateSignature(getSecureRandom(), ((DjbECPrivateKey)signingKey).getPrivateKey(), message);
} else {
throw new InvalidKeyException("Unknown type: " + signingKey.getType());
}
}
private static SecureRandom getSecureRandom() {
try {
return SecureRandom.getInstance("SHA1PRNG");
} catch (NoSuchAlgorithmException e) {
throw new AssertionError(e);
}
}
}
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