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package org.whispersystems.libaxolotl.util;
import org.whispersystems.libaxolotl.IdentityKey;
import org.whispersystems.libaxolotl.IdentityKeyPair;
import org.whispersystems.libaxolotl.InvalidKeyException;
import org.whispersystems.libaxolotl.ecc.Curve;
import org.whispersystems.libaxolotl.ecc.ECKeyPair;
import org.whispersystems.libaxolotl.state.PreKeyRecord;
import org.whispersystems.libaxolotl.state.SignedPreKeyRecord;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;
import java.util.LinkedList;
import java.util.List;
/**
* Helper class for generating keys of different types.
*
* @author Moxie Marlinspike
*/
public class KeyHelper {
private KeyHelper() {}
/**
* Generate an identity key pair. Clients should only do this once,
* at install time.
*
* @return the generated IdentityKeyPair.
*/
public static IdentityKeyPair generateIdentityKeyPair() {
ECKeyPair keyPair = Curve.generateKeyPair();
IdentityKey publicKey = new IdentityKey(keyPair.getPublicKey());
return new IdentityKeyPair(publicKey, keyPair.getPrivateKey());
}
/**
* Generate a registration ID. Clients should only do this once,
* at install time.
*
* @param extendedRange By default (false), the generated registration
* ID is sized to require the minimal possible protobuf
* encoding overhead. Specify true if the caller needs
* the full range of MAX_INT at the cost of slightly
* higher encoding overhead.
* @return the generated registration ID.
*/
public static int generateRegistrationId(boolean extendedRange) {
try {
SecureRandom secureRandom = SecureRandom.getInstance("SHA1PRNG");
if (extendedRange) return secureRandom.nextInt(Integer.MAX_VALUE - 1) + 1;
else return secureRandom.nextInt(16380) + 1;
} catch (NoSuchAlgorithmException e) {
throw new AssertionError(e);
}
}
public static int getRandomSequence(int max) {
try {
return SecureRandom.getInstance("SHA1PRNG").nextInt(max);
} catch (NoSuchAlgorithmException e) {
throw new AssertionError(e);
}
}
/**
* Generate a list of PreKeys. Clients should do this at install time, and
* subsequently any time the list of PreKeys stored on the server runs low.
* <p>
* PreKey IDs are shorts, so they will eventually be repeated. Clients should
* store PreKeys in a circular buffer, so that they are repeated as infrequently
* as possible.
*
* @param start The starting PreKey ID, inclusive.
* @param count The number of PreKeys to generate.
* @return the list of generated PreKeyRecords.
*/
public static List<PreKeyRecord> generatePreKeys(int start, int count) {
List<PreKeyRecord> results = new LinkedList<>();
start--;
for (int i=0;i<count;i++) {
results.add(new PreKeyRecord(((start + i) % (Medium.MAX_VALUE-1)) + 1, Curve.generateKeyPair()));
}
return results;
}
/**
* Generate the last resort PreKey. Clients should do this only once, at install
* time, and durably store it for the length of the install.
*
* @return the generated last resort PreKeyRecord.
*/
public static PreKeyRecord generateLastResortPreKey() {
ECKeyPair keyPair = Curve.generateKeyPair();
return new PreKeyRecord(Medium.MAX_VALUE, keyPair);
}
/**
* Generate a signed PreKey
*
* @param identityKeyPair The local client's identity key pair.
* @param signedPreKeyId The PreKey id to assign the generated signed PreKey
*
* @return the generated signed PreKey
* @throws InvalidKeyException when the provided identity key is invalid
*/
public static SignedPreKeyRecord generateSignedPreKey(IdentityKeyPair identityKeyPair, int signedPreKeyId)
throws InvalidKeyException
{
ECKeyPair keyPair = Curve.generateKeyPair();
byte[] signature = Curve.calculateSignature(identityKeyPair.getPrivateKey(), keyPair.getPublicKey().serialize());
return new SignedPreKeyRecord(signedPreKeyId, System.currentTimeMillis(), keyPair, signature);
}
public static ECKeyPair generateSenderSigningKey() {
return Curve.generateKeyPair();
}
public static byte[] generateSenderKey() {
try {
byte[] key = new byte[32];
SecureRandom.getInstance("SHA1PRNG").nextBytes(key);
return key;
} catch (NoSuchAlgorithmException e) {
throw new AssertionError(e);
}
}
public static int generateSenderKeyId() {
try {
return SecureRandom.getInstance("SHA1PRNG").nextInt(Integer.MAX_VALUE);
} catch (NoSuchAlgorithmException e) {
throw new AssertionError(e);
}
}
}
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