content: /**
   * Copyright (C) 2013-2016 Open Whisper Systems
   *
   * Licensed according to the LICENSE file in this repository.
   */
  package org.whispersystems.libsignal.ecc;
  
  import org.whispersystems.curve25519.Curve25519;
  import org.whispersystems.curve25519.Curve25519KeyPair;
  import org.whispersystems.curve25519.VrfSignatureVerificationFailedException;
  import org.whispersystems.libsignal.InvalidKeyException;
  
  import static org.whispersystems.curve25519.Curve25519.BEST;
  
  public class Curve {
  
    public  static final int DJB_TYPE   = 0x05;
  
    public static boolean isNative() {
      return Curve25519.getInstance(BEST).isNative();
    }
  
    public static ECKeyPair generateKeyPair() {
      Curve25519KeyPair keyPair = Curve25519.getInstance(BEST).generateKeyPair();
  
      return new ECKeyPair(new DjbECPublicKey(keyPair.getPublicKey()),
                           new DjbECPrivateKey(keyPair.getPrivateKey()));
    }
  
    public static ECPublicKey decodePoint(byte[] bytes, int offset)
        throws InvalidKeyException
    {
      if (bytes == null || bytes.length - offset < 1) {
        throw new InvalidKeyException("No key type identifier");
      }
  
      int type = bytes[offset] & 0xFF;
  
      switch (type) {
        case Curve.DJB_TYPE:
          if (bytes.length - offset < 33) {
            throw new InvalidKeyException("Bad key length: " + bytes.length);
          }
  
          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 == null) {
        throw new InvalidKeyException("public value is null");
      }
  
      if (privateKey == null) {
        throw new InvalidKeyException("private value is null");
      }
  
      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.getInstance(BEST)
                         .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 == null || message == null || signature == null) {
        throw new InvalidKeyException("Values must not be null");
      }
  
      if (signingKey.getType() == DJB_TYPE) {
        return Curve25519.getInstance(BEST)
                         .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 == null || message == null) {
        throw new InvalidKeyException("Values must not be null");
      }
  
      if (signingKey.getType() == DJB_TYPE) {
        return Curve25519.getInstance(BEST)
                         .calculateSignature(((DjbECPrivateKey) signingKey).getPrivateKey(), message);
      } else {
        throw new InvalidKeyException("Unknown type: " + signingKey.getType());
      }
    }
  
    public static byte[] calculateVrfSignature(ECPrivateKey signingKey, byte[] message)
        throws InvalidKeyException
    {
      if (signingKey == null || message == null) {
        throw new InvalidKeyException("Values must not be null");
      }
  
      if (signingKey.getType() == DJB_TYPE) {
        return Curve25519.getInstance(BEST)
                         .calculateVrfSignature(((DjbECPrivateKey)signingKey).getPrivateKey(), message);
      } else {
        throw new InvalidKeyException("Unknown type: " + signingKey.getType());
      }
    }
  
    public static byte[] verifyVrfSignature(ECPublicKey signingKey, byte[] message, byte[] signature)
        throws InvalidKeyException, VrfSignatureVerificationFailedException
    {
      if (signingKey == null || message == null || signature == null) {
        throw new InvalidKeyException("Values must not be null");
      }
  
      if (signingKey.getType() == DJB_TYPE) {
        return Curve25519.getInstance(BEST)
                         .verifyVrfSignature(((DjbECPublicKey) signingKey).getPublicKey(), message, signature);
      } else {
        throw new InvalidKeyException("Unknown type: " + signingKey.getType());
      }
    }
  
  }
  