Nxt$Crypto.java

import java.io.UnsupportedEncodingException;
import java.security.MessageDigest;
import java.util.Arrays;

class Nxt$Crypto
{
  static byte[] getPublicKey(String secretPhrase)
  {
    try
    {
      byte[] publicKey = new byte[32];
      Nxt.Curve25519.keygen(publicKey, null, Nxt.getMessageDigest("SHA-256").digest(secretPhrase.getBytes("UTF-8")));
      
      return publicKey;
    }
    catch (RuntimeException|UnsupportedEncodingException e)
    {
      Nxt.logMessage("Error getting public key", e);
    }
    return null;
  }
  
  static byte[] sign(byte[] message, String secretPhrase)
  {
    try
    {
      byte[] P = new byte[32];
      byte[] s = new byte[32];
      MessageDigest digest = Nxt.getMessageDigest("SHA-256");
      Nxt.Curve25519.keygen(P, s, digest.digest(secretPhrase.getBytes("UTF-8")));
      
      byte[] m = digest.digest(message);
      
      digest.update(m);
      byte[] x = digest.digest(s);
      
      byte[] Y = new byte[32];
      Nxt.Curve25519.keygen(Y, null, x);
      
      digest.update(m);
      byte[] h = digest.digest(Y);
      
      byte[] v = new byte[32];
      Nxt.Curve25519.sign(v, h, x, s);
      
      byte[] signature = new byte[64];
      System.arraycopy(v, 0, signature, 0, 32);
      System.arraycopy(h, 0, signature, 32, 32);
      
      return signature;
    }
    catch (RuntimeException|UnsupportedEncodingException e)
    {
      Nxt.logMessage("Error in signing message", e);
    }
    return null;
  }
  
  static boolean verify(byte[] signature, byte[] message, byte[] publicKey)
  {
    try
    {
      byte[] Y = new byte[32];
      byte[] v = new byte[32];
      System.arraycopy(signature, 0, v, 0, 32);
      byte[] h = new byte[32];
      System.arraycopy(signature, 32, h, 0, 32);
      Nxt.Curve25519.verify(Y, v, h, publicKey);
      
      MessageDigest digest = Nxt.getMessageDigest("SHA-256");
      byte[] m = digest.digest(message);
      digest.update(m);
      byte[] h2 = digest.digest(Y);
      
      return Arrays.equals(h, h2);
    }