public static String hash(byte[] m){
		MessageDigest md = null;
	    byte[] hashed = null;
		try {
	        md = MessageDigest.getInstance("SHA-256");
	    }
	    catch(NoSuchAlgorithmException e) {
	        e.printStackTrace();
	    }
		hashed = md.digest(m);
	    return byteToHex(hashed);
	}