code: public static String hash(char[] password, int cost)
  	{
  		String salt = BCryptImpl.gensalt(cost);
  
  		return BCryptImpl.hashpw(new String(password), salt);
  	}
docs: @param password
  the plaintext password
  @param cost
  the computation cost (complexity increases at <code>2**cost</code>)
  
  @return