How many keys does Triple DES encryption need?
<p>I am porting some C# code to C++, and trying to encrypt a textfile with Triple DES encryption. But I am confused; some encryption APIs only require one key for Triple DES (C# for example: <a href="https://stackoverflow.com/questions/11413576/how-to-implement-triple-des-in-c-sharp-complete-example">How to implement Triple DES in C# (complete example)</a> ), while others require 2 or 3 keys (in several C++ implementations I've found). </p>

<p>Why is that?</p>