How can I increase memory security in Delphi?

Question

Is it possible to \"wipe\" strings in Delphi? Let me explain:

I am writing an application that will include a DLL to authorise users. It will read an encrypted file

Answer 1

Two general points about this:

First, this is one of those areas where "if you have to ask, you probably shouldn't be doing this." And please don't take that the wrong way; I mean no disrespect to your programming skills. It's just that writing secure, cryptographically strong software is something that either you're an expert at or you aren't. Very much in the same way that knowing "a little bit of karate" is much more dangerous than knowing no karate at all. There are a number of third-party tools for writing secure software in Delphi which have expert support available; I would strongly encourage anyone without a deep knowledge of cryptographic services in Windows, the mathematical foundations of cryptography, and experience in defeating side channel attacks to use them instead of attempting to "roll their own."

To answer your specific question: The Windows API has a number of functions which are helpful, such as CryptProtectMemory. However, this will bring a false sense of security if you encrypt your memory, but have a hole elsewhere in the system, or expose a side channel. It can be like putting a lock on your door but leaving the window open.