PKI Guide

This document offers a practical introduction to Public Key Infrastructures and the fundamental technologies which are involved. After a formal outline of PKI, two popular implementations are discussed: X.509 PKI and OpenPGP PKI. Every aspect and every task is demonstrated using commands that are based either on the OpenSSL library or the GnuPG command line tool.

How TermSrvCopyKeyOnce Influences Shadow Keys

Windows Server with Terminal Services usually runs in execute mode to serve applications. Whenever a new application is being installed, this must be done in install mode for Windows to monitor write operations affecting HKEY_CURRENT_USER. Switching between install and execute mode is performed by change user as described in MS KB 186504 - Terminal Server Commands: CHANGE. All changes to HKEY_CURRENT_USER are then shadowed to HKEY_LOCAL_MACHINE\Software\Microsoft\Windows NT\CurrentVersion\Terminal Server\Install, hence the name shadow keys. These keys are copied to a user’s HKEY_CURRENT_USER hive during logon.

Welcome to My Blog

I proudly present my blog and … no content, yet. I am currently preparing the first article to be published in the course of the next few days, so stay tuned. In the meantime please subscribe to the RSS feed ;-)

Perl Performance Considerations

As stated earlier in avoiding regular expressions, it may beneficial to avoid regexes to improve performance. The following code demonstrates five different ways to split a string.

My Perl Library

The modules collected herein provide perl classes which I base further projects on.

My Perl Math Module

This perl module contains several useful functions for the statistical analysis of a series of measurements. These were implemented during my diploma thesis to.

XML Processing in Perl

Use the following modules to process XML in Perl:


The ssh-add utility (see SSH agent for details) accepts a program in the environment variable SSH_ASKPASS that retrieves a passphrase from the user. This is especially useful to use the SSH agent from a script or a GUI (i.e. without a console).

Server Configuration

The following list will provide some hints how to configure you SSH daemon although most options will not have to be modified as they also contain reasonable defaults.

Perl Prototype

The following code forms the typical header for my Perl scripts: