Welcome to my Homepage!portrait

May I introduce:

My name is Heinz Repp, and I live in Aurich, a small town in Ostfriesland in the northwestern corner of Germany. I am involved with computers since the mid seventies, a fact that may give you a hint about my age too.

My favorite operating system is OS/2, but alas, IBM has failed in adequately promoting it. Furthermore I use all variants of Windows and DOS too, and on very few occasions I get my old Atari ST out of the cellar <g>. Very long ago I started programming in BASIC, then tried Assembler (65xx, 680xx, 80x86), later Forth, then joined (Turbo-)Pascal, and now C. I am interested in AI, so I played a little with Prolog and (X)LISP. Oh, I nearly forgot: additionally I did a lot of database programming (xBase).

Cryptography has been one of my favorites since years. Long ago I coded my own version of the RSA algorithm in muMath, a symbolic language running under CP/M (oh dear). When I discovered PGP I liked it from the beginning. But the new encryption schemes introduced with version 5 (Diffie-Hellmann/Elgamal, DSS, CAST, 3DES) I could not get used to. RSA and IDEA are still the most efficient and - due to the long time of trying to break them without discovering severe weakness - most secure asymmetric and symmetric crypto systems. The only advantage the 'new' schemes offer is that they are (nearly) license-free, but they introduce incompatibility between different versions and platforms. Only the hash algorithm MD5 justified the replacement by SHA-1 by revealing significant weakness in recent examinations.

Don't get me wrong: CAST is nicely designed (3DES is a cripple - sacrificing performance to remedy poor security), the Diffie-Hellman-Algorithm is older than RSA and great for creating a shared secret (Elgamal uses it in a way it wasn't designed for), and the new AES (Rijndael) is going to become my new favourite; but I believe that compatibility is a precious gift, sacrificing it was unwise. I hope that the OpenPGP standard will provide for a new level of compatibility - and free programs like the Gnu Privacy Guard will spread it to many platforms.

Dealing with cryptography one day I had the idea to write a steganographic program, that hides secret information in a multimedia file. I learned the structures of picture and sound files and wrote the first version of Hide4PGP. The results were good with sound files and true color pictures, but very unsatisfactory with palette pictures (16 or 256 colors). So I brooded over it, tried some solutions, and out came a sophisticated palette opimization algorithm all by myself. The results were much better, but still outperformed by 'Spyder' (by Lucas Natraj and Philip Tellis). With their permission I further enhanced their algorithm, improved many other features, and out came Hide4PGP 2.0.

<p>The new version and some other programs by me are available here:</p> <ul> <li><a href="Hide4PGP.htm">Information about Hide4PGP (plus a tricky demo)</a></li> <li><a href="Hide4PGP.htm#downloads">Download Hide4PGP 2.0</a></li> <li><a href="HexMines.htm">HexMines 1.0 - a hexagonal Minesweeper clone</a><sup><img src="NEW.GIF" alt="neu!" border="0" height="12" width="31"></sup></li> <li><a href="DivSoft.htm">Other tiny programs written by me</a></li> <li><a href="HRKEYS.ASC"><img src="PGPKEYS.GIF" alt="keys" border="0" height="20" width="16" align="middle"> My PGP Keys (RSA preferred)</a></li> </ul> <p align="center"><a href="http://www.eff.org/BlueRibbon/"><img src="BLUERIBB.GIF" alt="Free Speech Online - Blue Ribbon Campaign" border="0" height="30" width="143"></a></p>

In real life I like sailing very much, nature in all its forms, travelling to foreign countries, sharing life with friends, music from classic to rock, reading books, playing guitar ...

<p>If you like, send me a message:</p> <div align="center"> <form action="mymail.html" method="GET"> <input type="image" src="MAIL.GIF"> </form> <br> <br> </div>