Minor update of German minihowto

[Michael.Fischer.von.Mollard]

The subject says it all: there is a minor update of my mini Howto. Thanks
to Werner Koch for his hints. Big corrections were not necessary, so the
main news are smaller clarifications and a new section ´limits of
encryption´ which talks about other possible attacks on privacy. 

	MfG
	  MFvM

Michael Fischer v. Mollard
fischer at math.uni-goettingen.de