Response to MPA Threat Letter

						Computer Science Department
						Carnegie Mellon University
						Pittsburgh, PA 15213-3891

						February 6, 2001

Mr. Hemanshu Nigam
Director, Worldwide Internet Enforcement
Motion Picture Association
15503 Ventura Boulevard
Encino, CA  91436

Dear Mr. Nigam:

I write in response to your email of yesterday, in which you allege
that I am illegally providing a "circumvention device" as defined in
17 USC 1201(a)(2).  The only URL given in your complaint was

which is the address of my personal home page.  I understand that you
are not objecting to my entire home page, but rather, to certain
portions of it that deal with DeCSS.  However, you neglected to
specify the files that you object to.  If you visit my "Gallery of CSS
Descramblers" at

you will find the DeCSS code in several dozen forms.  The C source
code is there, naturally.  But the same ideas are also expressed in
many other forms, including:
  translations of the algorithm into Scheme, and Standard ML of New Jersey

  translation into a C-like language that is not C (and for which no
	compiler currently exists, so the file is not compilable)

  a line-by-line translation of the C code into English, done by myself

  a line-by-line English translation, in which the original C source
	code has been interspersed with the equivalent English statements

  a translation of the C code into English, done automatically by a Perl
	program, along with another Perl program that can translate the
	English back into C automatically

  a perfectly legible PICTURE of the C source code (three GIF files)

  a photograph of a t-shirt on which the C source code is printed

  an audio recording of a person reading the English version of the 
	source code aloud

  an audio recording of a person singing the source code, with
	guitar and drum accompaniment

There are numerous other forms as well, which you can see for yourself
if you visit the Gallery.  In addition, there is a section devoted to
the cryptographic research of Frank Stevenson, including essays and
several small C programs Mr. Stevenson wrote that illustrate his
ideas.  You can find a listing of the various files here:

In order for me to consider the allegation you raised in your letter,
I request that you specify the URL for each of the files on my web
site to which you are objecting, and for each such file, give the legal
basis for your objection.  It would also be helpful if you would
explain, for those representations of the DeCSS algorithm to which you
do not object (such as, perhaps, the recording of someone singing the
source code), why you do not object to my publishing the algorithm in
that particular form.

Finally, I think I should mention that the Gallery of CSS Descramblers
is by now a well-known academic work.  You will find on the main
Gallery page two dozen press clippings of articles that mention the
Gallery or my testimony about it as an expert witness in the New York
trial you referred to in your letter.  The Gallery is linked to from
many sources, including the Electronic Frontier Foundation and USA
Today.  It is listed on my curriculum vitae, and in my online list of
scholarly works at

I would like to know if it is the intent of the MPA to exert editorial
control over scholarly publications by computer science faculty that
deal with DeCSS, and if so, exactly which sort of publications will
the MPA permit in the future, and which sort will result in legal
threats such as your letter of yesterday.

Thank you for your time.


Dr. David S. Touretzky
Principal Scientist