Re: Digital Watermarks for copy protection in recent Billbo

[tcmay@got.net (Timothy C. May)]

At 2:42 PM 7/23/96, Alex F wrote:
>> >  People buying CDs at a garage sale & getting arrested for
>> >piracy.  Wonderful.
>>
>> Arrests like this are uncommon. Even buying "cheap bikes" and other "cheap"
>> (= probably stolen and fenced) merchandise almost never subjects the
>> purchaser to criminal sanctions.
>
>Yes, but concievably if (whoever would be incharge, FBI?) *could*,
>under law do this, even if they are wrong.  It is a lot harder to
>prove that they intentionally harrassed *you* than it is for them to
>say that they were following leads and show evidence.  Yes, this may

To go to trial, an indictment would be needed. How likely is this? Not very.

Discussion of "in theory they could arrest you" points often neglects the
realities of the legal system.

A large fraction of pawnshop items have questionable provenance, the items
having been stolen at some time in the past. Could J. Random Buyer who
walks in, sees an item he likes, buys it, and walks out with it be
handcuffed and taken down the lockup for the crime of buying stolen
property? Doubtful, in the real world. And defense would be ridicuously
easy.


>Cds are often sampled at 48 these days.  Mine was, and we had to
>reduce it to 44.1 for mass producing (much to our surprise, since
>many CD manufacturers love getting stuff at 48 over 44.1)

A trivial increase in frequency, and still not allowing the hypothesized 30
KHz signal to be added. DATs often sample at 44 and 48 KHz, switchably. The
CD standard is of course still what it is.

>Not familiar with the Nyquist limit w/ regards to sampling rate vs
>frequency :(

Check any textbook, or even a good dictionary. Basically, it says that one
must sample at more than twice the frequency of the highest frequency to be
reconstructed. Thus, a 20 KHz top frequency needs at least 40 K samples per
second. The exact number is, I think, about 2.2x the freqency, which is why
CDs were standardized at 44 K samples per second per channel.

--Tim May

Boycott "Big Brother Inside" software!
We got computers, we're tapping phone lines, we know that that ain't allowed.
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Timothy C. May              | Crypto Anarchy: encryption, digital money,
tcmay@got.net  408-728-0152 | anonymous networks, digital pseudonyms, zero
W.A.S.T.E.: Corralitos, CA  | knowledge, reputations, information markets,
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