Cryptography Reference
In-Depth Information
package, that plugs into the parallel port
10.33
of a computer. Then the software
application sends an encrypted message to the dongle for verification before it
will run. Moreover, at selected points during its running, the application will
send messages to the dongle. If the dongle does not respond with the program's
validation code, the software ceases execution. In other words, the dongle must
remain plugged into the computer in order for the software to continue running.
Hence, although users may copy the program, they need a new dongle for each
copy, so must pay for each one. Modern dongles have a
pass-through
function
that allows a printer to be connected, for instance, thereby not tying up the
parallel port. Older versions were a nuisance since they did indeed tie up the
port and so were not very popular.
Most copyright infringements have been in the area of music downloaded
from the Internet. The majority of the recent major court battles and subse-
quent fights over piracy, copyright violations, and rights of users centered in this
arena.
MP3
: Most digital musicdownloaded from the Internet is in MP3 format.
In order to understand further the copyright/piracy issues, we must have some
understanding of this format and how it operates. Prior to the arrival of MP3 on
the digital scene, the format for downloading music from the Internet was
WAV
(pronounced “wave”, which stood for
waveform
audio), developed by Microsoft.
WAV files were monsters that could take vast amounts of storage space for a
CD, and take several hours to download it.
10.34
10.33
A parallel port (also called an LPT port), is an interface that supports transmission of
multiple bits at the same time for connecting an external device, which is usually a printer.
Most computers have both a parallel and a
serial
port. A serial port is slower than its
counterpart, since it is a general-purpose port in which 1 bit of information is transferred at
a time. Thus, it is usually employed for modems, mouses, and some communications devices.
Most serial ports use an RS-232C type connector, so are often called RS-232 ports. In the past,
serial ports were used to transfer images from digital cameras, but this was painfully slow. It
is being replaced by the much faster USB ports on both digital cameras and computers.
USB
means
Universal Serial Bus
, an external bus standard, which supports data transfer rates of
12Mbps. (Think of a
bus
as a transmission pathway.) USB ports allow one to “daisy-chain”
devices, that is connect one device to another. In fact, a single USB port can be used to
connect up to 127 peripherals. This means that a new device may be added to a computer
without the necessity of adding an adapter card. The port looks like a vertically positioned
slim rectangle, typically on the back of a computer or monitor. The widespread use of the
USB port really began with the popularity of Apple's iMAC, released in 1998. It is now
expected that all serial and parallel ports will eventually be replaced by USB ports. The USB
specification was published in 1996 by a consortium of corporations led by Intel Corporation.
10.34
To understand why, we must learn something about CDs. Digital audio for CDs is ob-
tained by using two-byte numbers to represent samples of the original analog signal. CD
sampling
is akin to frames of a motion picture, but with audio the “samples” are taken at a
rate of 44.1 kHz (44,100 times per second), and this is naturally done in stereo (two channels).
Therefore, one minute of CD audio contains 60
×
2
×
44
,
100
×
2=10
,
584
,
000 bytes. Since
an average song is three minutes long, then we are talking about roughly 30 MB. (Since we
get into such large numbers in these discussions, it is convenient to talk in terms of
megabytes
(MB), where 1
MB
=1
,
048
,
576 bytes or 1024 kilobytes (KB), where 1
KB
= 1024 bytes.)
Supposing that an Internet connection has the (not unreasonable cable-type) rate of about
60 seconds to download 1 MB, then one song will take about 30 minutes, and a complete CD
with say a dozen songs on it will take six hours to download!
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