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Old 2020-02-21, 11:34 PM
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Join Date: Oct 2004
Location: Canada
Re: The Validity of MD5 Checksums

Tangerine Tree Verifying and Duplicating SHNs Quick Reference Guide (excerpt), 2003-05-29

here is another nice description of the problems with audio cdr trading in the 90s. complete guide amazingly still online with mkwACT tutorial and everything. of course we use st5 instead of md5 for audio files since 2005.
Quote:
Originally Posted by tdtree
Updated May 29th, 2003 12:38AM


What is SHN?

The purpose of the Shorten (SHN) format is not only to reduce the number of discs which have to be mailed or downloaded (6 instead of 10 for TT1, 8 instead of 14 for TT2), but more importantly to safeguard or "package" each music file in such a way that you can be 100% certain that what you have received is identical to the original.

People trust their standalone or computer-based CD-ROM or CD-RW drives to read and write CDs with no errors, especially at very high speeds. But I cannot count the number of times I have received CDs with pops, clicks, jumps, and entire sections missing due to errors in the reading or writing of CDs. For a time, there was a movement to ask everyone to record their CD-Rs slowly, at 4x or 2x, claiming that higher speeds were the cause of all the problems. Although reading and writing CDs at high speeds, especially on marginal equipment certainly does reduce the likelihood of producing perfect discs, speed alone is not the problem.

So what do we do? Do we all copy our CDs at 1x or 2x, sitting there for 40-80 minutes watching a progress indicator creep across the screen on our high-speed CD recorders that we blew $200 on? There is another solution.


First, the original (or close to it) CDs must be read into a computer with maximum accuracy. The concert trading community uses a music CD reading program called Exact Audio Copy which is explained further down this page.

Second, we "package" the audio into the SHN computer format. SHN is a lossless compression format, meaning that not one bit of sound quality is lost in the conversion. Think of it as "WinZip" for your music. Also, SHN packages contain an MD5 checksum which is a 'signature' that can be used to verify if the disc has been corrupted in any way.

Just having the music in a data rather than audio format lets us benefit from the fact that:
2-3% of an audio CD is used for error checking.
17% of a data CD is used for error checking.

Third, each person who receives an SHN disc or download should always confirm the integrity of the SHN files by comparing them to the MD5 checksum files before they start making copies or producing regular audio CDs from them.


I have heard people say "Maybe SHN is not ready for prime time?"

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