I need to find a utility that will wrap a file in a CRC algorithm.  I
have an excel spreadsheet with navigation data that I want to send to
another person.  To ensure that the file arrives intact I want to run
it through a CRC hash algorithm.  CRC stands for "cyclical redundancy
checking".  To be complete your answer must direct me to a utility
that will wrap an excel table of data in a CRC.

---

Request for Question Clarification by leapinglizard-ga on 13 May 2006 09:31 PDT

CRC is not a hash algorithm, but a way to add redundant information to
data so that errors can be automatically corrected to a certain point.
If all you want is a way to ensure that your file has been transmitted
properly, it suffices to get a hash value for the file, which your
correspondent can check at the other end. If I show you how to do this
with a readily available hash utility, will you accept it as an
answer?

leapinglizard

---

Request for Question Clarification by leapinglizard-ga on 13 May 2006 09:39 PDT

Actually, CRC does not allow for error correction, but only error
detection. Its mathematical properties make it useful for detecting
errors in a continuous stream of data. To detect errors in a discrete
chunk of data, hashing is the usual approach. In any case, what I can
offer is a standard method for your correspondent to use a hash
utility to verify that the Excel spreadsheet has been transmitted
without any data corruption.

leapinglizard

Dear ottawaelmer,


The ZIP archive format uses CRC to guard against data corruption.

    One of the most commonly encountered CRC algorithms is known
    as CRC-32, used by (among others) Ethernet, FDDI, ZIP and other
    archive formats, and PNG image format.

Wikipedia: Cyclic redundancy check: Implementation
http://en.wikipedia.org/wiki/Cyclic_redundancy_check#Implementation


Therefore, you can employ CRC on your spreadsheet by making a ZIP archive
from the Excel file using a free utility such as ZipCentral.

PC World: Downloads: ZipCentral
http://www.pcworld.com/downloads/file_description/0,fid,6531,00.asp

Once your correspondent has installed ZipCentral, he can open the ZIP
archive and extract the Excel file. ZipCentral will issue a warning
if it detects error corruption based on the CRC-32 algorithm. Your
correspondent can also run CRC-32 manually by using the "Test" button
at the far right of ZipCentral's toolbar.


An alternative is for your correspondent to run a standalone CRC utility,
such as CRCheck32, on the ZIP archive you have made from the spreadsheet
file.

Breezin Software: CRCheck32
http://www.breezin.net/sdetails.php?SID=2http://www34.brinkster.com/dizzyk/crc32.asp


Finally, it is possible to calculate the CRC-32 value of a file without
making a ZIP archive from it. The CheckCRC.exe program in the following
package will calculate CRC-32 for the Excel spreadsheet at your end,
which your correspondent can verify by running CheckCRC.exe on his copy
of the file. If you and your correspondent don't get the same result,
the file has been corrupted.

Brinkster: CRC32: CheckCRC.zip
http://www34.brinkster.com/dizzyk/download/CheckCRC.zip


I have enjoyed answering your question. If you have any concerns about
the accuracy or completeness of my research, please advise me through
a Clarification Request and allow me the opportunity to fully meet your
needs before you rate this answer.

Regards,

leapinglizard


Search strategy:

crc error detect
://www.google.com/search?q=crc+error+detect&start=0&ie=utf-8&oe=utf-8&client=firefox-a&rls=org.mozilla:en-US:official

crc32 calculator
://www.google.com/search?hl=en&hs=v6K&client=firefox-a&rls=org.mozilla:en-US:official&sa=X&oi=spell&resnum=0&ct=result&cd=1&q=crc32+calculator&spell=1

There are many hash algorithms. CRC is one of them. It happens to have
some very nice mathematical properties, is good at detecting common
transmission errors, and is easy to compute.

Your answer looks to be complete.  Thanks for your prompt reply.  I'll
post a rating in a couple of days.  Thanks again.