Re: Checksums and best way to get'em
Re: Checksums and best way to get'em
- Subject: Re: Checksums and best way to get'em
- From: Nick Zitzmann <email@hidden>
- Date: Tue, 8 Jun 2004 07:30:44 -0600
On Jun 7, 2004, at 11:33 PM, April Gendill wrote:
But i'll try. How would one generate a checksum of a file and then
using that check sum verify whether or not changes have been made to
the file?
One other way of doing this is to use the MD5 or SHA-1 functions from
OpenSSL's libcrypto library. You can then read in the file using read()
or fread(), pass each byte through the "update" function, and get the
final digest from the "final" function. You can find out more by
running an apropos search for "md5" and "sha" on your computer if you
installed the BSD SDK when you installed Xcode.
If you do a checksum on a file, and it's different than the last time
the checksum was performed, then the file was changed. I assume you
know how to compare strings. Keep in mind that, if you're using these
functions to get the checksum of a prebound binary, then the checksum
will change when the binary is re-bound.
Nick Zitzmann
<
http://www.chronosnet.com/>
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