Re: MD5 check sum of a file
Re: MD5 check sum of a file
- Subject: Re: MD5 check sum of a file
- From: Nicko van Someren <email@hidden>
- Date: Thu, 14 Feb 2008 13:03:55 +0000
On 13 Feb 2008, at 15:58, Jens Alfke wrote:
On 13 Feb '08, at 2:49 AM, <email@hidden> <email@hidden
> wrote:
I want to find out the md5 check sum of a file while giving the
path of
the file.
#include <CommonCrypto/CommonDigest.h>
This is Apple's preferred high-level API for generating digests/
hashes.
Is either the fact that this is preferred, or the header itself,
documented anywhere? Typing either "CommonCrypto" or "CommonDigest"
into the full text search no the latest Xcode yields just one hit in
some example code and no documentation whatsoever.
If you have a choice of algorithms, and if this involves security at
all, SHA-1 is a better choice. There are known weaknesses in MD5.
There are known weaknesses in SHA-1 as well (both have viable
collision attacks, neither has a viable second pre-image attack). If
the hash is being used for security then SHA-256 (in the same header
file) would be even better. That said, if all you are doing is
checking that bits didn't get corrupted in transit then MD5 is
probably just fine.
Cheers,
Nicko
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