RE: MD5 x SHA-1

["Bill Royds" <broyds () rogers com>]

I once did a comparison of MD5 versus SHA1 when generating checksums of binaries before backing them up.
Our policy was to calculate a cryptographic checksum has of every file in backup, put that on backup tape, then the 
backup ufsdump. Saved our bacon several times when we could trace back to exactly when a file was corrupted.

MD5 is about 50% faster than SHA1, but as others have said SHA1 is considered more secure.
Basically there is a greater chance of an attacker being able to add nonce bytes to a modified file to get same hash 
with MD5 than SHA1 (SHA1 uses more widely distributed bytes to generate the hash). 
  But the modifications that allow one to spoof the hash are generally computationally difficult to calculate and 
modify the file in other obvious ways (file size, in particular).

-----Original Message-----
From: firewall-wizards-admin () honor icsalabs com
[mailto:firewall-wizards-admin () honor icsalabs com]On Behalf Of Brian A
Kee
Sent: Sat December 07 2002 06:45
To: firewall-wizards () honor icsalabs com
Subject: RE: [fw-wiz] MD5 x SHA-1


In my experience better is relative.

I will assume that you are meaning which is more secure.

Everything that I have read states that SHA-1 is the more secure hashing
algorythm. They also state that there is a performance cost associated with
this algorythm compared to MD5.

I have never really taken the time actually test what the performance cost
difference is, nor whether or not the algorythm is actually more secure.

This information can be found in various textbooks including Applied
Crytpography. I beleive that this is referenced in many vendor IPSEC
configurration guides.

In my experience, both seem to be as good an the other. I have configured
many a VPN where I have chosen either algorythm. I have been equally happy
with both applications.

TM

-----Original Message-----
From: firewall-wizards-admin () honor icsalabs com
[mailto:firewall-wizards-admin () honor icsalabs com]On Behalf Of Roberto
Joao Lopes Garcia
Sent: Friday, December 06, 2002 12:06 PM
To: firewall-wizards () honor icsalabs com
Subject: [fw-wiz] MD5 x SHA-1


Hi

I need to know  which is better as a file hash, that is, to see if a file
was modified

MD5 or SHA-1


Can some one, please, point me to some information

Thank you

Roberto

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