Recent MAC improvements: Test Results

Daniel Kahn Gillmor at
Tue Jun 12 09:35:58 EST 2007

Hash: SHA1

On Mon 2007-06-11 18:46:49 -0400, Chris Rapier wrote:

> I ran it a few times earlier with aes128 but the results were 
> inconsistent. I felt it was because I was hitting a disk i/o bottleneck 
> instead of a processor limitation. I'll try it now with arcfour256.

if you're worried that it's a disk I/O bottleneck, you could try
sourcing from /dev/zero (by analogy with your current sinking to
/dev/null).  That would take the disks out of the picture entirely.

Alternately, you could use dd to create a huge sparse file that
doesn't use any room on the disk.  For example, a 1G file that only
uses 1K on disk:

[0 dkg at squeak ~]$ dd if=/dev/zero bs=1K count=1 seek=1M of=bigfile
1+0 records in
1+0 records out
1024 bytes (1.0 kB) copied, 0.000249195 seconds, 4.1 MB/s
[0 dkg at squeak ~]$ ls -la bigfile 
- -rw-r--r-- 1 dkg dkg 1073742848 2007-06-11 19:33 bigfile
[0 dkg at squeak ~]$ 

If it turns out that the MAC algorithms you're testing work
differently when the cleartext stream is all the same byte, this won't
work, of course.

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