Replaying and server side caching.

Jacques A. Vidrine n+krb at
Fri Apr 11 13:21:44 EDT 2003

On Fri, Apr 11, 2003 at 09:41:22AM -0700, Nicolas Williams wrote:
> Though I suppose that it might be easier to mount a dictionary attack
> against an AS-REP's enc-part than against a pa-enc-timestamp.  Is it?

No.  They are both quite easy due to ASN.1 encoding regularities.
In the first 16 bytes of either, much of the content is known or
trivially recognizable.  The PA-ENC-TIMESTAMP content is mostly known
except for perhaps the hour/minute/seconds part.  For example,

  x30 x0E xA0 x11 x18 x0F "20030411HHMMSSZ"

(with the slight wrinkle that there may be a pausec member that changes
the value of the 2nd octet).

Actual DER maybe be slightly different from the above due to sloppy
work on my part :-) but you see what I mean.

Jacques A. Vidrine <nectar at>
NTT/Verio SME          .     FreeBSD UNIX     .       Heimdal Kerberos
jvidrine at     .  nectar at  .          nectar at

More information about the krbdev mailing list