[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: draft-ietf-ipsec-ah-md5-00.txt




hugo@watson.ibm.com says:
> Just including the length as an authenticated field is NOT enough.
> To defeat the trivial appending attack on key-prepended MD5 one
> needs to specify that the length value appears in a FIXED OFFSET
> from the begining of the information being authenticated (e.g.,
> it is the first value in that information, or appears starting in
> byte 8, etc.).

It does. See rfc791 on IP. Total length always occupies the third and
fourth octet of the IP header.

Perry


References: