Hash collisions

Hi all,

I am working through some past questions for a mid term exam:

"Assuming that it is computationally infeasible to launch attacks that
require 2^128 computations of hash values, how long should the hash
values be to achieve weak and strong collision resistance
respectively?" - 5 marks.

I've done some research on the internet, and can't find any hard
definitions for "strong" or "weak" collision resistance. Obviously
collisions are impossible to avoid completely (unless of course the
hash is larger than the messages themselves!).

But do you have any idea how to arrive at hard and fast numbers for
these terms?

Thanks,

Mike
.

Relevant Pages

  • Re: Insecure Hash Algorithms (MD5) and NTLMv2
    ... hash when you have no access to the original input. ... The only weakness that's really in the air is Collision Resistance, ... Audit your website security with Acunetix Web Vulnerability Scanner: ... Cross site scripting and other web attacks before hackers do! ...
    (Pen-Test)
  • Re: Reverse usage of public/private RSA encryption keys for licensing?
    ... It's just that there is a theorem that proves that if we use random oracle ... algorithm to forge signature (RSA private key encryption of random oracle ... hash) gives ability to solve RSA problem with sufficient amount of signing ... SHA1 doesn't provide the same level of collision resistance, ...
    (microsoft.public.dotnet.framework)
  • Re: Reverse usage of public/private RSA encryption keys for licensing?
    ... It's just that there is a theorem that proves that if we use random oracle ... algorithm to forge signature (RSA private key encryption of random oracle ... hash) gives ability to solve RSA problem with sufficient amount of signing ... SHA1 doesn't provide the same level of collision resistance, ...
    (microsoft.public.dotnet.security)
  • Re: Regarding sudo
    ... As a result the search space is reduced slightly. ... So we have bajillions of diferent passwords all given the same hash? ... Collision resistance is described in the above article as weak or strong, ...
    (comp.os.linux.setup)