How to efficiently identify a binary file

Question

What\'s the most efficient way to identify a binary file? I would like to extract some kind of signature from a binary file and use it to compare it with others.

The bru

Answer 1

The usual answer is to use MD5, but I'd like to suggest that there are too many collisions to use MD5 in modern applications: http://www.mscs.dal.ca/~selinger/md5collision/

SHA-1 replaced MD5 over a decade ago.

NIST recommended in 2005 that SHA-2 should be used in place of SHA-1 by the year 2010, because of work that had been done to demonstrate collisions in reduced variants of SHA-1. (Which is pretty good foresight, since it is now known that it takes 2^51 work to find collisions in what should ideally require 2^80 work to find collisions.)

So please, based on what you're trying to do, and which other programs you may need to interoperate with, select among MD5 (please no), SHA-1 (I'd understand, but we can do better), and SHA-2 (pick me! pick me!).