John wishes to install a new application onto his Windows 2000 server.

He wants to ensure that any application he uses has not been Trojaned.

What can he do to help ensure this?

A.
Compare the file’s MD5 signature with the one published on the distribution media

B.
Obtain the application via SSL

C.
Compare the file’s virus signature with the one published on the distribution media

D.
Obtain the application from a CD-ROM disc

Explanation:
MD5 was developed by Professor Ronald L. Rivest of MIT. What it does, to quote the executive summary of rfc1321, is:
[The MD5 algorithm] takes as input a message of arbitrary length and produces as output a 128- bit "fingerprint" or "message digest" of the input. It is conjectured that it is computationally infeasible to produce two messages having the same message digest, or to produce any message having a given prespecified target message digest. The MD5 algorithm is intended for digital signature applications, where a large file must be "compressed" in a secure manner before being

encrypted with a private (secret) key under a public-key cryptosystem such as RSA. In essence, MD5 is a way to verify data integrity, and is much more reliable than checksum and many other commonly used methods.