How to .zip a file?

[Adam_Bell]

Glad it worked. MD5 is a neat way to check.

[Mark67]

I don’t understand the hexadecimal value returned so I’ll just take your word to that until I have the time to dig a bit deeper. Also looked at cksum as finders data size does not appear to give me what I wanted.

[Adam_Bell]

Hi, Mark;

From the man page for md5:

@man md5

Md5takes 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.

Originally written to detect any alteration in an encrypted message, the md5 algorithm is also a great “sameness” checker for copies of a file. It’s fast, apparently “computationally infeasible to produce two messages having the same message digest”, so if the message digests agree, the files are the same. The long hex number doesn’t have any “meaning” - it’s just a signature for the file.