## Verify a file's message digest fingerprint (checksum) ##

[Author](authors.html): Alex Nikiforov nikiforov.al@gmail.com FreeBSD

[Reviewer](technical_reviewers.html): _name_ _[[contact]]_ _[[BSD_flavour]]_

[Reviewer](technical_reviewers.html): _name_ _[[contact]]_ _[[BSD_flavour]]_

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### Concept ###

Be familiar with the theory behind a message
digest(((message digest))) fingerprint and why it is important
to verify a file's fingerprint. In addition, be
able to create a fingerprint as well as verify an existing fingerprint(((fingerprint))).


### Introduction ###
When you download some file from a server and you don't trust this server how can you verify that file is real, without any bogus parts? You can use fingerprint of this file for verify it.

### Examples ###
You download **file** from some mirror in your country and want to verify it. Let's do it.

""\> md5 file 
MD5 (file) = d3762ac7a4e45f8262aeb3362bb1f9b7
\> sha1 file
SHA1 (file) = 67d59b7fe01074dba2462e13633bd163453bff47

Now we have fingerprint for **file** and can verify md5 and sha1 fingerprint from server.

TODO: show same with "openssl" and mention other digest types?

TODO: briefly mention cksum, checksums and block counts

### Practice Exercises ###
Get few fingerprints from your system via md5 and sha1

### More information ###

md5(1), openssl(1), sha1(1), cksum(1)


