I've seen on a lot of sites "checksum" hashes to verify the integrity of downloaded files.

What are them and how do I use them?

Ex: I have a downloaded-file.tar on the current working directory and I want to verify it, what command should I use?


From the wikipedia's "Checksum" article:

A checksum or hash sum is a small-size datum from a block of digital data for the purpose of detecting errors which may have been introduced during its transmission or storage. It is usually applied to an installation file after it is received from the download server. By themselves checksums are often used to verify data integrity, but should not be relied upon to also verify data authenticity

Usage depends on the encryption, for example the following ways are both valid:

> sha256sum -c - <<<"{hash} *downloaded-file.tar"
> md5sum -c - <<<"{hash} *downloaded-file.tar"

where {hash} is replaced with the corresponding value.

  • @josten usage is the same? I'm not an expert on this, feel free to edit the answer ;) – laconbass May 21 '15 at 22:08

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