Re: [dm-crypt] bits vs bytes

Michael Kjörling
2020-03-30T20:25:06Z

On 30 Mar 2020 20:03 +0000, from moreejt@yahoo.com (JT Morée):
> When I run luksDump i see that multiple locations give sizes in
> 'bits'.  Is that correct?   Normally, we operate in 8 bit => bytes.
> If I read this correctly then
>
> 2: luks2 (unbound)
>   Key:        512 bits = 64 bytes

Cryptographic key sizes, hash lengths, block sizes, and similar
quantities are commonly stated in bits, not bytes, especially for
algorithms typically implemented on digital, binary computers (in
either hardware or software).

There's likely a variety of reasons for this; some historical, some
mathematical.

Certainly you can convert the number of bits to a number of bytes by
dividing by 8 _if_ you prefer that for some reason, but a _lot_ more
people will know what you mean if you say, for example, "128-bit AES"
than "16-byte AES". (Never mind "AES-128" versus "AES-16", the latter
of which seems likely to just be confusing.) So for communicating with
others, I _really_ suggest using the more common form.

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Michael Kjörling • https://michael.kjorling.se • michael@kjorling.se
“Remember when, on the Internet, nobody cared that you were a dog?”