[pkg-gnupg-maint] Bug#848951: Bug#848951: gnupg: Utilize multiple cores on CPU for encryption and decryption (and compression)

[Werner Koch]

On Wed, 21 Dec 2016 17:47, witold.baryluk at gmail.com said:

> Everybody know CTR is easy to parallelize and easy to understand implement,

CTR is a reincarnation of RC4 - bug wise.  Nobody with a sane mind wants
a counter mode.  It is also not an AE mode and thus nothing to be used
for new protocols.

> CCM is another options -
> http://csrc.nist.gov/groups/ST/toolkit/BCM/documents/proposedmodes/ccm/ccm.pdf

FWIW, here are the numbers fro current Libgcrypt on amd64:

 AES            |  nanosecs/byte   mebibytes/sec   cycles/byte
        CFB enc |      1.77 ns/B     537.9 MiB/s      4.08 c/B  -- non-AE
        CFB dec |     0.373 ns/B    2554.7 MiB/s     0.859 c/B  -- non-AE
        CTR enc |     0.396 ns/B    2409.6 MiB/s     0.910 c/B  -- non-AE
        CTR dec |     0.396 ns/B    2409.9 MiB/s     0.910 c/B  -- non-AE
        CCM enc |      2.19 ns/B     435.6 MiB/s      5.04 c/B
        CCM dec |      2.25 ns/B     423.7 MiB/s      5.18 c/B
        GCM enc |      1.07 ns/B     890.9 MiB/s      2.46 c/B
        GCM dec |      1.07 ns/B     890.8 MiB/s      2.46 c/B
        OCB enc |     0.440 ns/B    2165.9 MiB/s      1.01 c/B
        OCB dec |     0.453 ns/B    2107.5 MiB/s      1.04 c/B

So, CCM is pretty slow.  The whole reason why we have that slow CCM is
due to patent fears.  And it is cumbersome to work with.

> still most of the work can be parallelized, and if authentication stage is
> faster than encryption, it should not be a bottlneck for performance.

It is anyway I/O bounded.  This is why I wrote theoretical speedup.

For backing up large amounts of data, gpg is not an optimal tool.  If
there is a real need for a faster tool we could add one to GnuPG which
does only one thing (symmetric encryption) without the various options
possible in OpenPGP.  bugs.gnupg.org has a “wish” category.


Salam-Shalom,

   Werner

-- 
Die Gedanken sind frei.  Ausnahmen regelt ein Bundesgesetz.
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