GPG with SMP?

Thomas Harning Jr. harningt at
Wed Oct 5 16:38:37 CEST 2011

On Wednesday, October 5, 2011, Robert J. Hansen wrote:

> On 10/5/11 10:02 AM, Aaron Toponce wrote:
> > Does GnuPG support symmetric multiprocessing? If so, my Google-fu is
> > failing me, as is reading the available documentation. Reason I ask is
> > because encrypting 1TB files is fairly CPU intensive, and it appears that
> > it's only using 1 of my 4 cores.
> Short version: wouldn't do you any good even if it did.
> Long version: CTAK encryption isn't parallelizable: encrypting block N
> successfully depends on successfully encrypting block N-1, which in turn
> depends on successfully encrypting block N-3, and so on.  There's no way
> to partition it into independent subproblems.  A clever hack lets you
> parallelize decryption, but even then it's probably not worth it -- the
> amount of time spent doing disk I/O will be multiple orders of magnitude
> larger than the amount of time decrypting.
Certain modes of AES can be safely parallelizable in both directions:
 CTR can be since it uses a counter value to make each encryption different
for the XOR operation used.
 ESSIV or XTS are also useful in parallelization, but might need tweaking
for single-file encryption.

Thomas Harning Jr.
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