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Multithreaded Encryption and Compression

Submitted by on November 24, 2014 – 9:13 am 5 Comments

One problem with encryption is it’s a slow and resource-intensive process. While most encryption software lacks multithreading support, it is possible to use the GNU Parallel to take full advantage of modern multi-core CPUs to greatly speedup encryption and decryption. Below are a few examples showing how to use parallel with gpg. I also included some examples of using tar and pigz (multithreaded gzip).

I suggest you create a directory with a bunch of small files and use it as your sandbox to test encryption/decryption before you move on to the real data. Here is a script that will generate a dummy folder structure with  a few thousand small, randomly-generate files. You can read more about this script here.

Note: for the sake of simplicity I am using gpg password encryption. For better security, in real life you should be using gpg with encryption key.

Install tools:

yum -y install pigz gpg parallel

To install parallel from source:

cd /tmp ; wget ; bzip2 -d parallel-latest.tar.bz2 ; tar xvf parallel-latest.tar ; cd parallel-[0-9]* ; ./configure ; make ; make install

On Solaris 10/11:

# Install OpenCSW
pkgadd -d
/opt/csw/bin/pkgutil -U
/opt/csw/bin/pkgutil -a vim
/opt/csw/bin/pkgutil -y -i vim

# Install tools
/opt/csw/bin/pkgutil -i pigz
/opt/csw/bin/pkgutil -i parallel
/opt/csw/bin/pkgutil -i gnupg

Set dir and number of cores:

dir=test ; cores=`grep -c '^processor' /proc/cpuinfo`

On Solaris 10/11:

/usr/bin/kstat -m cpu_info | egrep "chip_id|core_id|module: cpu_info" | grep 'module: cpu_info' | awk '{ print $4 }' | sort -u | wc -l | tr -d ' '

Encrypt all files in a directory:

find "${dir}" -type f -not -iname "*.gpg" | sort | parallel --gnu -j $${cores} --workdir "$PWD" 'echo "Encrypting {}" ; gpg --batch --symmetric --passphrase MySecretPassword1 -z 2 "{}" >/dev/null 2>&1'

Delete original non-encrypted files:

find "${dir}" -type f -not -iname "*.gpg" -exec /bin/rm -f "{}" \;

Decrypt all encrypted files in a directory:

find "${dir}" -type f -iname "*.gpg" | sort | parallel --gnu -j $${cores} 'echo "Decrypting {}" ; gpg --batch --decrypt --passphrase MySecretPassword1 --output "{.}" "{}"'

Delete original encrypted file:

find "${dir}" -type f -iname "*.gpg" -exec /bin/rm -f "{}" \;

Create compressed tarball with pigz:

tar cf - "${dir}" | pigz -9 -p $${cores} > "${dir}.tar.gz"

Create compressed encrypted tarball with pigs and gpg:

tar c "${dir}" | pigz -9 -p 30 | gpg --batch --symmetric --passphrase MySecretPassword1 > "${dir}.tar.gz.pgp"

Decrypt compressed tarball:

gpg --batch --decrypt --passphrase MySecretPassword1 -o ${dir}.tar.gz ${dir}.tar.gz.pgp


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  • Avatar OleTange says:

    GNU Parallel defaults to -j number_of_cores, so you do no need that. Also you do not need ” around {}.

    • Avatar igor444 says:

      GNU parallel defaults to 9 threads if -j is not specified. See here:

      An alternative is to specify “-j +0”, allowing parallel to automatically determine the number of core. However, this doesn’t always work on Linux and never works on SPARC Solaris.

      It is a good practice to enclose variables in double quotes, thus saving yourself a lot of trouble when the variable’s value happens to contain a space or a special character.

      • Avatar OleTange says:

        Being the author of GNU Parallel I see myself as a more authoritative source than admin-magazine. GNU Parallel _used_ to default to 9 processes. It was changed in 20110122 after a user vote.

        While it is good practice to enclose VARIABLES in double quotes, that is not the case with {} (which is not a variable but a replacement string).

        GNU Parallel deals with the spacing, so putting ” around is always unneeded and can cause harm in some situations. Here for example: parallel echo ‘a “{}”‘ ::: ‘a b’

        • Avatar igor444 says:

          Point taken on the double-quotes. Thanks.

          I noticed on SPARC T4-2 parallel launches 16 threads with or without the –use-cpus-instead-of-cores. I would have expected 128 – the number of vcores.

          • Avatar OleTange says:

            Core detection is not tested very well on SPARC: I do not have access to a T4-2, so I rely on users to provide improvements. Feel free to do so.

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