OpenSSH slow on OSX High Sierra (maybe due to libcrypto)?

Darren Tucker dtucker at
Thu Jul 12 18:10:38 AEST 2018

Hi all.

Is anyone else seeing issues with OpenSSH being slow on OSX High
Sierra?  In the interests of better test coverage I set one up,
however the OpenSSH tests take much longer on it than on much older
machines with much slower CPUs. It seems to be due to the
vendor-supplied libcrypto being about 20x slower at bignum operations
than nominally the same version of LibreSSL compiled locally.

If anyone has such a machine handy, could you please run "sysctl
machdep.cpu.brand_string; /usr/bin/openssl speed rsa" and post the
results for comparison?

$ uname -a
Darwin osx-highsierra 17.6.0 Darwin Kernel Version 17.6.0: Tue May  8
15:22:16 PDT 2018; root:xnu-4570.61.1~1/RELEASE_X86_64 x86_64
$ sysctl machdep.cpu.brand_string
machdep.cpu.brand_string: Intel(R) Core(TM) i5-2415M CPU @ 2.30GHz
$ /usr/bin/openssl speed rsa
LibreSSL 2.2.7
built on: date not available
options:bn(64,64) rc4(ptr,int) des(idx,cisc,16,int) aes(partial) blowfish(idx)
compiler: information not available
rsa  512 bits 0.000964s 0.000059s   1037.3  16987.1
rsa 1024 bits 0.006052s 0.000271s    165.2   3687.3
rsa 2048 bits 0.040528s 0.001145s     24.7    873.6
rsa 4096 bits 0.278889s 0.004272s      3.6    234.1

$ libressl-2.2.7/apps/openssl speed rsa
options:bn(64,64) rc4(16x,int) des(idx,cisc,16,int) aes(partial)
idea(int) blowfish(idx)
compiler: information not available
                  sign    verify    sign/s verify/s
rsa  512 bits 0.000074s 0.000008s  13466.5 130066.4
rsa 1024 bits 0.000271s 0.000017s   3690.6  57557.5
rsa 2048 bits 0.001665s 0.000054s    600.6  18684.4
rsa 4096 bits 0.011938s 0.000195s     83.8   5121.7

Darren Tucker (dtucker at
GPG key 11EAA6FA / A86E 3E07 5B19 5880 E860  37F4 9357 ECEF 11EA A6FA (new)
    Good judgement comes with experience. Unfortunately, the experience
usually comes from bad judgement.

More information about the openssh-unix-dev mailing list