On traditional IOS routers SSH is enable if you have K9 software, ssh server enabled and proper pair of key generated on device. It seems that IOS XR works differently. SSH is enabled and working even if you have no keys generated.
When you try to connect to such router you get following message:

Anomander:~ peper$ ssh [email protected]
no hostkey alg

and in router logs:

RP/0/RSP0/CPU0:ASR9K#RP/0/RSP0/CPU0:Oct 29 13:18:20.167 : SSHD_[65804]: %SECURITY-SSHD-3-ERR_ERRNO : Failed to retreive host key-pair No error

No error? Well, there is an error – no keys were generated. This is cosmetic, but would be nice if SSH wouldn’t work at all until proper keys are generated or no misleading error message would be displayed.