Something

sabayonuser@localhost ~ $ su
Password:
localhost sabayonuser #  echo "app-crypt/openssl-tpm-engine ~amd64" >> /etc/portage/package.keywords && emerge -av openssl-tpm-engine

These are the packages that would be merged, in order:

Calculating dependencies \
!!! All ebuilds that could satisfy "openssl-tpm-engine" have been masked.
!!! One of the following masked packages is required to complete your request:
- app-crypt/openssl-tpm-engine-0.4.1 (masked by: missing keyword)

For more information, see MASKED PACKAGES section in the emerge man page or
refer to the Gentoo Handbook.

localhost sabayonuser #  echo "app-crypt/openssl-tpm-engine-0.4.1 ~amd64" >> /etc/portage/package.keywords && emerge -av openssl-tpm-engine-0.4.1
--- Invalid atom in /etc/portage/package.keywords: app-crypt/openssl-tpm-engine-0.4.1

These are the packages that would be merged, in order:

Calculating dependencies /

!!! 'openssl-tpm-engine-0.4.1' is not a valid package atom.
!!! Please check ebuild(5) for full details.
!!! (Did you specify a version but forget to prefix with '='?)
localhost sabayonuser #