Enable access key retention support

configname: CONFIG_KEYS

Linux Kernel Configuration
└─>Security options
└─>Enable access key retention support
In linux kernel since version 2.6.12  
This option provides support for retaining authentication tokens and
access keys in the kernel.

It also includes provision of methods by which such keys might be
associated with a process so that network filesystems, encryption
support and the like can find them.

Furthermore, a special type of key is available that acts as keyring:
a searchable sequence of keys. Each process is equipped with access
to five standard keyrings: UID-specific, GID-specific, session,
process and thread.

If you are unsure as to whether this is required, answer N.

is selected by
CONFIG_CIFS_UPCALL

is depended by
CONFIG_NFS_V4
CONFIG_CIFS