linux_kernel/security/keys/Kconfig

#
# Key management configuration
#

config KEYS
	bool "Enable access key retention support"
	select ASSOCIATIVE_ARRAY
	help
	  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.

config PERSISTENT_KEYRINGS
	bool "Enable register of persistent per-UID keyrings"
	depends on KEYS
	help
	  This option provides a register of persistent per-UID keyrings,
	  primarily aimed at Kerberos key storage.  The keyrings are persistent
	  in the sense that they stay around after all processes of that UID
	  have exited, not that they survive the machine being rebooted.

	  A particular keyring may be accessed by either the user whose keyring
	  it is or by a process with administrative privileges.  The active
	  LSMs gets to rule on which admin-level processes get to access the
	  cache.

	  Keyrings are created and added into the register upon demand and get
	  removed if they expire (a default timeout is set upon creation).

config BIG_KEYS
	bool "Large payload keys"
	depends on KEYS
	depends on TMPFS
	help
	  This option provides support for holding large keys within the kernel
	  (for example Kerberos ticket caches).  The data may be stored out to
	  swapspace by tmpfs.

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

config TRUSTED_KEYS
	tristate "TRUSTED KEYS"
	depends on KEYS && TCG_TPM
	select CRYPTO
	select CRYPTO_HMAC
	select CRYPTO_SHA1
	select CRYPTO_HASH_INFO
	help
	  This option provides support for creating, sealing, and unsealing
	  keys in the kernel. Trusted keys are random number symmetric keys,
	  generated and RSA-sealed by the TPM. The TPM only unseals the keys,
	  if the boot PCRs and other criteria match.  Userspace will only ever
	  see encrypted blobs.

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

config ENCRYPTED_KEYS
	tristate "ENCRYPTED KEYS"
	depends on KEYS
	select CRYPTO
	select CRYPTO_HMAC
	select CRYPTO_AES
	select CRYPTO_CBC
	select CRYPTO_SHA256
	select CRYPTO_RNG
	help
	  This option provides support for create/encrypting/decrypting keys
	  in the kernel.  Encrypted keys are kernel generated random numbers,
	  which are encrypted/decrypted with a 'master' symmetric key. The
	  'master' key can be either a trusted-key or user-key type.
	  Userspace only ever sees/stores encrypted blobs.

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