Part 1: General - Computer Security Resource Center - National ...

15. Private ephemeral key agreement key:
March, 2007
a. Type Considerations: Private ephemeral key agreement keys are the private key
elements of asymmetric key pairs that are used in a single transaction to establish one or
more keys. Private ephemeral key agreement keys may be used to establish symmetric
keys (e.g., key wrapping keys) or other secret keying material.
b. Cryptoperiod: Private ephemeral key agreement keys are used for a single key
agreement transaction. However, a private ephemeral key may be used multiple times to
establish the same symmetric key with multiple parties during the same transaction
(broadcast). The cryptoperiod of a private ephemeral key agreement key is the duration of
a single key agreement transaction.
16. Public ephemeral key agreement key:
a. Type Considerations: Public ephemeral key agreement keys are the public key
elements of asymmetric key pairs that are used only once to establish one or more keys.
b. Cryptoperiod: Public ephemeral key agreement keys are used for a single key
agreement transaction. The cryptoperiod of a public ephemeral key agreement key is the
duration of a single key agreement transaction.
17. Symmetric authorization key:
a. Type Considerations: A symmetric authorization key may be used for an extended
period of time, depending on the resources that are protected and the role of the entity
authorized for access. For this key type, the originator usage period and the recipient
usage period are the same, and therefore the equal to the cryptoperiod of the symmetric
authorization key. Primary considerations in establishing the cryptoperiod for symmetric
authorization keys include the robustness of the key, the adequacy of the cryptographic
method, and the adequacy of key protection mechanisms and procedures.
b. Cryptoperiod: Given the use of FIPS-Approved algorithms and key sizes, and an
expectation that the security of the key storage and use environment will increase as the
sensitivity and criticality of the authorization processes increases, it is recommended that
cryptoperiods be no more than two years.
18. Private authorization key:
a. Type Considerations: A private authorization key may be used for an extended period
of time, depending on the resources that are protected and the role of the entity authorized
for access. Primary considerations in establishing the cryptoperiod for private
authorization keys include the robustness of the key, the adequacy of the cryptographic
method, and the adequacy of key protection mechanisms and procedures. The
cryptoperiod of the private authorization key and its associated public key shall be the
same.
b. Cryptoperiod: Given the use of FIPS-Approved algorithms and key sizes, and an
expectation that the security of the key storage and use environment will increase as the
sensitivity and criticality of the authorization processes increases, it is recommended that
cryptoperiods for private authorization keys be no more than two years.
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