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

19. Public authorization key:
March, 2007
a. Type Considerations: A public authorization key is the public element of an
asymmetric key pair used to verify privileges for an entity that possesses the associated
private key. The length of the public authorization key cryptoperiod is of far less concern,
from a security point of view, than is that of the associated private key.
b. Cryptoperiod: The cryptoperiod of the public authorization key shall be the same as
the authorization private key: no more than two years.
Table 1 below is a summary of the cryptoperiods that are recommended for each key type.
Table 1: Recommended Cryptoperiods for key types 13
Key Type
Originator Usage
Period (OUP)
Cryptoperiod
Recipient Usage
Period
1. Private Signature Key 1-3 years
2. Public Signature Key Several years (depends on key size)
3. Symmetric Authentication
Key
< 2 years < OUP + 3 years
4. Private Authentication Key 1-2 years
5. Public Authentication Key 1-2 years
6. Symmetric Data Encryption
Keys
7. Symmetric Key Wrapping
Key
8. Symmetric and asymmetric
RNG Keys
< 2 years < OUP + 3 years
< 2 years < OUP + 3 years
Upon reseeding
9. Symmetric Master Key About 1 year
10. Private Key Transport Key < 2 years 14
11. Public Key Transport Key 1-2 years
13 In some cases risk factors affect the cryptoperiod selection (see Section 5.3.1).
14 . In certain email applications where received messages are stored and decrypted at a later time, the cryptoperiod
of the private key transport key may exceed the cryptoperiod of the public key transport key.
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