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

March, 2007
of keying material and other related information. An “OK” indicates that storage is permissible,
but not necessarily required. The final determination for backup should be made based on the
application in which the keying material is used. A detailed discussion about each type of key
and other cryptographic information is provided in Appendix B.3.
Keying material maintained in backup should remain in storage for at least as long as the same
keying material is maintained in storage for normal operational use (see Section 8.2.1). When no
longer needed for normal operational use, the keying material and other related information
should be removed from backup storage. When removed from backup storage, all traces of the
information shall be destroyed in accordance with Section 8.3.4.
A discussion of backup and recovery is provided in [ITLBulletin].
Table 7: Backup of keys
Type of Key Backup?
Private signature key No (in general); non-repudiation would be in question.
However, it may be warranted in some cases - a CA’s
signing private key, for example. When required, any
backed up keys shall be stored under the owner’s control.
Public signature verification key OK; its presence in a public-key certificate that is available
elsewhere may be sufficient.
Symmetric authentication key OK
Private authentication key OK, if required by an application.
Public authentication key OK; its presence in a public-key certificate that is available
elsewhere may be sufficient.
Symmetric data encryption key OK
Symmetric key wrapping key OK
Random number generation key Not necessary and may not be desirable, depending on the
application.
Symmetric master key OK
Private key transport key OK
Public key transport key OK; its presence in a public-key certificate that is available
elsewhere may be sufficient.
Symmetric key agreement key OK
Private static key agreement key No, unless needed for reconstruction during key recovery.
However, when ephemeral information (e.g., a private
ephemeral key agreement key) is used in a key agreement
scheme, knowledge of the private static key agreement key
and any public keys will not be sufficient.
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