Re: proposed key usaged text -- the final round

[Ed Gerck <egerck@xxxxxxx>]

Russ Housley wrote:

> To people who still care about NR:
>
> In a last ditch hope of settling the key usage debate Tim Polk and I have
> made minor adjustments to the key usage text.  We hope that this is text
> that everyone can live with (but we know that there are some people who
> will feel compelled to argue on and on and on and on and on and on ...).

Russ and Tim:

Fine. The changes are IMO enough to capture the main points that I saw
worthwhile to discuss on and on and on ;-)  The inclusion of "falsely"
is now also in IMO fine, because it is clearly seen from the relying-party
viewpoint.   I have just one minor comment that is most probably just a
text glitch that can easily be corrected:

The text:

 The dataEncipherment bit is asserted when the subject public key
 is used for enciphering user data, other than cryptographic keys.

should be:

 The dataEncipherment bit is asserted when the subject public key
 is used for enciphering data other than cryptographic keys.

[i.e., deleted "user" and the comma]

Thank you both for the fine job!

Have a Great Thanksgiving.

Cheers,

Ed Gerck

>
> ----Proposed text for 4.2.1.3 Key Usage
>
> 4.2.1.3  Key Usage
>
>     The key usage extension defines the purpose (e.g., encipherment, sig-
>     nature, certificate signing) of the key contained in the certificate.
>     The usage restriction might be employed when a key that could be used
>     for more than one operation is to be restricted.  For example, when
>     an RSA key should be used only for signing, the digitalSignature
>     and/or nonRepudiation bits would be asserted. Likewise, when an RSA
>     key should be used only for key management, the keyEncipherment bit
>     would be asserted. When used, this extension SHOULD be marked criti-
>     cal.
>
>        id-ce-keyUsage OBJECT IDENTIFIER ::=  { id-ce 15 }
>
>        KeyUsage ::= BIT STRING {
>             digitalSignature        (0),
>             nonRepudiation          (1),
>             keyEncipherment         (2),
>             dataEncipherment        (3),
>             keyAgreement            (4),
>             keyCertSign             (5),
>             cRLSign                 (6),
>             encipherOnly            (7),
>             decipherOnly            (8) }
>
>     Bits in the KeyUsage type are used as follows:
>
>        The digitalSignature bit is asserted when the subject public key
>        is used with a digital signature mechanism to support security
>        services other than non-repudiation (bit 1), certificate signing
>        (bit 5), or revocation information signing (bit 6). Digital signa-
>        ture mechanisms are often used for entity authentication and data
>        origin authentication with integrity.
>
>        The nonRepudiation bit is asserted when the subject public key is
>        used to verify digital signatures used to provide a non-repudiation
>        service.  This service protects against the certificate subject
>        falsely denying signing the data, excluding certificate or CRL
>        signing. In the case of later conflict, a reliable third party may
>        determine the authenticity of the signed data.
>
>        Further distinctions between the digitalSignature and nonRepudiation
>        bits may be provided in specific certificate policies.  The values
>        of the digitalSignature and nonRepudiation bits is insufficient to
>        determine the intentions of the certificate subject.  The context
>        in which the data was signed MUST also be considered.  A signature
>        policy identifier embedded in the signed data MAY be used to
>        explicitly provide context.
>
>        The keyEncipherment bit is asserted when the subject public key is
>        used for key transport.  For example, when an RSA key is to be
>        used for key management, then this bit shall asserted.
>
>        The dataEncipherment bit is asserted when the subject public key
>        is used for enciphering user data, other than cryptographic keys.
>
>        The keyAgreement bit is asserted when the subject public key is
>        used for key agreement.  For example, when a Diffie-Hellman key is
>        to be used for key management, then this bit shall asserted.
>
>        The keyCertSign bit is asserted when the subject public key is
>        used for verifying a signature on certificates.  This bit may only
>        be asserted in CA certificates.  If the keyCertSign bit is
>        asserted, then the cA bit in the basic constraints extension (see
>        4.2.1.10) MUST also be asserted. If the keyCertSign bit is not
>        asserted, then the cA bit in the basic constraints extension MUST
>        NOT be asserted.
>
>        The cRLSign bit is asserted when the subject public key is used
>        for verifying a signature on revocation information (e.g., a CRL).
>
>        The meaning of the encipherOnly bit is undefined in the absence of
>        the keyAgreement bit.  When the encipherOnly bit is asserted and
>        the keyAgreement bit is also set, the subject public key may be
>        used only for enciphering data while performing key agreement.
>
>        The meaning of the decipherOnly bit is undefined in the absence of
>        the keyAgreement bit.  When the decipherOnly bit is asserted and
>        the keyAgreement bit is also set, the subject public key may be
>        used only for deciphering data while performing key agreement.
>
>     This profile does not restrict the combinations of bits that may be
>     set in an instantiation of the keyUsage extension.  However,
>     appropriate values for keyUsage extensions for particular algorithms
>     are specified in section 7.3.