PKCS #8: Private-Key Information Content Types
Extracted elements (8)
Content type assignments for PrivateKeyInfo and EncryptedPrivateKeyInfo were needed so these structures could be carried in CMS (RFC 5652); media types application/pkcs8 and application/pkcs8-encrypted had been assigned long ago but formal CMS content type OIDs were missing.
RFC 5958 revised the original RFC 5208 syntax to include AsymmetricKeyPackage supporting multiple PrivateKeyInfos; this document defines content types for exactly one PrivateKeyInfo and one EncryptedPrivateKeyInfo for CMS carriage.
The EncryptedPrivateKeyInfo content type is identified by OID id-ct-encrPrivateKeyInfo (1.2.840.113549.1.9.16.1.53), enabling EncryptedPrivateKeyInfo to be carried in CMS.
The PrivateKeyInfo content type is identified by OID id-ct-privateKeyInfo (1.2.840.113549.1.9.16.1.52), enabling PrivateKeyInfo to be carried in CMS.
IANA assigned OID decimal 52 (id-ct-privateKeyInfo) and decimal 53 (id-ct-encrPrivateKeyInfo) in the 'SMI Security for S/MIME CMS Content Type (1.2.840.113549.1.9.16.1)' registry, and OID decimal 85 (id-mod-pkcs8ContentType) in the 'SMI Security for S/MIME Module Identifier' registry.
IANA updated the application/cms media type registration to add privateKeyInfo and encrPrivateKeyInfo as Inner Content Types (ICTs) and to reference RFC 9939 in interoperability and security considerations sections.
The security considerations of RFC 5958 (Asymmetric Key Packages) apply to the content types defined in this document.
The ASN.1 module PrivateKeyInfoContentTypes imports CONTENT-TYPE from CMS-2009 (RFC 5911) and PrivateKeyInfo/EncryptedPrivateKeyInfo from AsymmetricKeyPackageModuleV1 (RFC 5958), defining ct-privateKeyInfo and ct-encrPrivateKeyInfo content types.