IETF RFC 6032 PDF

This document defines the Cryptographic Message Syntax (CMS) encrypted key package content type, which can be used to encrypt a content that includes a key package, such as a symmetric key package or an asymmetric key package. It is transport independent. CMS can be used to digitally sign, digest, authenticate, or further encrypt this content type. It is designed to be used with the CMS Content Constraints (CCC) extension, which does not constrain the EncryptedData, EnvelopedData, and AuthEnvelopedData.