RFC 2876 (rfc2876) - Page 2 of 13
Use of the KEA and SKIPJACK Algorithms in CMS
Alternative Format: Original Text Document
RFC 2876 KEA and SKIPJACK Algorithms in CMS July 2000
3. Content Decryption Process
This section applies to the processing of both the enveloped-data and
encrypted-data content types. The encryptedContent MUST be decrypted
as a single string using the SKIPJACK algorithm in 64-bit CBC mode.
The 80-bit SKIPJACK CEK and the 8-byte IV MUST be used as inputs to
the SKIPJACK decryption process. Following decryption, the padding
MUST be removed from the decrypted data. The padding rules are
described in [CMS] Section 6.3, "Content-encryption Process".
4. Enveloped-data Conventions
The CMS enveloped-data content type consists of an encrypted content
and wrapped CEKs for one or more recipients. Compliant software MUST
meet the requirements for constructing an enveloped-data content type
stated in [CMS] Section 6, "Enveloped-data Content Type". [CMS]
Section 6 should be studied before reading this section, because this
section does not repeat the [CMS] text.
An 8-byte IV and 80-bit CEK MUST be randomly generated for each
instance of an enveloped-data content type as inputs to the SKIPJACK
algorithm for use to encrypt the content. The SKIPJACK CEK MUST only
be used for encrypting the content of a single instance of an
enveloped-data content type.
KEA and SKIPJACK can be used with the enveloped-data content type
using either of the following key management techniques defined in
[CMS] Section 6:
1) Key Agreement: The SKIPJACK CEK is uniquely wrapped for each
recipient using a pairwise symmetric key-encryption key (KEK)
generated using KEA using the originator's private KEA key,
recipient's public KEA key and other values. Section 4.2 provides
additional details.
2) "Previously Distributed" Symmetric KEK: The SKIPJACK CEK is
wrapped using a "previously distributed" symmetric KEK (such as a
Mail List Key). The methods by which the symmetric KEK is
generated and distributed are beyond the scope of this document.
Section 4.3 provides more details.
[CMS] Section 6 also defines the concept of the key transport key
management technique. The key transport technique MUST NOT be used
with KEA.
Pawling Informational