Internet DRAFT - draft-seantek-pkcs8-encrypted
draft-seantek-pkcs8-encrypted
Network Working Group S. Leonard
Internet-Draft Penango, Inc.
Intended Status: Informational November 14, 2017
Expires: May 18, 2018
The PKCS #8 EncryptedPrivateKeyInfo Media Type
draft-seantek-pkcs8-encrypted-03
Abstract
This document registers the application/pkcs8-encrypted media type
for the EncryptedPrivateKeyInfo type of PKCS #8. An instance of this
media type carries a single encrypted private key, BER-encoded as a
single EncryptedPrivateKeyInfo value.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Leonard Exp. May 18, 2018 [Page 1]
Internet-Draft PKCS #8 Encrypted Media Type November 2017
1. Definitions
The key words "SHOULD", "SHOULD NOT", and "RECOMMENDED" in this
document are to be interpreted as described in [RFC2119].
2. Registration Application
Type name: application
Subtype name: pkcs8-encrypted
Required parameters: None.
Optional parameters:
password-mapping: The private key is encrypted with an encryption
algorithm, which could be a password-based encryption scheme as
that term is used in PKCS #5 [RFC2898]. Such algorithms take a
password as input. A "password" is a secret text value (Section 3
of PKCS #5), but for algorithmic purposes the term "password"
refers to an octet string (Section 2 of PKCS #5). Therefore, there
must be some mapping between the text value (which might be user
input) and the octet string. Section 3 of PKCS #5 recommends "that
applications follow some common text encoding rules"; it then
offers, but does not recommend, ASCII and UTF-8.
While many modern applications support Unicode and Unicode-based
encodings such as UTF-8 and UTF-16, interchange is still needed
with private key artifacts that are encrypted with passwords in
other encodings. Therefore, this parameter specifies the charset
(see Section 1.3 of [RFC2978]) that a recipient SHOULD attempt
first, in "reverse", when mapping from a sequence of characters to
an octet string. This parameter is not cryptographically protected,
so recipients SHOULD NOT rely on it as the exclusive mapping
possibility.
This parameter has similar semantics to the charset parameter from
text/plain, except that it only applies to the user's input (text
value) of a password. There is no default value.
The following special values, which all begin with "*" to
distinguish them from registered charsets, are defined:
*pkcs12 = UTF-16LE with U+0000 NULL terminator: PKCS #12-style,
see [RFC7292]
*precis = PRECIS password profile, i.e., OpaqueString from
Section 4 of [RFC7613]: always UTF-8 in Normalization
Form C (NFC)
*precis-XXX = PRECIS profile as named XXX in the IANA PRECIS
Leonard Exp. May 18, 2018 [Page 2]
Internet-Draft PKCS #8 Encrypted Media Type November 2017
Profiles Registry
*hex = hexadecimal input: the input is mapped to 0-9, A-F,
and then converted directly to octets. If there are
an odd number of hex digits, either the final digit 0
is appended, or an error condition is raised. Compare
with Annex M.4 of IEEE 802.11-2012.
*dtmf = The characters "0"-"9", "A"-"D", "*", and "#", which
map to their corresponding ASCII codes. "A"-"D" map
to the uppercase range 0x41 - 0x44. (This is to
support restricted-input devices, i.e., telephones
and telephone-like equipment.) User input outside of
these values is either ignored, or an error condition
is raised.
Otherwise, the value of this parameter is a charset, from the IANA
Character Sets Registry [CHARREG].
This parameter is case-insensitive.
Encoding considerations: Binary.
Security considerations:
Carries a cryptographic private key. See Section 6 of [RFC5958].
EncryptedPrivateKeyInfo PKCS #8 data contains exactly one private
key. Poor password choices, weak algorithms, or improper parameter
selections (e.g., insufficient salting rounds) will make the
confidential payloads much easier to compromise.
Interoperability considerations:
PKCS #8 is a widely recognized format for private key information
on all modern cryptographic stacks. The contents are exactly one
private key (with optional key attributes), so there is no
possibility for hidden "Easter eggs" in the payload such as
unexpected certificates or miscellaneous secrets.
The encrypted variation in this registration,
EncryptedPrivateKeyInfo (Section 3, Encrypted Private Key Info, of
[RFC5958], and Section 6 of PKCS #8), is less widely used for
exchange than PKCS #12, but it is much simpler to implement.
Actually PKCS #12 incorporates the PKCS #8 types, so a PKCS #12
processor ought to be able to process PKCS #8 data by embedding the
PKCS #8 data in PKCS #12 "scaffolding".
The password-mapping parameter aids in interoperability when the
creator (who encrypted the keying material) and the user (who is
Leonard Exp. May 18, 2018 [Page 3]
Internet-Draft PKCS #8 Encrypted Media Type November 2017
attempting to decrypt the keying material) are not operating in the
same character encoding environment. An anticipated scenario is
that the creator may have created the keying material with a
password in a Shift-JIS environment a long time ago, while the user
is in a UTF-8 environment. There are potentially many Unicode
sequences that code for the same abstract character, such as
precomposed and decomposed forms; yet, such an abstract character
(however coded in Unicode) will tend to map to one coding in the
legacy charset, if it can be represented at all. Therefore, the
password-mapping parameter will almost never be ambiguous when
mapping to legacy encodings. When mapping from one Unicode form to
another (such as an internal Unicode representation to *pkcs12),
code sequences are either preserved, or folded deterministically to
common Unicode code points or sequences, producing the same
holistic result as mapping to legacy encodings.
It is possible that an abstract character might map to multiple
legacy encodings under the same charset. However, the possibility
is sufficiently remote as to be ignored in this media type
registration. One possible workaround is to set the user's
(decrypting party's) local operating environment to the password-
mapping legacy encoding parameter for the purpose of generating the
password octet string from user input. Another possibility is to
generate all possible legacy encoding combinations from the
abstract text (i.e., Unicode text), attempting decryption with
them. Customized behavior can be defined by updating this media
type registration with a new password-mapping special value,
prefixed with *.
Published specification:
PKCS #8 v1.2, November 1993 (republished as RFC 5208, May 2008);
RFC 5958, August 2010
Applications that use this media type:
Machines, applications, browsers, Internet kiosks, and so on, that
support this standard allow a user to import, export, and exercise
a single private key.
Fragment identifier considerations: None.
Additional information:
Deprecated alias names for this type: N/A
Magic number(s): None.
File extension(s): .p8e
Macintosh file type code(s):
Leonard Exp. May 18, 2018 [Page 4]
Internet-Draft PKCS #8 Encrypted Media Type November 2017
None. A uniform type identifier (UTI) of
"com.rsa.pkcs-8-encrypted" is RECOMMENDED.
Object Identifiers: 1.2.840.113549.1.12.10.1.2 (when in PKCS #12)
Person & email address to contact for further information:
Sean Leonard <dev+ietf@seantek.com>
Restrictions on usage: None.
Author/Change controller: Sean Leonard <dev+ietf@seantek.com>
Intended usage: COMMON
Provisional registration? No
3. IANA Considerations
IANA is asked to register the media type application/pkcs8-encrypted
in the Standards tree using the applications provided in Section 1 of
this document.
4. Security Considerations
See the registration template.
5. Normative References
[CHARREG] IANA, "Character Sets",
<http://www.iana.org/assignments/character-sets>, December
2013.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2898] Kaliski, B., "PKCS #5: Password-Based Cryptography
Specification Version 2.0", RFC 2898, September 2000.
[RFC2978] Freed, N. and J. Postel, "IANA Charset Registration
Procedures", BCP 19, RFC 2978, October 2000.
[RFC5208] Kaliski, B., "Public-Key Cryptography Standards (PKCS) #8:
Private-Key Information Syntax Specification Version 1.2",
RFC 5208, May 2008.
[RFC5958] Turner, S., "Asymmetric Key Packages", RFC 5958, August
2010.
Leonard Exp. May 18, 2018 [Page 5]
Internet-Draft PKCS #8 Encrypted Media Type November 2017
[RFC7292] Moriarty, K., Nystrom, S., Parkinson, S., Rusch, A., and
M. Scott, "PKCS #12: Personal Information Exchange Syntax
v1.1", RFC 7292, July 2014.
[RFC7613] Saint-Andre, P. and A. Melnikov, "Preparation,
Enforcement, and Comparison of Internationalized Strings
Representing Usernames and Passwords", RFC 7613, August
2015.
Author's Address
Sean Leonard
Penango, Inc.
5900 Wilshire Blvd
Ste 2600
Los Angeles, CA 90036
USA
EMail: dev+ietf@seantek.com
URI: http://www.penango.com/
Appendix A. Changes from -02 to -03
Updated the document based on discussions. Added much more
explanatory text about the password-mapping parameter.
Leonard Exp. May 18, 2018 [Page 6]
