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 Restrictions on usage: None. Author/Change controller: Sean Leonard 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", , 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]