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Independent Submission                                        S. LeonardRequest for Comments: 8351                                 Penango, Inc.Category: Informational                                        June 2018ISSN: 2070-1721The PKCS #8 EncryptedPrivateKeyInfo Media TypeAbstract   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 document is not an Internet Standards Track specification; it is   published for informational purposes.   This is a contribution to the RFC Series, independently of any other   RFC stream.  The RFC Editor has chosen to publish this document at   its discretion and makes no statement about its value for   implementation or deployment.  Documents approved for publication by   the RFC Editor are not candidates for any level of Internet Standard;   seeSection 2 of RFC 7841.   Information about the current status of this document, any errata,   and how to provide feedback on it may be obtained athttps://www.rfc-editor.org/info/rfc8351.Copyright Notice   Copyright (c) 2018 IETF Trust and the persons identified as the   document authors.  All rights reserved.   This document is subject toBCP 78 and the IETF Trust's Legal   Provisions Relating to IETF Documents   (https://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.Leonard                       Informational                     [Page 1]

RFC 8351       PKCS #8 EncryptedPrivateKeyInfo Media Type      June 2018Table of Contents1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .22.  Registration Application  . . . . . . . . . . . . . . . . . .23.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .64.  Security Considerations . . . . . . . . . . . . . . . . . . .65.  Normative References  . . . . . . . . . . . . . . . . . . . .6   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .71.  Introduction   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: Password-Based Cryptography Specification Version 2.1 as   published in [RFC2898] and updated by [RFC8018].  This document   registers the application/pkcs8-encrypted media type for the   EncryptedPrivateKeyInfo type of PKCS #8 (as originally described in   [RFC5208], which was obsoleted by [RFC5958]).  An instance of this   media type carries a single encrypted private key [RFC5958] BER-   encoded as a single EncryptedPrivateKeyInfo value.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] and [RFC8018]).  Such        algorithms take a password as input.  A "password" is a secret        text value (seeSection 3 of [RFC2898] and [RFC8018]), but for        algorithmic purposes the term "password" refers to an octet        string (seeSection 2 of [RFC2898] and [RFC8018]).  Therefore,        there must be some mapping between the text value (which might        be user input) and the octet string.Section 3 of [RFC2898]        (which was replaced by [RFC8018]) recommends "that applications        follow some common text encoding rules"; it then offers, but        does not recommend, ASCII and UTF-8.Leonard                       Informational                     [Page 2]

RFC 8351       PKCS #8 EncryptedPrivateKeyInfo Media Type      June 2018        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 (seeSection 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 cannot 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      Preparation, Enforcement, and Comparison of                     Internationalized Strings (PRECIS) password                     profile, i.e., OpaqueString fromSection 4 of                     [RFC7613], which was obsoleted by [RFC8265]: always                     UTF-8 in Normalization Form C (NFC).        *precis-XXX  Any profile from the IANA "PRECIS Profiles"                     registry where "XXX" is replaced by the profile                     name as shown in the 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.Leonard                       Informational                     [Page 3]

RFC 8351       PKCS #8 EncryptedPrivateKeyInfo Media Type      June 2018        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.  SeeSection 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], andSection 6 of PKCS #8 as originally described in      [RFC5208], which was obsoleted by [RFC5958]), 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      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 orLeonard                       Informational                     [Page 4]

RFC 8351       PKCS #8 EncryptedPrivateKeyInfo Media Type      June 2018      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:      RSA Laboratories PKCS #8 v1.2 RSA Encryption Standard, November      1993 (republished as [RFC5208], May 2008, and updated as      [RFC5958], August 2010);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): 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>   Intended usage: COMMON   Restrictions on usage: None.Leonard                       Informational                     [Page 5]

RFC 8351       PKCS #8 EncryptedPrivateKeyInfo Media Type      June 2018   Author/Change controller: Sean Leonard <dev+ietf@seantek.com>   Provisional registration?  No3.  IANA Considerations   IANA has registered the media type application/pkcs8-encrypted in the   Standards tree using the information provided inSection 2 of this   document.4.  Security Considerations   See the registration template.5.  Normative References   [CHARREG]  IANA, "Character Sets", December 2013,              <http://www.iana.org/assignments/character-sets>.   [IEEE.802.11-2012]              IEEE, "IEEE Standard for Information technology--              Telecommunications and information exchange between              systems Local and metropolitan area networks--Specific              requirements Part 11: Wireless LAN Medium Access Control              (MAC) and Physical Layer (PHY) Specifications",              IEEE 802.11-2012, DOI 10.1109/ieeestd.2012.6178212,              <http://ieeexplore.ieee.org/document/6178212/>.   [RFC2898]  Kaliski, B., "PKCS #5: Password-Based Cryptography              Specification Version 2.0",RFC 2898,              DOI 10.17487/RFC2898, September 2000,              <https://www.rfc-editor.org/info/rfc2898>.   [RFC2978]  Freed, N. and J. Postel, "IANA Charset Registration              Procedures",BCP 19,RFC 2978, DOI 10.17487/RFC2978,              October 2000, <https://www.rfc-editor.org/info/rfc2978>.   [RFC5208]  Kaliski, B., "Public-Key Cryptography Standards (PKCS) #8:              Private-Key Information Syntax Specification Version 1.2",RFC 5208, DOI 10.17487/RFC5208, May 2008,              <https://www.rfc-editor.org/info/rfc5208>.   [RFC5958]  Turner, S., "Asymmetric Key Packages",RFC 5958,              DOI 10.17487/RFC5958, August 2010,              <https://www.rfc-editor.org/info/rfc5958>.Leonard                       Informational                     [Page 6]

RFC 8351       PKCS #8 EncryptedPrivateKeyInfo Media Type      June 2018   [RFC7292]  Moriarty, K., Ed., Nystrom, M., Parkinson, S., Rusch, A.,              and M. Scott, "PKCS #12: Personal Information Exchange              Syntax v1.1",RFC 7292, DOI 10.17487/RFC7292, July 2014,              <https://www.rfc-editor.org/info/rfc7292>.   [RFC7613]  Saint-Andre, P. and A. Melnikov, "Preparation,              Enforcement, and Comparison of Internationalized Strings              Representing Usernames and Passwords",RFC 7613,              DOI 10.17487/RFC7613, August 2015,              <https://www.rfc-editor.org/info/rfc7613>.   [RFC8018]  Moriarty, K., Ed., Kaliski, B., and A. Rusch, "PKCS #5:              Password-Based Cryptography Specification Version 2.1",RFC 8018, DOI 10.17487/RFC8018, January 2017,              <https://www.rfc-editor.org/info/rfc8018>.   [RFC8265] Saint-Andre, P. and A. Melnikov, "Preparation, Enforcement,              and Comparison of Internationalized Strings Representing              Usernames and Passwords",RFC 8265, DOI 10.17487/RFC8265,              October 2017, <https://www.rfc-editor.org/info/rfc8265>.Author's Address   Sean Leonard   Penango, Inc.   5900 Wilshire Blvd   Ste 2600   Los Angeles, CA  90036   United States of America   Email: dev+ietf@seantek.com   URI:http://www.penango.com/Leonard                       Informational                     [Page 7]