TOC 
Network Working GroupM. Jones
Internet-DraftMicrosoft
Intended status: Standards TrackE. Rescorla
Expires: May 2, 2012RTFM, Inc.
 J. Hildebrand
 Cisco Systems, Inc.
 October 30, 2011


JSON Web Encryption (JWE)
draft-jones-json-web-encryption-01

Abstract

JSON Web Encryption (JWE) is a means of representing encrypted content using JSON data structures. Related signature capabilities are described in the separate JSON Web Signature (JWS) specification.

Requirements Language

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 (Bradner, S., “Key words for use in RFCs to Indicate Requirement Levels,” March 1997.) [RFC2119].

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.”

This Internet-Draft will expire on May 2, 2012.

Copyright Notice

Copyright (c) 2011 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.



Table of Contents

1.  Introduction
2.  Terminology
3.  JSON Web Encryption (JWE) Overview
    3.1.  Example JWE
4.  JWE Header
    4.1.  Reserved Header Parameter Names
    4.2.  Public Header Parameter Names
    4.3.  Private Header Parameter Names
5.  Message Encryption
6.  Message Decryption
7.  CEK Encryption
    7.1.  Asymmetric Encryption
    7.2.  Symmetric Encryption
8.  Composition
9.  Encrypting JWEs with Cryptographic Algorithms
    9.1.  Encrypting a JWE with TBD
    9.2.  Additional Algorithms
10.  IANA Considerations
11.  Security Considerations
    11.1.  Unicode Comparison Security Issues
12.  Open Issues and Things To Be Done (TBD)
13.  References
    13.1.  Normative References
    13.2.  Informative References
Appendix A.  JWE Examples
    A.1.  JWE Example using TBD Algorithm
        A.1.1.  Encrypting
        A.1.2.  Decrypting
Appendix B.  Algorithm Identifier Cross-Reference
Appendix C.  Acknowledgements
Appendix D.  Document History
§  Authors' Addresses




 TOC 

1.  Introduction

JSON Web Encryption (JWE) is a compact encryption format intended for space constrained environments such as HTTP Authorization headers and URI query parameters. It provides a wrapper for encrypted content using JSON RFC 4627 (Crockford, D., “The application/json Media Type for JavaScript Object Notation (JSON),” July 2006.) [RFC4627] data structures. The JWE encryption mechanisms are independent of the type of content being encrypted. A related signature capability is described in a separate JSON Web Signature (JWS) [JWS] (Jones, M., Balfanz, D., Bradley, J., Goland, Y., Panzer, J., Sakimura, N., and P. Tarjan, “JSON Web Signature (JWS),” October 2011.) specification.



 TOC 

2.  Terminology

JSON Web Encryption (JWE)
A data structure representing an encrypted version of a Plaintext. The structure consists of three parts: the JWE Header, the JWE Encrypted Key, and the JWE Ciphertext.
Plaintext
The bytes to be encrypted - a.k.a., the message.
Ciphertext
The encrypted version of the Plaintext.
Content Encryption Key (CEK)
A symmetric key generated to encrypt the Plaintext for the recipient to produce the Ciphertext, which is encrypted to the recipient as the JWE Encrypted Key.
JWE Header
A string containing a JSON object that describes the encryption operations applied to create the JWE Encrypted Key and the JWE Ciphertext.
JWE Encrypted Key
The Content Encryption Key (CEK) is encrypted with the intended recipient's key and the resulting encrypted content is recorded as a byte array, which is referred to as the JWE Encrypted Key.
JWE Ciphertext
A byte array containing the Ciphertext.
Encoded JWE Header
Base64url encoding of the bytes of the UTF-8 RFC 3629 (Yergeau, F., “UTF-8, a transformation format of ISO 10646,” November 2003.) [RFC3629] representation of the JWE Header.
Encoded JWE Encrypted Key
Base64url encoding of the JWE Encrypted Key.
Encoded JWE Ciphertext
Base64url encoding of the JWE Ciphertext.
Header Parameter Names
The names of the members within the JWE Header.
Header Parameter Values
The values of the members within the JWE Header.
Base64url Encoding
For the purposes of this specification, this term always refers to the URL- and filename-safe Base64 encoding described in RFC 4648 (Josefsson, S., “The Base16, Base32, and Base64 Data Encodings,” October 2006.) [RFC4648], Section 5, with the (non URL-safe) '=' padding characters omitted, as permitted by Section 3.2. (See Appendix C of [JWS] (Jones, M., Balfanz, D., Bradley, J., Goland, Y., Panzer, J., Sakimura, N., and P. Tarjan, “JSON Web Signature (JWS),” October 2011.) for notes on implementing base64url encoding without padding.)



 TOC 

3.  JSON Web Encryption (JWE) Overview

JWE represents encrypted content using JSON data structures and base64url encoding. The representation consists of three parts: the JWE Header, the JWE Encrypted Key, and the JWE Ciphertext. The three parts are base64url-encoded for transmission, and typically represented as the concatenation of the encoded strings in that order, with the three strings being separated by period ('.') characters, as is done when used in JSON Web Tokens (JWTs) [JWT] (Jones, M., Balfanz, D., Bradley, J., Goland, Y., Panzer, J., Sakimura, N., and P. Tarjan, “JSON Web Token (JWT),” October 2011.).

JWE utilizes encryption to ensure the confidentiality of the contents of the Plaintext. JWE does not add a content integrity check if not provided by the underlying encryption algorithm. If such a check is needed, an algorithm providing it such as AES-GCM [NIST‑800‑38D] (National Institute of Standards and Technology (NIST), “Recommendation for Block Cipher Modes of Operation: Galois/Counter Mode (GCM) and GMAC,” December 2001.) can be used, or alternatively, it can be provided through composition by encrypting a representation of the signed content.



 TOC 

3.1.  Example JWE

The following example JWE Header declares that:

{"alg":"RSA1_5",
 "enc":"A256GCM",
 "iv":"__79_Pv6-fg",
 "x5t":"7noOPq-hJ1_hCnvWh6IeYI2w9Q0"}

Base64url encoding the bytes of the UTF-8 representation of the JWE Header yields this Encoded JWE Header value:

TBD

TBD: Finish this example by showing generation of a Content Encryption Key (CEK), using the CEK to encrypt the Plaintext to produce the Ciphertext (and base64url encoding it), and using the recipient's key to encrypt the CEK to produce the JWE Encrypted Key (and base64url encoding it).



 TOC 

4.  JWE Header

The members of the JWE Header describe the encryption applied to the Plaintext. Implementations MUST understand the entire contents of the header; otherwise, the JWE MUST be rejected for processing.

The member names within the JWE Header are referred to as Header Parameter Names. These names MUST be unique. The corresponding values are referred to as Header Parameter Values.



 TOC 

4.1.  Reserved Header Parameter Names

The following header parameter names are reserved. All the names are short because a core goal of JWE is for the representations to be compact.

TBD: Describe the relationship between the JWS and JWE header parameters - especially the alg parameter, which can contain either signature algorithms (from JWS) or encryption algorithms (from JWE), and the key reference parameters jku, kid, x5u, and x5t.



Header Parameter NameJSON Value TypeHeader Parameter SyntaxHeader Parameter Semantics
alg string StringOrURI The alg (algorithm) header parameter identifies the cryptographic algorithm used to secure the JWE Encrypted Key. A list of reserved alg values is presented in Table 3 (JWE Reserved alg Parameter Values). The processing of the alg (algorithm) header parameter requires that the value of the alg header parameter MUST be one that is both supported and for which there exists a key for use with that algorithm associated with the intended recipient. The alg value is case sensitive. This header parameter is REQUIRED.
enc string StringOrURI The enc (encryption method) header parameter identifies the symmetric encryption algorithm used to secure the Ciphertext. A list of reserved enc values is presented in Table 4 (JWE Reserved enc Parameter Values). The processing of the enc (encryption method) header parameter requires that the value of the enc header parameter MUST be one that is supported. The enc value is case sensitive. This header parameter is REQUIRED.
iv string String Initialization Vector (iv) value for algorithms requiring it, represented as a base64url encoded string. This header parameter is OPTIONAL.
epk object JWK Key Object Ephemeral Public Key (epk) value created by the originator for the use in ECDH-ES RFC 6090 (McGrew, D., Igoe, K., and M. Salter, “Fundamental Elliptic Curve Cryptography Algorithms,” February 2011.) [RFC6090] encryption. This key is represented in the same manner as a JSON Web Key [JWK] (Jones, M., “JSON Web Key (JWK),” October 2011.) JWK Key Object value, containing curve, x, and y members. The inclusion of the JWK Key Object algorithm member is OPTIONAL. This header parameter is OPTIONAL.
zip string String Compression algorithm (zip) applied to the Plaintext before encryption, if any. This specification defines the value GZIP to refer to the encoding format produced by the file compression program "gzip" (GNU zip) as described in [RFC1952] (Deutsch, P., Gailly, J-L., Adler, M., Deutsch, L., and G. Randers-Pehrson, “GZIP file format specification version 4.3,” May 1996.); this format is a Lempel-Ziv coding (LZ77) with a 32 bit CRC. If no zip parameter is present, or its value is none, no compression is applied to the Plaintext before encryption. The zip value is case sensitive. This header parameter is OPTIONAL.
jku string URL The jku (JSON Web Key URL) header parameter is an absolute URL that refers to a resource for a set of JSON-encoded public keys, one of which corresponds to the key that was used to encrypt the JWE. The keys MUST be encoded as described in the JSON Web Key (JWK) [JWK] (Jones, M., “JSON Web Key (JWK),” October 2011.) specification. The protocol used to acquire the resource MUST provide integrity protection. An HTTP GET request to retrieve the certificate MUST use TLS RFC 2818 (Rescorla, E., “HTTP Over TLS,” May 2000.) [RFC2818] RFC 5246 (Dierks, T. and E. Rescorla, “The Transport Layer Security (TLS) Protocol Version 1.2,” August 2008.) [RFC5246] with server authentication RFC 6125 (Saint-Andre, P. and J. Hodges, “Representation and Verification of Domain-Based Application Service Identity within Internet Public Key Infrastructure Using X.509 (PKIX) Certificates in the Context of Transport Layer Security (TLS),” March 2011.) [RFC6125]. This header parameter is OPTIONAL.
kid string String The kid (key ID) header parameter is a hint indicating which key was used to encrypt the JWE. This allows originators to explicitly signal a change of key to recipients. The interpretation of the contents of the kid parameter is unspecified. This header parameter is OPTIONAL.
x5u string URL The x5u (X.509 URL) header parameter is an absolute URL that refers to a resource for the X.509 public key certificate or certificate chain corresponding to the key used to encrypt the JWE. The identified resource MUST provide a representation of the certificate or certificate chain that conforms to RFC 5280 (Cooper, D., Santesson, S., Farrell, S., Boeyen, S., Housley, R., and W. Polk, “Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) Profile,” May 2008.) [RFC5280] in PEM encoded form RFC 1421 (Linn, J., “Privacy Enhancement for Internet Electronic Mail: Part I: Message Encryption and Authentication Procedures,” February 1993.) [RFC1421]. The protocol used to acquire the resource MUST provide integrity protection. An HTTP GET request to retrieve the certificate MUST use TLS RFC 2818 (Rescorla, E., “HTTP Over TLS,” May 2000.) [RFC2818] RFC 5246 (Dierks, T. and E. Rescorla, “The Transport Layer Security (TLS) Protocol Version 1.2,” August 2008.) [RFC5246] with server authentication RFC 6125 (Saint-Andre, P. and J. Hodges, “Representation and Verification of Domain-Based Application Service Identity within Internet Public Key Infrastructure Using X.509 (PKIX) Certificates in the Context of Transport Layer Security (TLS),” March 2011.) [RFC6125]. This header parameter is OPTIONAL.
x5t string String The x5t (x.509 certificate thumbprint) header parameter provides a base64url encoded SHA-1 thumbprint (a.k.a. digest) of the DER encoding of the X.509 certificate that corresponds to the key that was used to encrypt the JWE. This header parameter is OPTIONAL.
typ string String The typ (type) header parameter is used to declare the type of the encrypted content. The typ value is case sensitive. This header parameter is OPTIONAL.

 Table 1: Reserved Header Parameter Definitions 

Additional reserved header parameter names MAY be defined via the IANA JSON Web Encryption Header Parameters registry, as per Section 10 (IANA Considerations). The syntax values used above are defined as follows:



Syntax NameSyntax Definition
String Any string value MAY be used.
StringOrURI Any string value MAY be used but a value containing a ":" character MUST be a URI as defined in RFC 3986 (Berners-Lee, T., Fielding, R., and L. Masinter, “Uniform Resource Identifier (URI): Generic Syntax,” January 2005.) [RFC3986].
URL A URL as defined in RFC 1738 (Berners-Lee, T., Masinter, L., and M. McCahill, “Uniform Resource Locators (URL),” December 1994.) [RFC1738].

 Table 2: Header Parameter Syntax Definitions 



 TOC 

4.2.  Public Header Parameter Names

Additional header parameter names can be defined by those using JWE. However, in order to prevent collisions, any new header parameter name or algorithm value SHOULD either be defined in the IANA JSON Web Encryption Header Parameters registry or be defined as a URI that contains a collision resistant namespace. In each case, the definer of the name or value MUST take reasonable precautions to make sure they are in control of the part of the namespace they use to define the header parameter name.

New header parameters should be introduced sparingly, as they can result in non-interoperable JWEs.



 TOC 

4.3.  Private Header Parameter Names

A producer and consumer of a JWE may agree to any header parameter name that is not a Reserved Name Section 4.1 (Reserved Header Parameter Names) or a Public Name Section 4.2 (Public Header Parameter Names). Unlike Public Names, these private names are subject to collision and should be used with caution.

New header parameters should be introduced sparingly, as they can result in non-interoperable JWEs.



 TOC 

5.  Message Encryption

The message encryption process is as follows:

  1. Generate a random Content Encryption Key (CEK). The CEK MUST have a length at least equal to that of the required encryption keys and MUST be generated randomly. See RFC 4086 (Eastlake, D., Schiller, J., and S. Crocker, “Randomness Requirements for Security,” June 2005.) [RFC4086] for considerations on generating random values.
  2. Encrypt the CEK for the recipient (see Section 7 (CEK Encryption)).
  3. Generate a random IV (if required for the algorithm).
  4. Compress the Plaintext if a zip parameter was included.
  5. Serialize the (compressed) Plaintext into a bitstring M.
  6. Encrypt M using the CEK and IV to form the bitstring C.
  7. Set the Encoded JWE Ciphertext equal to the base64url encoded representation of C.
  8. Create the JWE Header containing the encryption parameters used.
  9. Base64url encoded the UTF-8 representation of the JWE Header to create the Encoded JWE Header.
  10. The three encoded parts, taken together, are the result of the encryption.


 TOC 

6.  Message Decryption

The message decryption process is the reverse of the encryption process. If any of these steps fails, the JWE MUST be rejected.

  1. The Encoded JWE Header, the Encoded JWE Encrypted Key, and the Encoded JWE Ciphertext MUST be successfully base64url decoded following the restriction that no padding characters have been used.
  2. The resulting JWE Header MUST be completely valid JSON syntax conforming to RFC 4627 (Crockford, D., “The application/json Media Type for JavaScript Object Notation (JSON),” July 2006.) [RFC4627].
  3. The resulting JWE Header MUST be validated to only include parameters and values whose syntax and semantics are both understood and supported.
  4. Verify that the JWE Header appears to reference a key known to the recipient.
  5. Decrypt the JWE Encrypted Key to produce the CEK.
  6. Decrypt the binary representation of the JWE Ciphertext using the CEK.
  7. Uncompress the result of the previous step, if a zip parameter was included.
  8. Output the result.



 TOC 

7.  CEK Encryption

JWE supports two forms of CEK encryption:



 TOC 

7.1.  Asymmetric Encryption

In the asymmetric encryption mode, the CEK is encrypted under the recipient's public key. The asymmetric encryption modes defined for use with this in this specification are listed in in Table 3 (JWE Reserved alg Parameter Values).



 TOC 

7.2.  Symmetric Encryption

In the symmetric encryption mode, the CEK is encrypted under a symmetric key shared between the sender and receiver. The symmetric encryption modes defined for use with this in this specification are listed in in Table 3 (JWE Reserved alg Parameter Values). For GCM, the random 64-bit IV is prepended to the ciphertext.



 TOC 

8.  Composition

This document does not specify a combination signed and encrypted mode. However, because the contents of a message can be arbitrary, encryption and data origin authentication can be provided by recursively encapsulating multiple JWE and JWS messages. In general, senders SHOULD sign the message and then encrypt the result (thus encrypting the signature). This prevents attacks in which the signature is stripped, leaving just an encrypted message, as well as providing privacy for the signer.



 TOC 

9.  Encrypting JWEs with Cryptographic Algorithms

JWE uses cryptographic algorithms to encrypt the Content Encryption Key (CEK) and the Plaintext. This section specifies a set of specific algorithms for these purposes.

The table below Table 3 (JWE Reserved alg Parameter Values) is the set of alg header parameter values that are reserved by this specification. These algorithms are used to encrypt the CEK, which produces the JWE Encrypted Key.



alg Parameter ValueEncryption Algorithm
RSA1_5 RSA using RSA-PKCS1-1.5 padding, as defined in RFC 3447 (Jonsson, J. and B. Kaliski, “Public-Key Cryptography Standards (PKCS) #1: RSA Cryptography Specifications Version 2.1,” February 2003.) [RFC3447]
RSA-OAEP RSA using Optimal Asymmetric Encryption Padding (OAEP), as defined in RFC 3447 (Jonsson, J. and B. Kaliski, “Public-Key Cryptography Standards (PKCS) #1: RSA Cryptography Specifications Version 2.1,” February 2003.) [RFC3447]
ECDH-ES Elliptic Curve Diffie-Hellman Ephemeral Static, as defined in RFC 6090 (McGrew, D., Igoe, K., and M. Salter, “Fundamental Elliptic Curve Cryptography Algorithms,” February 2011.) [RFC6090], and using the Concat KDF, as defined in [NIST‑800‑56A] (National Institute of Standards and Technology (NIST), “Recommendation for Pair-Wise Key Establishment Schemes Using Discrete Logarithm Cryptography (Revised),” March 2007.), where the Digest Method is SHA-256
A128KW Advanced Encryption Standard (AES) Key Wrap Algorithm using 128 bit keys, as defined in RFC 3394 (Schaad, J. and R. Housley, “Advanced Encryption Standard (AES) Key Wrap Algorithm,” September 2002.) [RFC3394]
A256KW Advanced Encryption Standard (AES) Key Wrap Algorithm using 256 bit keys, as defined in RFC 3394 (Schaad, J. and R. Housley, “Advanced Encryption Standard (AES) Key Wrap Algorithm,” September 2002.) [RFC3394]
A128GCM Advanced Encryption Standard (AES) using 128 bit keys in Galois/Counter Mode, as defined in [FIPS‑197] (National Institute of Standards and Technology (NIST), “Advanced Encryption Standard (AES),” November 2001.) and [NIST‑800‑38D] (National Institute of Standards and Technology (NIST), “Recommendation for Block Cipher Modes of Operation: Galois/Counter Mode (GCM) and GMAC,” December 2001.)
A256GCM Advanced Encryption Standard (AES) using 256 bit keys in Galois/Counter Mode, as defined in [FIPS‑197] (National Institute of Standards and Technology (NIST), “Advanced Encryption Standard (AES),” November 2001.) and [NIST‑800‑38D] (National Institute of Standards and Technology (NIST), “Recommendation for Block Cipher Modes of Operation: Galois/Counter Mode (GCM) and GMAC,” December 2001.)

 Table 3: JWE Reserved alg Parameter Values 

The table below Table 4 (JWE Reserved enc Parameter Values) is the set of enc header parameter values that are reserved by this specification. These algorithms are used to encrypt the Plaintext, which produces the Ciphertext.



enc Parameter ValueSymmetric Encryption Algorithm
A128CBC Advanced Encryption Standard (AES) using 128 bit keys in Cipher Block Chaining mode, as defined in [FIPS‑197] (National Institute of Standards and Technology (NIST), “Advanced Encryption Standard (AES),” November 2001.) and [NIST‑800‑38A] (National Institute of Standards and Technology (NIST), “Recommendation for Block Cipher Modes of Operation,” December 2001.)
A256CBC Advanced Encryption Standard (AES) using 256 bit keys in Cipher Block Chaining mode, as defined in [FIPS‑197] (National Institute of Standards and Technology (NIST), “Advanced Encryption Standard (AES),” November 2001.) and [NIST‑800‑38A] (National Institute of Standards and Technology (NIST), “Recommendation for Block Cipher Modes of Operation,” December 2001.)
A128GCM Advanced Encryption Standard (AES) using 128 bit keys in Galois/Counter Mode, as defined in [FIPS‑197] (National Institute of Standards and Technology (NIST), “Advanced Encryption Standard (AES),” November 2001.) and [NIST‑800‑38D] (National Institute of Standards and Technology (NIST), “Recommendation for Block Cipher Modes of Operation: Galois/Counter Mode (GCM) and GMAC,” December 2001.)
A256GCM Advanced Encryption Standard (AES) using 256 bit keys in Galois/Counter Mode, as defined in [FIPS‑197] (National Institute of Standards and Technology (NIST), “Advanced Encryption Standard (AES),” November 2001.) and [NIST‑800‑38D] (National Institute of Standards and Technology (NIST), “Recommendation for Block Cipher Modes of Operation: Galois/Counter Mode (GCM) and GMAC,” December 2001.)

 Table 4: JWE Reserved enc Parameter Values 

Of these algorithms, only RSA-PKCS1-1.5 with 2048 bit keys, AES-128-CBC, and AES-256-CBC MUST be implemented by conforming implementations. It is RECOMMENDED that implementations also support ECDH-ES with 256 bit keys, AES-128-GCM, and AES-256-GCM. Support for other algorithms and key sizes is OPTIONAL.



 TOC 

9.1.  Encrypting a JWE with TBD

TBD: Descriptions of the particulars of each specified algorithm go here.



 TOC 

9.2.  Additional Algorithms

Additional algorithms MAY be used to protect JWEs with corresponding alg and enc header parameter values being defined to refer to them. New alg and enc header parameter values SHOULD either be defined in the IANA JSON Web Encryption Algorithms registry or be a URI that contains a collision resistant namespace. In particular, the use of algorithm identifiers defined in [W3C.REC‑xmlenc‑core‑20021210] (Eastlake, D. and J. Reagle, “XML Encryption Syntax and Processing,” December 2002.), [W3C.CR‑xmlenc‑core1‑20110303] (Hirsch, F., Reagle, J., Eastlake, D., and T. Roessler, “XML Encryption Syntax and Processing Version 1.1,” March 2011.), and related specifications is permitted.



 TOC 

10.  IANA Considerations

This specification calls for:



 TOC 

11.  Security Considerations

TBD: Lots of work to do here. We need to remember to look into any issues relating to security and JSON parsing. One wonders just how secure most JSON parsing libraries are. Were they ever hardened for security scenarios? If not, what kind of holes does that open up? Also, we need to walk through the JSON standard and see what kind of issues we have especially around comparison of names. For instance, comparisons of header parameter names and other parameters must occur after they are unescaped. Need to also put in text about: Importance of keeping secrets secret. Rotating keys. Strengths and weaknesses of the different algorithms.

TBD: Need to put in text about why strict JSON validation is necessary. Basically, that if malformed JSON is received then the intent of the sender is impossible to reliably discern. One example of malformed JSON that MUST be rejected is an object in which the same member name occurs multiple times.

TBD: We need a section on generating randomness in browsers - it's easy to screw up.

When utilizing TLS to retrieve information, the authority providing the resource MUST be authenticated and the information retrieved MUST be free from modification.



 TOC 

11.1.  Unicode Comparison Security Issues

Header parameter names in JWEs are Unicode strings. For security reasons, the representations of these names must be compared verbatim after performing any escape processing (as per RFC 4627 (Crockford, D., “The application/json Media Type for JavaScript Object Notation (JSON),” July 2006.) [RFC4627], Section 2.5).

This means, for instance, that these JSON strings must compare as being equal ("enc", "\u0065nc"), whereas these must all compare as being not equal to the first set or to each other ("ENC", "Enc", "en\u0043").

JSON strings MAY contain characters outside the Unicode Basic Multilingual Plane. For instance, the G clef character (U+1D11E) may be represented in a JSON string as "\uD834\uDD1E". Ideally, JWE implementations SHOULD ensure that characters outside the Basic Multilingual Plane are preserved and compared correctly; alternatively, if this is not possible due to these characters exercising limitations present in the underlying JSON implementation, then input containing them MUST be rejected.



 TOC 

12.  Open Issues and Things To Be Done (TBD)

The following items remain to be done in this draft:



 TOC 

13.  References



 TOC 

13.1. Normative References

[FIPS-197] National Institute of Standards and Technology (NIST), “Advanced Encryption Standard (AES),” FIPS PUB 197, November 2001.
[JWK] Jones, M., “JSON Web Key (JWK),” October 2011.
[JWS] Jones, M., Balfanz, D., Bradley, J., Goland, Y., Panzer, J., Sakimura, N., and P. Tarjan, “JSON Web Signature (JWS),” October 2011.
[NIST-800-38A] National Institute of Standards and Technology (NIST), “Recommendation for Block Cipher Modes of Operation,” NIST PUB 800-38A, December 2001.
[NIST-800-38D] National Institute of Standards and Technology (NIST), “Recommendation for Block Cipher Modes of Operation: Galois/Counter Mode (GCM) and GMAC,” NIST PUB 800-38D, December 2001.
[NIST-800-56A] National Institute of Standards and Technology (NIST), “Recommendation for Pair-Wise Key Establishment Schemes Using Discrete Logarithm Cryptography (Revised),” NIST PUB 800-56A, March 2007.
[RFC1421] Linn, J., “Privacy Enhancement for Internet Electronic Mail: Part I: Message Encryption and Authentication Procedures,” RFC 1421, February 1993 (TXT).
[RFC1738] Berners-Lee, T., Masinter, L., and M. McCahill, “Uniform Resource Locators (URL),” RFC 1738, December 1994 (TXT).
[RFC1952] Deutsch, P., Gailly, J-L., Adler, M., Deutsch, L., and G. Randers-Pehrson, “GZIP file format specification version 4.3,” RFC 1952, May 1996 (TXT, PS, PDF).
[RFC2119] Bradner, S., “Key words for use in RFCs to Indicate Requirement Levels,” BCP 14, RFC 2119, March 1997 (TXT, HTML, XML).
[RFC2818] Rescorla, E., “HTTP Over TLS,” RFC 2818, May 2000 (TXT).
[RFC3394] Schaad, J. and R. Housley, “Advanced Encryption Standard (AES) Key Wrap Algorithm,” RFC 3394, September 2002 (TXT).
[RFC3447] Jonsson, J. and B. Kaliski, “Public-Key Cryptography Standards (PKCS) #1: RSA Cryptography Specifications Version 2.1,” RFC 3447, February 2003 (TXT).
[RFC3629] Yergeau, F., “UTF-8, a transformation format of ISO 10646,” STD 63, RFC 3629, November 2003 (TXT).
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, “Uniform Resource Identifier (URI): Generic Syntax,” STD 66, RFC 3986, January 2005 (TXT, HTML, XML).
[RFC4086] Eastlake, D., Schiller, J., and S. Crocker, “Randomness Requirements for Security,” BCP 106, RFC 4086, June 2005 (TXT).
[RFC4627] Crockford, D., “The application/json Media Type for JavaScript Object Notation (JSON),” RFC 4627, July 2006 (TXT).
[RFC4648] Josefsson, S., “The Base16, Base32, and Base64 Data Encodings,” RFC 4648, October 2006 (TXT).
[RFC5226] Narten, T. and H. Alvestrand, “Guidelines for Writing an IANA Considerations Section in RFCs,” BCP 26, RFC 5226, May 2008 (TXT).
[RFC5246] Dierks, T. and E. Rescorla, “The Transport Layer Security (TLS) Protocol Version 1.2,” RFC 5246, August 2008 (TXT).
[RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S., Housley, R., and W. Polk, “Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) Profile,” RFC 5280, May 2008 (TXT).
[RFC5785] Nottingham, M. and E. Hammer-Lahav, “Defining Well-Known Uniform Resource Identifiers (URIs),” RFC 5785, April 2010 (TXT).
[RFC6090] McGrew, D., Igoe, K., and M. Salter, “Fundamental Elliptic Curve Cryptography Algorithms,” RFC 6090, February 2011 (TXT).
[RFC6125] Saint-Andre, P. and J. Hodges, “Representation and Verification of Domain-Based Application Service Identity within Internet Public Key Infrastructure Using X.509 (PKIX) Certificates in the Context of Transport Layer Security (TLS),” RFC 6125, March 2011 (TXT).


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13.2. Informative References

[I-D.rescorla-jsms] Rescorla, E. and J. Hildebrand, “JavaScript Message Security Format,” draft-rescorla-jsms-00 (work in progress), March 2011 (TXT).
[JCA] Oracle, “Java Cryptography Architecture,” 2011.
[JSS] Bradley, J. and N. Sakimura (editor), “JSON Simple Sign,” September 2010.
[JWT] Jones, M., Balfanz, D., Bradley, J., Goland, Y., Panzer, J., Sakimura, N., and P. Tarjan, “JSON Web Token (JWT),” October 2011.
[RFC3275] Eastlake, D., Reagle, J., and D. Solo, “(Extensible Markup Language) XML-Signature Syntax and Processing,” RFC 3275, March 2002 (TXT).
[RFC5652] Housley, R., “Cryptographic Message Syntax (CMS),” STD 70, RFC 5652, September 2009 (TXT).
[W3C.CR-xmlenc-core1-20110303] Hirsch, F., Reagle, J., Eastlake, D., and T. Roessler, “XML Encryption Syntax and Processing Version 1.1,” World Wide Web Consortium CR CR-xmlenc-core1-20110303, March 2011 (HTML).
[W3C.REC-xmlenc-core-20021210] Eastlake, D. and J. Reagle, “XML Encryption Syntax and Processing,” World Wide Web Consortium Recommendation REC-xmlenc-core-20021210, December 2002 (HTML).


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Appendix A.  JWE Examples

This section provides several examples of JWEs.



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A.1.  JWE Example using TBD Algorithm



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A.1.1.  Encrypting

TBD: Demonstrate encryption steps with this algorithm



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A.1.2.  Decrypting

TBD: Demonstrate decryption steps with this algorithm



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Appendix B.  Algorithm Identifier Cross-Reference

This appendix contains a table cross-referencing the alg and enc values used in this specification with the equivalent identifiers used by other standards and software packages. See XML DSIG (Eastlake, D., Reagle, J., and D. Solo, “(Extensible Markup Language) XML-Signature Syntax and Processing,” March 2002.) [RFC3275] and Java Cryptography Architecture (Oracle, “Java Cryptography Architecture,” 2011.) [JCA] for more information about the names defined by those documents.



AlgorithmJWEXML ENCJCAOID
RSA using RSA-PKCS1-1.5 padding RSA1_5 http://www.w3.org/2001/04/xmlenc#rsa-1_5 RSA/ECB/PKCS1Padding TBD
RSA using Optimal Asymmetric Encryption Padding (OAEP) RSA-OAEP http://www.w3.org/2001/04/xmlenc#rsa-oaep-mgf1p RSA/ECB/OAEPWithSHA-1AndMGF1Padding TBD
Elliptic Curve Diffie-Hellman Ephemeral Static ECDH-ES http://www.w3.org/2009/xmlenc11#ECDH-ES TBD TBD
Advanced Encryption Standard (AES) Key Wrap Algorithm RFC 3394 (Schaad, J. and R. Housley, “Advanced Encryption Standard (AES) Key Wrap Algorithm,” September 2002.) [RFC3394] using 128 bit keys A128KW http://www.w3.org/2001/04/xmlenc#kw-aes128 TBD TBD
Advanced Encryption Standard (AES) Key Wrap Algorithm RFC 3394 (Schaad, J. and R. Housley, “Advanced Encryption Standard (AES) Key Wrap Algorithm,” September 2002.) [RFC3394] using 256 bit keys A256KW http://www.w3.org/2001/04/xmlenc#kw-aes256 TBD TBD
Advanced Encryption Standard (AES) using 128 bit keys in Cipher Block Chaining mode A128CBC http://www.w3.org/2001/04/xmlenc#aes128-cbc AES/CBC/PKCS5Padding TBD
Advanced Encryption Standard (AES) using 256 bit keys in Cipher Block Chaining mode A256CBC http://www.w3.org/2001/04/xmlenc#aes256-cbc AES/CBC/PKCS5Padding TBD
Advanced Encryption Standard (AES) using 128 bit keys in Galois/Counter Mode A128GCM http://www.w3.org/2009/xmlenc11#aes128-gcm AES/GCM/NoPadding TBD
Advanced Encryption Standard (AES) using 256 bit keys in Galois/Counter Mode A256GCM http://www.w3.org/2009/xmlenc11#aes256-gcm AES/GCM/NoPadding TBD

 Table 5: Algorithm Identifier Cross-Reference 



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Appendix C.  Acknowledgements

Solutions for encrypting JSON content were also explored by [JSS] (Bradley, J. and N. Sakimura (editor), “JSON Simple Sign,” September 2010.) and [I‑D.rescorla‑jsms] (Rescorla, E. and J. Hildebrand, “JavaScript Message Security Format,” March 2011.), both of which significantly influenced this draft. This draft attempts to explicitly reuse as much from [W3C.CR‑xmlenc‑core1‑20110303] (Hirsch, F., Reagle, J., Eastlake, D., and T. Roessler, “XML Encryption Syntax and Processing Version 1.1,” March 2011.) and RFC 5652 (Housley, R., “Cryptographic Message Syntax (CMS),” September 2009.) [RFC5652] as possible, while utilizing simple compact JSON-based data structures.

Special thanks are due to John Bradley and Nat Sakimura for the discussions that helped inform the content of this specification and to Eric Rescorla and Joe Hildebrand for allowing the reuse of some of the text from [I‑D.rescorla‑jsms] (Rescorla, E. and J. Hildebrand, “JavaScript Message Security Format,” March 2011.) in this document.



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Appendix D.  Document History

-01

-00



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Authors' Addresses

  Michael B. Jones
  Microsoft
Email:  mbj@microsoft.com
URI:  http://self-issued.info/
  
  Eric Rescorla
  RTFM, Inc.
Email:  ekr@rtfm.com
  
  Joe Hildebrand
  Cisco Systems, Inc.
Email:  jhildebr@cisco.com