JSON Web Signature JSON Serialization (JWS-JS)
draft-jones-json-web-signature-json-serialization-02

Abstract

The JSON Web Signature JSON Serialization (JWS-JS) is a means of representing content secured with digital signatures or Hash-based Message Authentication Codes (HMACs) using JavaScript Object Notation (JSON) data structures. This specification describes a means of representing secured content as a JSON data object (as opposed to the JWS specification, which uses a compact serialization with a URL-safe representation). It enables multiple digital signatures and/or HMACs to be applied to the same content (unlike JWS). Cryptographic algorithms and identifiers used with this specification are described in the separate JSON Web Algorithms (JWA) specification. The JSON Serialization for related encryption functionality is described in the separate JSON Web Encryption JSON Serialization (JWE-JS) specification.

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Table of Contents

1.  Introduction
    1.1.  Notational Conventions
2.  Terminology
3.  JSON Serialization
4.  Example JWS-JS
5.  IANA Considerations
6.  Security Considerations
7.  Open Issues
8.  References
    8.1.  Normative References
    8.2.  Informative References
Appendix A.  Acknowledgements
Appendix B.  Document History
§  Authors' Addresses

1.  Introduction

The JSON Web Signature JSON Serialization (JWS-JS) is a format for representing content secured with digital signatures or Hash-based Message Authentication Codes (HMACs) as a JavaScript Object Notation (JSON) [RFC4627] (Crockford, D., “The application/json Media Type for JavaScript Object Notation (JSON),” July 2006.) object. It enables multiple digital signatures and/or HMACs to be applied to the same content (unlike JWS [JWS] (Jones, M., Bradley, J., and N. Sakimura, “JSON Web Signature (JWS),” July 2012.)). The digital signature and HMAC mechanisms used are independent of the type of content being secured, allowing arbitrary content to be secured. Cryptographic algorithms and identifiers used with this specification are described in the separate JSON Web Algorithms (JWA) [JWA] (Jones, M., “JSON Web Algorithms (JWA),” July 2012.) specification. The JSON Serialization for related encryption functionality is described in the separate JSON Web Encryption JSON Serialization (JWE-JS) [JWE‑JS] (Jones, M., “JSON Web Encryption JSON Serialization (JWE-JS),” July 2012.) specification.

1.1.  Notational Conventions

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 Key words for use in RFCs to Indicate Requirement Levels [RFC2119] (Bradner, S., “Key words for use in RFCs to Indicate Requirement Levels,” March 1997.).

2.  Terminology

This specification uses the same terminology as the JSON Web Signature (JWS) [JWS] (Jones, M., Bradley, J., and N. Sakimura, “JSON Web Signature (JWS),” July 2012.) specification.

3.  JSON Serialization

The JSON Serialization represents secured content as a JSON object with members for each of three constituent parts: a headers member whose value is a non-empty array of Encoded JWS Header values, a payload member whose value is an Encoded JWS Payload value, and a signatures member whose value is a non-empty array of Encoded JWS Signature values, where the number of elements in both arrays is the same.

Unlike the compact serialization used by JWSs, content using the JSON Serialization MAY be secured with more than one digital signature and/or HMAC value. Each is represented as an Encoded JWS Signature in the signatures member array. For each, there is a corresponding headers member array element that is an Encoded JWS Header specifying the digital signature or HMAC applied to the Encoded JWS Header value and the Encoded JWS Payload value to create the JWS Signature value. Therefore, the syntax is:

{"headers":["<header 1 contents>",...,"<header N contents>"],
 "payload":"<payload contents>",
 "signatures":["<signature 1 contents>",...,"<signature N contents>"]
}

The contents of the Encoded JWS Header, Encoded JWS Payload, and Encoded JWS Signature values are exactly as specified in JSON Web Signature (JWS) [JWS] (Jones, M., Bradley, J., and N. Sakimura, “JSON Web Signature (JWS),” July 2012.). They are interpreted and validated in the same manner, with each corresponding headers and signatures value being created or validated together. The arrays MUST have the same number of elements.

The i'th JWS Signature value is computed on the JWS Secured Input corresponding to the concatenation of the i'th Encoded JWS Header, a period ('.') character, and the Encoded JWS Payload in the same manner described in the JWS specification. This has the desirable result that each Encoded JWS signature value in the signatures array is identical to the value that would be used for the same header and payload in a JWS.

4.  Example JWS-JS

This section contains an example using the JWS JSON Serialization. This example demonstrates the capability for conveying multiple digital signatures and/or HMACs for the same payload.

The Encoded JWS Payload used in this example is the same as used in the examples in Appendix A of JWS (with line breaks for display purposes only):

eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFt
cGxlLmNvbS9pc19yb290Ijp0cnVlfQ

Two digital signatures are used in this example: an RSA SHA-256 signature, for which the header and signature values are the same as in Appendix A.2 of JWS, and an ECDSA P-256 SHA-256 signature, for which the header and signature values are the same as in Appendix A.3 of JWS. The two Decoded JWS Header Segments used are:

{"alg":"RS256"}

and:

{"alg":"ES256"}

Since the computations of the JWS Header and JWS Signature values are the same as in Appendix A.2 and Appendix A.3 of JWS, they are not repeated here.

The complete JSON Web Signature JSON Serialization (JWS-JS) for these values is as follows (with line breaks for display purposes only):

{"headers":[
  "eyJhbGciOiJSUzI1NiJ9",
  "eyJhbGciOiJFUzI1NiJ9"],
 "payload":"eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0
dHA6Ly9leGFtcGxlLmNvbS9pc19yb290Ijp0cnVlfQ",
 "signatures":[
  "cC4hiUPoj9Eetdgtv3hF80EGrhuB__dzERat0XF9g2VtQgr9PJbu3XOiZj5RZ
mh7AAuHIm4Bh-0Qc_lF5YKt_O8W2Fp5jujGbds9uJdbF9CUAr7t1dnZcAcQjbKBY
NX4BAynRFdiuB--f_nZLgrnbyTyWzO75vRK5h6xBArLIARNPvkSjtQBMHlb1L07Q
e7K0GarZRmB_eSN9383LcOLn6_dO--xi12jzDwusC-eOkHWEsqtFZESc6BfI7noO
PqvhJ1phCnvWh6IeYI2w9QOYEUipUTI8np6LbgGY9Fs98rqVt5AXLIhWkWywlVmt
VrBp0igcN_IoypGlUPQGe77Rw",
  "DtEhU3ljbEg8L38VWAfUAqOyKAM6-Xx-F4GawxaepmXFCgfTjDxw5djxLa8IS
lSApmWQxfKTUJqPP3-Kg6NU1Q"]
}

5.  IANA Considerations

This specification makes no requests of IANA.

6.  Security Considerations

The security considerations for this specification are the same as those for the JSON Web Signature (JWS) [JWS] (Jones, M., Bradley, J., and N. Sakimura, “JSON Web Signature (JWS),” July 2012.) specification.

7.  Open Issues

[[ to be removed by the RFC editor before publication as an RFC ]]

The following items remain to be considered or done in this draft:

• Track changes that occur in the JWS spec.

8.  References

8.1. Normative References

8.2. Informative References

Appendix A.  Acknowledgements

JSON serializations for secured content were previously explored by Magic Signatures (Panzer (editor), J., Laurie, B., and D. Balfanz, “Magic Signatures,” January 2011.) [MagicSignatures] and JSON Simple Sign (Bradley, J. and N. Sakimura (editor), “JSON Simple Sign,” September 2010.) [JSS].

Appendix B.  Document History

[[ to be removed by the RFC editor before publication as an RFC ]]

-02

• Tracked editorial changes made to the JWS spec.

-01

• Corrected the Magic Signatures reference.

-00

• Created the initial version incorporating JOSE working group input and drawing from the JSON Serialization previously proposed in draft-jones-json-web-token-01.

Authors' Addresses