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The JSON Private Key specification extends the JSON Web Key (JWK) and JSON Web Algorithms (JWA) specifications to define a JavaScript Object Notation (JSON) representation of private keys.
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1.
Introduction
1.1.
Notational Conventions
2.
Terminology
3.
JWK Parameters for Private Keys
3.1.
JWK Parameters for Elliptic Curve Private Keys
3.1.1.
"d" (ECC Private Key) Parameter
3.2.
JWK Parameters for RSA Private Keys
3.2.1.
"d" (Private Exponent) Parameter
3.2.2.
"p" (First Prime Factor) Parameter
3.2.3.
"q" (Second Prime Factor) Parameter
3.2.4.
"dp" (First Factor CRT Exponent) Parameter
3.2.5.
"dq" (Second Factor CRT Exponent) Parameter
3.2.6.
"qi" (First CRT Coefficient) Parameter
3.2.7.
"oth" (Other Primes Info) Parameter
3.2.7.1.
"r" (Prime Factor)
3.2.7.2.
"d" (Factor CRT Exponent)
3.2.7.3.
"t" (Factor CRT Coefficient)
4.
Example Private Keys
5.
IANA Considerations
5.1.
JSON Web Key Parameters Registration
5.1.1.
Registry Contents
6.
Security Considerations
7.
Normative References
Appendix A.
Document History
§
Author's Address
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The JSON Private Key specification extends the JSON Web Key (JWK) [JWK] (Jones, M., “JSON Web Key (JWK),” November 2012.) and JSON Web Algorithms (JWA) [JWA] (Jones, M., “JSON Web Algorithms (JWA),” November 2012.) specifications to define a JavaScript Object Notation (JSON) [RFC4627] (Crockford, D., “The application/json Media Type for JavaScript Object Notation (JSON),” July 2006.) representation of private keys.
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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.).
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This specification uses the same terminology as the JSON Web Key (JWK) [JWK] (Jones, M., “JSON Web Key (JWK),” November 2012.) and JSON Web Algorithms (JWA) [JWA] (Jones, M., “JSON Web Algorithms (JWA),” November 2012.) specifications.
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This section defines additional JSON Web Key parameters that enable JWKs to represent private keys.
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When the JWK alg member value is EC, the following member MAY be used to represent an Elliptic Curve private key:
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The d (ECC private key) member contains the Elliptic Curve private key value. It is represented as the base64url encoding of the value's unsigned big endian representation as a byte array. The array representation MUST not be shortened to omit any leading zero bytes. For instance, when representing 521 bit integers, the byte array to be base64url encoded MUST contain 66 bytes, including any leading zero bytes.
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When the JWK alg member value is RSA, the following member MAY be used to represent an RSA private key:
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The d (private exponent) member contains the private exponent value for the RSA private key. It is represented as the base64url encoding of the value's unsigned big endian representation as a byte array. The array representation MUST not be shortened to omit any leading zero bytes. For instance, when representing 2048 bit integers, the byte array to be base64url encoded MUST contain 256 bytes, including any leading zero bytes.
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The p (first prime factor) member contains the first prime factor, a positive integer. It is represented as the base64url encoding of the value's unsigned big endian representation as a byte array.
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The q (second prime factor) member contains the second prime factor, a positive integer. It is represented as the base64url encoding of the value's unsigned big endian representation as a byte array.
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The dp (first factor CRT exponent) member contains the Chinese Remainder Theorem (CRT) exponent of the first factor, a positive integer. It is represented as the base64url encoding of the value's unsigned big endian representation as a byte array.
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The dq (second factor CRT exponent) member contains the Chinese Remainder Theorem (CRT) exponent of the second factor, a positive integer. It is represented as the base64url encoding of the value's unsigned big endian representation as a byte array.
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The dp (first CRT coefficient) member contains the Chinese Remainder Theorem (CRT) coefficient of the second factor, a positive integer. It is represented as the base64url encoding of the value's unsigned big endian representation as a byte array.
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The oth (other primes info) member contains an array of information about any third and subsequent primes, should they exist. When only two primes have been used (the normal case), this parameter MUST be omitted. When three or more primes have been used, the number of array elements MUST be the number of primes used minus two. Each array element MUST be an object with the following members:
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The r (prime factor) parameter within an oth array member represents the value of a subsequent prime factor, a positive integer. It is represented as the base64url encoding of the value's unsigned big endian representation as a byte array.
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The d (Factor CRT Exponent) parameter within an oth array member represents the CRT exponent of the corresponding prime factor, a positive integer. It is represented as the base64url encoding of the value's unsigned big endian representation as a byte array.
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The t (factor CRT coefficient) parameter within an oth array member represents the CRT coefficient of the corresponding prime factor, a positive integer. It is represented as the base64url encoding of the value's unsigned big endian representation as a byte array.
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The following example JWK Set contains two keys represented as JWKs containing both public and private key values: one using an Elliptic Curve algorithm and a second one using an RSA algorithm. This example extends the example in Section 3 of [JWK] (Jones, M., “JSON Web Key (JWK),” November 2012.), adding private key values. (Line breaks are for display purposes only.)
{"keys": [ {"alg":"EC", "crv":"P256", "x":"MKBCTNIcKUSDii11ySs3526iDZ8AiTo7Tu6KPAqv7D4", "y":"4Etl6SRW2YiLUrN5vfvVHuhp7x8PxltmWWlbbM4IFyM", "d":"870MB6gfuTJ4HtUnUvYMyJpr5eUZNP4Bk43bVdj3eAE", "use":"enc", "kid":"1"}, {"alg":"RSA", "n":"0vx7agoebGcQSuuPiLJXZptN9nndrQmbXEps2aiAFbWhM78LhWx4 cbbfAAtVT86zwu1RK7aPFFxuhDR1L6tSoc_BJECPebWKRXjBZCiFV4n3oknjhMst n64tZ_2W5JsGY4Hc5n9yBXArwl93lqt7_RN5w6Cf0h4QyQ5v65YGjQR0_FDW2Q vzqY368QQMicAtaSqzs8KJZgnYb9c7d0zgdAZHzu6qMQvRL5hajrn1n91CbOpbIS D08qNLyrdktbFTWhAI4vMQFh6WeZu0fM4lFd2NcRwr3XPksINHaQG_xBniIqbw 0Ls1jF44csFCurkEgU8awapJzKnqDKgw", "e":"AQAB", "d":"X4cTteJY_gn4FYPsXB8rdXix5vwsg1FLN5E3EaG6RJoVHHLLKD9 M7dx5oo7GURknchnrRweUkC7hT5fJLM0WbFAKNLWY2vv7B6NqXSzUvxT0_YSfqij wp3RTzlBaCxWp4doFk5N2o8Gy_nHNKroADIkJ46pRUohsXywbReAdYaMwFs9tv8d _cPVY3i07a3t8MN6TNwm0dSawm9v47UiCl3Sk5ZiG7xojPLu4sbg1U2jx4IBTNBz nbJSzFHK66jT8bgkuqsk0GjskDJk19Z4qwjwbsnn4j2WBii3RLUs2lGVkY8fkFz me1z0HbIkfz0Y6mqnOYtqc0X4jfcKoAC8Q", "p":"83i7IvMGXoMXCskv73TKr8637FiO7Z27zv8oj6pbWUQyLPQBQxtPV nwD20R60eTDmD2ujnMt5PoqMrm8RfmNhVWDtjjMmCMjOpSXicFHj7XOuVIYQyqV WlWEh6dN36GVZYk93N8Bc9vY41xy8B9RzzOGVQzXvNEvn7O0nVbfs", "q":"3dfOR9cuYq0SmkFLzgItgMEfFzB2q3hWehMuG0oCuqnb3vobLyum qjVZQO1dIrdwgTnCdpYzBcOfW5r370AFXjiWft_NGEiovonizhKpo9VVS78TzFgx kIdrecRezsZ1kYd_s1qDbxtkDEgfAITAG9LUnADun4vIcb6yelxk", "dp":"G4sPXkc6Ya9y8oJW9_ILj4xuppu0lzi_H7VTkS8xj5SdX3coE0oim YwxIi2emTAue0UOa5dpgFGyBJ4c8tQ2VF402XRugKDTP8akYhFo5tAA77Qe_Nmtu YZc3C3m3I24G2GvR5sSDxUyAN2zq8Lfn9EUms6rY3Ob8YeiKkTiBj0", "dq":"s9lAH9fggBsoFR8Oac2R_E2gw282rT2kGOAhvIllETE1efrA6huUU vMfBcMpn8lqeW6vzznYY5SSQF7pMdC_agI3nG8Ibp1BUb0JUiraRNqUfLhcQb_d9 GF4Dh7e74WbRsobRonujTYN1xCaP6TO61jvWrXL18txXw494Q_cgk", "qi":"GyM_p6JrXySiz1toFgKbWVJdI3jQ4ypu9rbMWx3rQJBfmt0FoYzg UIZEVFEcOqwemRN81zoDAaaBk0KWNGDjJHZDdDmFhW3AN7lIpuxk_mHZGJ11rx yR8O55XLSe3SPmRfKwZI6yU24ZxvQKFYItdldUKGzO6Ia6zTKhAVRU", "kid":"20110429"} ] }
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This specification registers the parameter names defined in Section 3.1 (JWK Parameters for Elliptic Curve Private Keys) and Section 3.2 (JWK Parameters for RSA Private Keys) in the IANA JSON Web Key Parameters registry [JWK] (Jones, M., “JSON Web Key (JWK),” November 2012.).
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The security considerations for this specification are the same as those for the JSON Web Key (JWK) [JWK] (Jones, M., “JSON Web Key (JWK),” November 2012.) specification and the portion of the JSON Web Algorithms (JWA) [JWA] (Jones, M., “JSON Web Algorithms (JWA),” November 2012.) specification that pertains to key representations.
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[JWA]  Jones, M., “JSON Web Algorithms (JWA),” November 2012. 
[JWK]  Jones, M., “JSON Web Key (JWK),” November 2012. 
[RFC2119]  Bradner, S., “Key words for use in RFCs to Indicate Requirement Levels,” BCP 14, RFC 2119, March 1997 (TXT, HTML, XML). 
[RFC4627]  Crockford, D., “The application/json Media Type for JavaScript Object Notation (JSON),” RFC 4627, July 2006 (TXT). 
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[[ to be removed by the RFC editor before publication as an RFC ]]
01
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Michael B. Jones  
Microsoft  
Email:  mbj@microsoft.com 
URI:  http://selfissued.info/ 