Re: [jose] TTL for JWK

"Manger, James H" <> Wed, 20 February 2013 12:27 UTC

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From: "Manger, James H" <>
To: Brian Campbell <>, "" <>
Date: Wed, 20 Feb 2013 23:27:29 +1100
Thread-Topic: [jose] TTL for JWK
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Subject: Re: [jose] TTL for JWK
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This feature sounds so close in function to an HTTP Cache-Control header. Surely we can just use this existing mechanism? Particularly as the real use case mentioned in getting a JWK from an HTTPS URI.

P.S. If we do defer specifying “TTL for JWK” now, but after a few years experience of rolling keys in OpenID Connect decide it would be good, then I wonder how awkward deploying it would be due to the MUST-understand-everything rule?

James Manger

On 2013-02-19, at 9:26 PM, Brian Campbell <<>> wrote:

…this was more of a indicator about how long a key could be cached/used with a reasonable expectation that things would still work…
From:<> [<>] On Behalf Of Brian Campbell
Sent: Tuesday, February 19, 2013 3:43 PM
Subject: [jose] TTL for JWK
I'd like to float the idea of introducing a time to live parameter to the base JWK document, which could probably fit in as a subsection of §4 that defines parameters common to all key types [1].

The motivation is that many uses of JWKs will involve caching of JWK data and a TTL parameter could be used to indicate how long a key could be safely cached and used without needing to recheck the JWK source. I don't want it to be a hard expiration date for the key but rather a hint to help facility efficient and error free caching.

OpenID Connect has a real use case for this where entities publish their keys via a JWK Set at an HTTPS URL. To support key rotation and encryption, there needs to be some way to indicate the TTL of a public key used to encrypt. Of course, this isn't the only way to skin that cat but it strikes me as a good way and one that might provide utility for JWK in other contexts.
JSON Web Token [2] defines a data type that is "A JSON numeric value representing the number of seconds from 1970-01-01T0:0:0Z UTC until the specified UTC date/time" that seems like it could be co-opted to work well as the value for a "ttl" parameter.