Re: [jose] The role of JWK

[Sergey Beryozkin <[e-mail]>]

Hi Richard and Justin

Very helpful, many thanks !

Richard: thanks for the link, the idea of using JWK as a standard medium 
for shipping the key (information) is something that helps to understand 
why JWK is referred to so much in the specifications like JWE/JWS

Justin: I'll try my best not to copy the Java code you linked too :-).

Thanks for links to the examples, let me ask few questions below:

On 14/08/14 16:04, Justin Richer wrote:
> Services are starting to publish their public keys as JWK instead of
> X509, since a JWK doesn't require a trusted CA and can be much more
> easily rotated at runtime.
Sorry if it is off-topic, is JWK representing a public key (the public 
exponent) is effectively a self-signed public key/cert ? What provides 
the extra trust into such JWK ? I've heard here about JWK Thumbprints ?

> This is the class from our OAuth/OpenID
> Connect system that builds signers and validators off of a public-key
> JWK (using the Nimbus-DS JOSE library):
>
>     https://github.com/mitreid-connect/OpenID-Connect-Java-Spring-Server/blob/master/openid-connect-common/src/main/java/org/mitre/jwt/signer/service/impl/JWKSetCacheService.java
>
>
> To add to that, with the private/shared key components of JWK, it can be
> a very effective key store. Our OAuth server uses this for its keys,
> this is the class that reads the file and makes the keys available as
> Java key objects to the rest of the system:
>
>     https://github.com/mitreid-connect/OpenID-Connect-Java-Spring-Server/blob/master/openid-connect-common/src/main/java/org/mitre/jose/keystore/JWKSetKeyStore.java
>
> As you can see, these are both exceedingly simple classes because they
> simple read the URL (in the first case) or file (in the second case) and
> parse the JSON found there into a JWK set, which is then used to create
> the bare keys in the Java security framework. This is the RSA public key
> parser for example:
>
>     https://bitbucket.org/connect2id/nimbus-jose-jwt/src/0d5b12b4d4b84c822bec4af368b3bea5120cb310/src/main/java/com/nimbusds/jose/jwk/RSAKey.java?at=master#cl-1395
>
>
> Finally, in order to make these keys more easy to deal with, we wrote a
> simple key generator program that will spin up a new RSA, EC, or Oct key
> and print it out as a JWK:
>
>     https://github.com/mitreid-connect/json-web-key-generator
>
>
> Whenever we deploy a new copy of our server somewhere, we also pull down
> this program and run it to generate a new JWK key set (with public and
> private keys) that we use to start up the server. The alternative, which
> we used to do, was to use OpenSSL to generate a self-signed X509
> certificate that we effectively threw away the trust chain for -- lots
> of extra effort to create information that we didn't want and then
> ignore it on the far end, all to get a simple keypair. It was
> unnecessarily complex from all ends, and the switch to JWK has been much
> nicer to deal with.
>
Is the simplicity of making a demo application running fast a major 
factor of preferring JWK to self-signed X509  ? What about the 
synchronization between the existing X509-based key storage and the new 
JWK-aware storages ?

Thanks, Sergey

>   -- Justin
>
> On 08/14/2014 09:25 AM, Richard Barnes wrote:
>> Hey Sergey,
>>
>> JWK isn't necessarily tied to JWE or JWS.  It can be used to represent
>> the public key that was used to encrypt a JWE (so that the recipient
>> can look up the private key), or the public key that should be used to
>> verify a JWS.  But it can also be used in other contexts.  For
>> example, WebCrypto uses JWK (among others) as a format for serializing
>> keys.
>> https://dvcs.w3.org/hg/webcrypto-api/raw-file/tip/spec/Overview.html#subtlecrypto-interface-datatypes
>>
>> As that link suggests, JWK is effectively the same as the PKCS#8
>> format for private keys and the SubjectPublicKeyInfo format for public
>> keys -- just in JSON instead of ASN.1.  It's a way to ship a key from
>> one place to another, for whatever reason you need to do that.
>>
>> Hope that helps,
>> --Richard
>>
>>
>>
>>
>>
>> On Thu, Aug 14, 2014 at 5:51 AM, Sergey Beryozkin
>> <[e-mail] <mailto:[e-mail]>> wrote:
>>
>>     Hi,
>>
>>     This is very likely a newbie question. What is the role of JWK ?
>>     According to [1] it is "... a (JSON) data structure that
>>     represents a cryptographic key".
>>
>>     I can see plenty examples of JWK in the JWE specification. JWS and
>>     JWE headers can have a "jwk" property representing a given JWK.
>>
>>     What confuses me is that the examples in JWE use JWK to describe
>>     the private parts of a given key. For example, when we talk about
>>     the RSA OAEP key encryption, JWK would show a private exponent of
>>     a given RSA key (JWE A1). Same for Aes Wrap secret key (JWE A3). Etc.
>>
>>     So clearly one would not use a "jwk" JWE header to pass around a
>>     JWK representation of the key which was used to encrypt the
>>     content encryption key.
>>
>>     So I'm thinking a JWK is:
>>     - a convenient way to describe a cryptographic key for JWE/JWS
>>     specifications to refer to it in the spec examples.
>>     - perhaps there's a long-term vision that the key stores would
>>     support JWK format directly ?
>>     - JWK is a 'container' for various key properties, some of those
>>     'public' properties can be passed around as a JWE/JWS header;
>>
>>     Am I on the right track, can someone please clarify it further ?
>>
>>     Thanks, Sergey
>>
>>
>>     [1]
>>     http://tools.ietf.org/html/draft-ietf-jose-json-web-key-31#section-1
>>
>>     _______________________________________________
>>     jose mailing list
>>     [e-mail] <mailto:[e-mail]>
>>     https://www.ietf.org/mailman/listinfo/jose
>>
>>
>>
>>
>> _______________________________________________
>> jose mailing list
>> [e-mail]
>> https://www.ietf.org/mailman/listinfo/jose
>