Re: [jose] The role of JWK

[Justin Richer <[e-mail]>]

Sergey - it's an Apache licensed project. Copy away! (with attribution) :)

  -- Justin

On 08/14/2014 12:42 PM, Sergey Beryozkin wrote:
> 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
>>>
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>>
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