Re: posting to public-webcrypto, and a user report

What WebCrypto implementation are you using for your tests?

(1) It should be easy to accomplish what you want using the "spki" or
"pkcs8" key formats.
If you export the RSA-OAEP key as "spki" then the algorithm identifier will
be set to the generic rsaEncryption, and there will be no key usages
enumerated in the output.
You are free to re-import this for any RSA algorithm, using any key usages.

(2) The same thing can be accomplished with JWK. Following export you will
need to delete the "alg" and "key_ops" members of the exported JWK (as they
restrict it to a particular algorithm and key usages respectively)

(3) I suspect the actual problem you are hitting with regards to usage is
that you are trying to import a private key with the 'encrypt' usage, and
vice versa import  public key using the 'decrypt' usage.

When using the "jwk" format, you CANNOT import a private key as a public
key (even though it contains all of the public key properties). A private
key is identified by having a "d" member on the JWK. f you want to import
for RSA-OAEP from JWK with the 'encrypt' usage then you will need to delete
the "d" member from your JWK private key.

Cheers

On Fri, Dec 5, 2014 at 9:39 AM, Jason Proctor <jason@mono.hm> wrote:

> On Fri, Dec 5, 2014 at 2:44 AM, Anders Rundgren <
> anders.rundgren.net@gmail.com> wrote:
>
>>  On 2014-12-05 03:02, Jason Proctor wrote:
>>
>>
>>  the main issue i ran into was related to (surprise) usages. if for
>> example i generate an RSA key pair, and happily encrypt and decrypt with
>> it, then export the public key, then i instantly lose its encryption
>> capability. this was a surprise, to say the least -- this is a *public* key
>> we're dealing with.
>>
>>
>> Hi Jason,
>> it seems that in practice (deployment-wise) there are only plain RSA
>> encryption keys.  I have managed importing like this:
>>
>>     var encryption_key = {kty:'RSA',  alg:'RSA-OAEP-256',
>> n:'yz1k8Hbi5aTE4t...ZrHNTQAfvw', e:'AQAB'}
>>     var asym_alg = {name: 'RSA-OAEP', hash: {name: 'SHA-256'}};
>>     crypto.subtle.importKey('jwk', encryption_key, asym_alg, true,
>> ['encrypt']).then (function(public_key) {
>>     crypto.subtle.encrypt(asym_alg, public_key, data).then
>> (function(encryped_data) {
>>
>> Cheers,
>> Anders
>>
>>
> hi Anders,
>
> thanks for your response.
>
> partial success. i exported a public key to JWK, then removed the key_ops
> and ext properties so as to mirror your structure. i can now import the
> public key for *encrypt* but not *decrypt*, which is the opposite of the
> situation i had before.
>
> so to make this work i would have to persist two differently exported
> public keys, which is not a disaster, i suppose :-) but this mechanism does
> seem little arbitrary.
>
> i could almost understand this if the API enforced public key import and
> export via certificates, but i don't see any cert support at all! :-S
>
> best regards
> Jason
>
>