On 8/17/2017 11:35 AM, Michael StJohns wrote:
On 8/17/2017 1:28 PM, Xuelei Fan wrote:
This is the same for ANY current publicly known curve - different
providers may implement all some or none of them. So extending this
model for the curve25519 stuff isn't going to be any different old
provider and new provider wise than is currently the case. If you
want the new curves, you have to specify the new providers. If the
new and old providers don't implement the same curves, you may need
to deal with two different providers simultaneously - and that's not
something that just happens.
I see your points. Not-binding to a provider cause problems; binding
to a provider cause other problems. There are a few complains on the
problems, and impact the real world applications in practice.
Basically, this is a failing of imagination when the various
getInstance() methods were defined. Now its possible to use
Security.getProvider(Map<String,String>) to good effect (but more work)
to find appropriate providers for appropriate signature/key agreement
algorithms and curves.
I'm not sure how this applies to the compatibility impact concern. See
more in the example bellow.
I don't think your concerns are valid. I may still be missing
something here - but would ask for a real-world example that actually
shows breakage.
I happened to have a real-world example. See
https://bugs.openjdk.java.net/browse/JDK-8064330
I'm not sure how this applies to the current question of whether or not
its possible to integrate new EC curves?
This is an interesting bug. At first it is requested to support
SHA224 in JSSE implementation. And, SHA224 is added as the supported
hash algorithm for TLS. However, because SunMSCAPI does not support
SHA224 signature, compatibility issues comes. So we removed SHA224 if
the SunMSCAPI is presented. Later, one found the code is unusual as
SHA224 and the related signature algorithms are supported by the
underlying providers, look like no reason to limit the use of SHA224.
So, SHA224 is added back and then the compatibility issues come back
again. Then we removed SHA224 again if the SunMSCAPI is presented.
However, at the same time, another request is asking to support SHA224
on Windows. The API design itself put me in a either-or situation. I
would try to avoid it if possible for new design.
This appears to be an MSCAPI issue vice a JSSE issue.
MSCAPI is fine as it does not support SHA224. JSSE is then in a bad
position because it cannot support SHA224 in a general way even one of
the underlying provider supports SHA224 but another one not.
And the JCA
specifically disclaims the guaranteed ability to use cryptographic
objects from one provider in another provider.
It's not the real problem. The real problem is that there is a provider
support the requested algorithms, why not use it? We can say, the spec
does not guarantee the behavior, but the application still has a
problem. We also can say, we have a design flaw, but the question is
still there.
Secondary users like
the JSSE probably need to stick to a single provider for a given connection.
Stick to a single provider will open other windows for different
problems. JCE spec does not grant one provider could implement all
services.
Treat these simply as new curves and let's move forward with very
minimal changes to the public API.
I would like to treat it as two things. One is to support new curves
for new forms. The other one is to support named curves [1]. For the
support of new forms, there are still significant problems to solve.
For the support of named curves (including the current EC form), looks
like we are in a not-that-bad situation right now. Will the named
curves solution impacts the support of new curves APIs in the future?
I don't see the impact yet. I may missing something, but I see no
reason to option out the named curves support.
I'm not sure why you think this (the example in [1]) can't be done?
I gave the example elsewhere, but let me expand it with my comment above
(possibly faking the hash key names - sorry):
HashMap<String,String> neededAlgs = new HashMap<>();
neededAlgs.put("Signature.EdDSA", "");
neededAlgs.put("AlgorithmParameters.EC SupportedCurves", "ed25519")
Provider[] p = Security.getProviders(neededAlgs);
if (p == null) throw new Exception ("Oops");
AlgorithmParameters parameters = AlgorithmParameters.getInstance("EC", p[0]);
parameters.init(new ECGenParameterSpec("ed25519"));
ECParameterSpec ecParameters =
parameters.getParameterSpec(ECParameterSpec.class);
return KeyFactory.getInstance("EC", p[0]).generatePublic(new
ECPublicKeySpec(new ECPoint(x, y), ecParameters));
Hm, good example!
But it is really too weight to use for general application development.
In the example, two crypto operations ("EC" AlgorithmParameters and "EC"
KeyFactory) are supported in the same provider. In practice, two
crypto operations may be supported in different providers.
If you're talking more generally, NamedCurves should be a form of
ECParameterSpec so you can read the name from the key, but there's no
support for adding names to that spec. Maybe extend it? E.g.:
package java.security.spec;
public class NamedECParameterSpec extends ECParameterSpec {
private Collection<String> names;
private Collection<Oid> oids;
public NamedECParameterSpec (EllipticCurve curve, ECPoint g,
BigInteger n, int h, Collection<String> names, Collection<Oid> oids) {
super (curve, g, n, h);
if (names != null) {
this.names = new ArrayList<String>(names);
}
if (oids != null) {
this.oids = new ArrayList<Oid>(oids);
}
}
public Collection<String> getNames() {
if (names == null)
return (Collection<String>)Collections.EMPTY_LIST;
else
return Collections.unmodifiableList(names);
}
etc....
This makes it easier to get exactly what you want from a key.
Assuming the provider implements it.
I see your points. But my concerns are not really about it. Except the
confusing and possibility to map/convert Montgomery curve or Edwards
curve or other forms [3][4] to Weierstrass form, I did not see how the
new proposal solve the problems I described in the previous mails [1][2].
Xuelei
[1]:
http://mail.openjdk.java.net/pipermail/security-dev/2013-October/009105.html
[2]:
http://mail.openjdk.java.net/pipermail/security-dev/2017-August/016194.html
[3]: https://crypto.stanford.edu/pbc/notes/elliptic/explicit.html
[4]: http://mathworld.wolfram.com/EllipticCurve.html
