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<div class="moz-cite-prefix">I'd have to agree about PKCS 11.</div>
<div class="moz-cite-prefix"><br>
</div>
<div class="moz-cite-prefix">One more thing about the PQC KEMs - the
KDF step is built in. As you've mentioned, previously there's been
a lot of possible combinations with key agreement, with PQC KEMs
this has changed (of course, you could still use a KDF too, but
the original reasons for doing so no longer apply).</div>
<div class="moz-cite-prefix"><br>
</div>
<div class="moz-cite-prefix">Regards,</div>
<div class="moz-cite-prefix"><br>
</div>
<div class="moz-cite-prefix">David</div>
<div class="moz-cite-prefix"><br>
</div>
<div class="moz-cite-prefix">On 21/8/22 13:52, Michael StJohns
wrote:<br>
</div>
<blockquote type="cite"
cite="mid:6a9103b9-75ab-6bdf-465f-8d966d7d3476@comcast.net">
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<div class="moz-cite-prefix">On 8/20/2022 2:08 PM, David Hook
wrote:<br>
</div>
<blockquote type="cite"
cite="mid:6f95c68c-4cc6-a039-189e-1d4b75b16ca1@cryptoworkshop.com">
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<div class="moz-cite-prefix">Hi Michael,</div>
<div class="moz-cite-prefix"><br>
</div>
<div class="moz-cite-prefix">I don't know anything about
bureaucrats, I am an engineer. You may need to consult someone
else on bureaucrats. <br>
</div>
<p>I apologize for my apparent deficiencies in this area, but
would you mind explaining how Cipher.wrap() is either supposed
to take a public key and create an encapsulation based on it
and return a secret key implicitly in one clean move, or why
it even makes sense to do so. The method was never conceived
as providing the functionality for what a KEM actually does,
and when I did the initial PKCS11 implementation at Eracom in
the late 90's and the team at Sun added the wrap/unwrap
functions to support it, this is definitely not was intended
either - it was for explicit key wrapping based on the key
that was passed to Cipher.init().</p>
</blockquote>
<p>First - PKCS11 is a 40 year old API that probably needs to be
retired. I spent the better part of 2 years working with the
PKCS11 Oasis group trying to get them to properly support master
secrets and KDFs and failed utterly. You should not use PKCS11
as an example that the JCE should use as a goal. <br>
</p>
<p><br>
</p>
<p>At the base, a java class is a collection of objects. A Cipher
object <br>
</p>
<p>Let's build a non-parameterized ECIES-KEM which implicitly uses
AES256 bit keys to key a GCM cipher, and a KDF based on
SP800-108 counter mode with SHA256 as the underlying hash, and
with a well known label and context for the KDF since there is a
new key for every wrap.</p>
<p>1) Implement CipherSpi - <br>
</p>
<p>public class EciesKemCipher extends CipherSpi {</p>
<p> private KeyAgreement ka;<br>
private Cipher gcm;<br>
private KeyPair kp;<br>
private KeyPairGenerator kg;</p>
<p> EciesKemCipher() {<br>
ka = KeyAgreement.getInstance("ECDH");<br>
kpg = KeyPairGenerator.getInstance ("EC");<br>
gcm = Cipher.getInstance ("AES/GCM/NoPadding");<br>
</p>
<p> }</p>
<p> // implement a single example<br>
</p>
<p> @override <br>
protected void engineInit (int opMode, Key key, SecureRandom
dontcare) {</p>
<p> switch (opMode) {<br>
Cipher.MODE_WRAP:<br>
initWrap((ECPublicKey) key); <br>
break;<br>
default:<br>
// unimpl<br>
}<br>
}</p>
<p> private void initWrap (ECPublicKey k) {</p>
<p> ECParameterSpec spec = k.getParams();<br>
kpg.initialize(spec);<br>
kp = kpg.genKeyPair();<br>
ka.init (kp.getPrivate());<br>
ka.doPhase (k, true);<br>
byte[] sharedSecret = ka.generateSecret();</p>
<p> byte[] keyStream = kdf(sharedSecret, 32 + 12); //
output 44 bytes for Key and IV<br>
SecretKeySpec gcmKey = new SecretKeySpec (keyStream,
0, 32, "AES");<br>
IvParameterSpec gcmIv = new IVParameterSpec(keyStream,
32, 12);<br>
</p>
<p> gcm.init (Cipher.MODE_ENCRYPT, gcmKey, gcmIv);<br>
// all ready to go<br>
} <br>
<br>
</p>
<p> protected byte[] engineWrap (Key k) {</p>
<p> ByteBuffer outData = ByteBuffer.allocate
(k.getEncoded().length + kp.getPublic().getEncoded().length) +
16;</p>
<p> // Place a copy of the ephemeral public key I
generated in init here for the use of the receiver.<br>
outData.put (kp.getEncoded());<br>
// One s<br>
outData.put (gcm.doFinal(k.getEncoded());</p>
<p> outData.flip();<br>
byte[] result = outdata.remaining();</p>
<p> outData.get(result);<br>
// kp = null; clear cipher if it hasn't already been
cleared, clear ka if necessary (e.g. un-init)<br>
</p>
<p> return result;<br>
}<br>
</p>
<p> ... and unwrap and kdf function<br>
}</p>
<p><br>
</p>
<p>2) Implement a provider and add the above. <br>
</p>
<p><br>
</p>
<blockquote type="cite"
cite="mid:6f95c68c-4cc6-a039-189e-1d4b75b16ca1@cryptoworkshop.com">
<p>On BC's part, we've already implemented RFC 5990/SP 800-56B
in Java and the experience has, at best, been awkward. The new
algorithms have moved awkward to inappropriate. With the new
algorithms, there's no longer only one case of this, it's not
an outlier, there should be a general way of supporting KEMs
in the API that doesn't involve over engineering KeyGenerator
and Cipher.<br>
</p>
</blockquote>
<p>There's a big difference between the API and your underlying
implementation. Everything you want to do can be done using the
current APIs. As I said before, Cipher.wrap/unwrap are the
appropriate APIs for this as they meet the contract requirements
you need. Most Ciphers require some extra data -e.g. IVs -
that have to either be carried or implicitly derived. In this
case, what needs to be carried in addition to the encrypted key
material is at least the ephemeral public key the wrapper
creates. I used a very simple encoding scheme above and this
assumes that both ends know exactly what "ECIES-KEM" means.
Obviously, there are 100s of possible combinations of parameters
and KDFs and key wrap algorithms. What I would suggest is
heading over to LAMPS at the IETF and proposing a data encoding
scheme for carrying the parameters. Once you have that done,
then come here and map JCE names against parameter sets to close
the loop. It won't require an API change.<br>
</p>
<blockquote type="cite"
cite="mid:6f95c68c-4cc6-a039-189e-1d4b75b16ca1@cryptoworkshop.com">
<p> </p>
<p>I work with a team that has had to implement all of them and
had to make them fit into the JCA. We have done so. Like John,
I am simply relaying our experience. In about 18 months these
algorithms are going to become mandatory, what all of us think
is irrelevant. We, for our part, already have a solution, but
we both realize it's not "the solution" - we recognize that
the JVM is uniquely positioned to provide leadership on this
and provide a universal way of doing it.<br>
</p>
</blockquote>
<p>Then suggest an API and we'll start knocking it around. I
personally don't think its necessary at this time and will add
to API bloat.<br>
</p>
<blockquote type="cite"
cite="mid:6f95c68c-4cc6-a039-189e-1d4b75b16ca1@cryptoworkshop.com">
<p> </p>
<p>Of course, if it's felt that these algorithms should be
ignored, it's not my place to revolt, although I do feel
obliged to argue. I will simply try and do the best by my
users, as I have no doubt will John. Both of us have simply
offered our comments in good faith and to alert the community
that things have changed and that with these new algorithms
there is room for a new approach. The ambiguity about how
these algorithms can be implemented and the excessive need to
fallback on propritary classes for them does suggest that
there are some additions to the JCA which would help. I
appreciate to understand this statement does involve actually
understanding what these algorithms do and may require some
additional reading. <br>
</p>
<p>As I said, I'm an engineer, my users will be able to use
these algorithms properly, my team will ensure that, as I have
no doubt will John's. What John and myself, apparently
mistakenly, care about is that our users should also be able
to use these algorithms portably.</p>
<p>Are you saying portability is no longer a consideration?<br>
</p>
</blockquote>
<p>I have no idea where you got that idea.<br>
</p>
<blockquote type="cite"
cite="mid:6f95c68c-4cc6-a039-189e-1d4b75b16ca1@cryptoworkshop.com">
<p> </p>
<p>Regards,</p>
<p>David<br>
</p>
<div class="moz-cite-prefix"><br>
</div>
<div class="moz-cite-prefix"><br>
</div>
<div class="moz-cite-prefix">On 21/8/22 02:23, Michael StJohns
wrote:<br>
</div>
<blockquote type="cite"
cite="mid:783df5b7-e30f-08e7-dbc3-e3d95f427c18@comcast.net">
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<div class="moz-cite-prefix">Hi David/John -</div>
<div class="moz-cite-prefix"><br>
</div>
<div class="moz-cite-prefix">I would submit that you're trying
too hard to make your life simple! :-)</div>
<div class="moz-cite-prefix"><br>
</div>
<div class="moz-cite-prefix">Cipher.wrap/unwrap are the
correct methods.</div>
<div class="moz-cite-prefix"><br>
</div>
<div class="moz-cite-prefix">For example: <br>
</div>
<div class="moz-cite-prefix"><br>
</div>
<div class="moz-cite-prefix">Cipher kem = Cipher.getInstance
("ECIES/GCM-128-64/KDF-SP800-108-COUNTER-SHA256");</div>
<div class="moz-cite-prefix">kem.init (Cipher.WRAP_MODE,
pubkey);</div>
<div class="moz-cite-prefix">byte[] opaqueEncapsulatedKey =
kem.wrap (someOtherKey);</div>
<div class="moz-cite-prefix"><br>
</div>
<div class="moz-cite-prefix">The "opaqueEncapsulatedKey" would
contain the data needed by the unwrap function -
specifically a) the ecies ephemeral public key, b) the fact
that the derived key is a GCM key of length 128 and that the
GCM tag is 64 bytes long, c) the KDF, d) (optional) any
mixins other than defaults required by the KDF - which would
be passed in a parameter blob during init. Cipher would NOT
return the underlying generated secret used to wrap the
key. Just the public part of the key pair used to do the
ECDH operation against the passed in public key. In the
RSA case, the wrapped encrypting secret would be an opaque
data blob and would be part of the data passed to the unwrap
function.<br>
</div>
<div class="moz-cite-prefix"><br>
</div>
<div class="moz-cite-prefix">If you want a key generated for
other purposes, then the right thing is using a KDF and a
Key agreement function in tandem. Strangely the KDF
appears in the javacard API for 3.1, but not in the JCE/JDK
API.</div>
<div class="moz-cite-prefix"><br>
</div>
<div class="moz-cite-prefix">"What's the difference between a
bureaucrat and an engineer? A bureaucrat takes small
solvable pieces and combines them into one insoluble mass."</div>
<div class="moz-cite-prefix"><br>
</div>
<div class="moz-cite-prefix">In this case, Java provides a
number of flexible primitives that can be combined as
needed. In this case, the underlying Cipher implementation
would wrap key agreement and kdf and cipher (GCM)
instances. It should return UnsupportedOperationException
for all operations execept wrap/unwrap and the appropriate
init methods.</div>
<div class="moz-cite-prefix"><br>
</div>
<div class="moz-cite-prefix">Later, Mike<br>
</div>
<div class="moz-cite-prefix"><br>
</div>
<div class="moz-cite-prefix"><br>
</div>
<div class="moz-cite-prefix"><br>
</div>
<div class="moz-cite-prefix">On 8/19/2022 6:38 PM, David Hook
wrote:<br>
</div>
<blockquote type="cite"
cite="mid:d511fabf-74dd-ec49-b686-a90eca14861a@cryptoworkshop.com">
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<div class="moz-cite-prefix">Hi Mike,</div>
<div class="moz-cite-prefix"><br>
</div>
<div class="moz-cite-prefix">KEMs can be used for key
wrapping - we've actually implemented support for this
too. But they are not actually key wrapping ciphers.<br>
</div>
<div class="moz-cite-prefix"><br>
</div>
<div class="moz-cite-prefix">Here's a simple example of
using Kyber for key wrapping in BC:</div>
<div class="moz-cite-prefix"><br>
</div>
<div class="moz-cite-prefix">
<pre style="background-color:#ffffff;color:#080808;font-family:'JetBrains Mono',monospace;font-size:11.3pt;"><span style="color:#000000;">SecretKey key </span>= <span style="color:#0033b3;">new </span>SecretKeySpec(<span style="color:#000000;">keyBytes</span>, <span style="color:#067d17;">"AES"</span>);
<span style="color:#000000;">w1</span>.init(<span style="color:#000000;">Cipher</span>.<span style="color:#871094;font-style:italic;">WRAP_MODE</span>, kp.getPublic(), <span style="color:#0033b3;">new </span>KEMParameterSpec(<span style="color:#067d17;">"AES-KWP"</span>));
<span style="color:#0033b3;">byte</span>[] <span style="color:#000000;">data </span>= <span style="color:#000000;">w1</span>.wrap(<span style="color:#000000;">key</span>);
<span style="color:#000000;">Cipher w2 </span>= <span style="color:#000000;">Cipher</span>.<span style="font-style:italic;">getInstance</span>(algorithm, <span style="color:#067d17;">"BCPQC"</span>);
<span style="color:#000000;">w2</span>.init(<span style="color:#000000;">Cipher</span>.<span style="color:#871094;font-style:italic;">UNWRAP_MODE</span>, kp.getPrivate(), <span style="color:#0033b3;">new </span>KEMParameterSpec(<span style="color:#067d17;">"AES-KWP"</span>));
<span style="color:#000000;">Key k </span>= <span style="color:#000000;">w2</span>.unwrap(<span style="color:#000000;">data</span>, <span style="color:#067d17;">"AES"</span>, <span style="color:#000000;">Cipher</span>.<span style="color:#871094;font-style:italic;">SECRET_KEY</span>);
The behavior in this case is in line with what is given in RFC 5990 for the RSA KEM. How it works is by using the key generated
by the KEM to create an AES-KWP key, which is then used to wrap keyBytes. The shortcoming is it means you have to generate the
secret key separately.
This is the problem though - a KEM can actually be used to generate a secret key for other purposes. For example, where
someone is trying to implement a hybrid KAS scheme. But there is currently no mechanism in the Java APIs for being able to
take advantage of this directly, hence our use of the KeyGenerator class and other people's attempts to make use of the KeyAgreement
class. The Cipher.wrap() returns a byte[] - to be used with a KEM for secret generation it would also have to return the
generated secret (I would probably also argue that passing a public key to wrap in order to generate an encapsulation of a
generated encrypted secret was not the correct use of the API either, but the fact remains a byte[] is not really going to cut it).
If you have any further questions, please feel free to ask. For what it is worth, I have been developing providers for the JCE/JCA since
the late 90's and am actually one of the people responsible for the introduction of the existing wrap/unwrap API in the Cipher class.
Thanks,
David
</pre>
</div>
<div class="moz-cite-prefix">On 20/8/22 07:53, Mike StJohns
wrote:<br>
</div>
<blockquote type="cite"
cite="mid:814F78E4-9932-427B-8B65-1AFE5F9D32E2@comcast.net">
<pre class="moz-quote-pre" wrap="">Hi This implemented as part of Javax.crypto.Cipher. See the Java doc for the wrap and unwrap methods.
Mike
Sent from my iPad
</pre>
<blockquote type="cite">
<pre class="moz-quote-pre" wrap="">On Aug 19, 2022, at 12:56, John Gray <a class="moz-txt-link-rfc2396E" href="mailto:John.Gray@entrust.com" moz-do-not-send="true"><John.Gray@entrust.com></a> wrote:
We are starting to make use of the new PQ algorithms adopted by NIST for prototyping and development of standards. In particular we are working on a composite KEM standard:
See: <a class="moz-txt-link-freetext" href="https://datatracker.ietf.org/doc/draft-ounsworth-pq-composite-kem/" moz-do-not-send="true">https://datatracker.ietf.org/doc/draft-ounsworth-pq-composite-kem/</a>
However, there is no KEM interface in the JCA (which make sense because these are new algorithms, although RSA-KEM has been out since 2010).
I can add one into our toolkit (and I think David may have already added on into BC), but I assume at some point there will be an official one added in Java and likely it won't be identical to what we do even if it is very close, which would cause backwards compatibility pain... Perhaps we could collaborate on extending the JCA to support KEM? Essentially it requires methods.
ss, ct := encapsulate(PublicKey)
ss := decapsulate(PrivateKey, ct)
-ss is a shared secret (could come back as a Java SecretKey if you wanted as it would usually be used to derive something like an AES afterwards)
-ct is a Cipher Text (a byte array would make sense)
-Public and Private Keys would use the regular public and private key interface.
-An object holding the ss and ct from the encapsulate() method could be returned, with accessor methods to get the ss and ct. It could be called 'EncapsulatedKEMData' for example.
Likely you would want a new type of KEM crypto object (like you have for Signature, MessageDigest, Cipher, Mac, SecureRandom, KeyAgreement.. etc). Calling it KEM would seem to make sense. 😊 It could also use similar calling patterns and have a KEM.initKEM(keypair.getPublic()) or KEM.initKEM(keypair.getPrivate()), and then you would just call KEM.encapsulate() or KEM.decapsulate(ct).
Then algorithms could be registered in providers as usual:
put("KEM.Kyber","com.blah.Kyber")
put("KEM.compositeKEM","com.entrust.toolkit.crypto.kem.compositeKEM")
Then the above methods (encapsulate and decapsulate) could be defined in that new object type. Then we would be able to make use of it and not have to worry about incompatibility issues down the road...
Cheers,
John Gray
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