John, David, Franco,
Thank you for your interest in helping define a new KEM API for Java. We
agree that KEMs are an important mechanism and expect them to become
more prevalent in the future. We also agree that there are challenges
associated with retrofitting the current APIs (KeyGenerator, Cipher,
KeyAgreement, etc) to implement KEMs, and thus we plan to define a new
standard KEM API for Java.
Your experience will be valuable (as has your input so far) to help
shape the direction of the API and confirm that it is flexible enough to
meet your needs.
We will be following up with more details soon.
--Sean
On 8/18/22 9:37 PM, John Gray 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: https://datatracker.ietf.org/doc/draft-ounsworth-pq-composite-kem/
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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