Add OAEP encoding that uses SHA-256

[matehat]

This is mainly a clone of the OAEPEncoding class, but using a SHA-256 hash.

This has been verified as compatible with:

• WebCrypto RSA-OAEP encryption: https://developer.mozilla.org/en-US/docs/Web/API/SubtleCrypto/encrypt#rsa-oaep
• The following OAEP encryption example in Python cryptography package: https://cryptography.io/en/latest/hazmat/primitives/asymmetric/rsa/#encryption

Still to do: incorporate in the package RSA tests and name-based encoding resolution. I honestly don't know the best way to go about this. I'm really not familiar with the package standards in that regard.

---

Edit

Now, there's a single class OAEPEncoding that exposes new factories to use different digests. Only SHA256Digest has been tested and verified.

This PR does not break existing code in any way.

[mwcw]

Hi,

Thanks very much for this for testing take look at where sha256 is used as both mask and hash function.

[https://github.com/bcgit/bc-java/blob/master/core/src/test/java/org/bouncycastle/crypto/test/OAEPTest.java#L792]

and

[https://github.com/bcgit/bc-java/blob/master/core/src/test/java/org/bouncycastle/crypto/test/OAEPTest.java#L812]

MW

[epoberezkin]

@matehat - compatible with Haskell OAEP implementation in cryptonite as well (with default parameters in cryptonite, when I use withSHA256 constructor).

@mwcw - any reason not to merge it?

[epoberezkin]

It probably just misses doc comments...

[johannalamm]

It would be great if this could be merged😇🙏

[fredrik-w]

Would really like this merged! 🙏

[dharmadeveloper108]

It works great!! Would be awesome if it was merged! :)

[bryanlee-hdj]

By using this P.R, does it make usable the java Cipher class's "RSA/ECB/OAEPWithSHA-256AndMGF1Padding" on the Flutter? (I'm the newbie in the Crypto & Security fields =))

I'd like to know if this PR could handle the above algorithm case.

[bkhezry]

Is there any update on when this PR will be merged?

[mwcw]

Is there any update on when this PR will be merged?

I am adding more tests to it and endeavouring to exercise OAEP more generally.
I may push a new release this evening or more probably Thursday AU, Melbourne time.

MW

[mwcw]

Thanks,

I added further testing to this mainly for SHA256.

It will be synced shortly.

MW