What's wrong with IBM's JCE provider?

Question

I have a JCE test that works fine with all Sun JDKs I have tried, but fails with various IBM J9 JDKs (e.g. 1.6.0 build pwi3260sr8-20100409_01(SR8)). The exception below happ

Answer 1

@T.Rob commented that you may have made a mistake in encrypting with the private key. If "everyone" knows the public key, then anyone can decrypt your file. IBM's JCE behaviour is thus protecting people against this mistake.

I can see the logic of that.

However, there may be cases where you really do need to encrypt with the private key; e.g. as part of a protocol that needs to prove that you know the private key corresponding to a published public key.

If this is really what you want to do, you probably need to use a recent Sun JCE implementation (older Sun JCEs didn't implement RSA), or Bouncy Castle.