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Bouncy Castle JCA provider incorrectly declares that its Cipher, Mac,
Signature, and KeyAgreement implementations accept arbitrary keys (
including AndroidKeyStore keys). As a result, when a Cipher, Mac,
Signature, or KeyAgreement instance is requested from JCA without
explicitly specifying the provider (which follows best practices)
and then initialied with an AndroidKeyStore key, JCA chooses the
BouncyCastle's implementation, which in turn blows up because it
can't handle such keys.

The workaround is to install Cipher, Mac, Signature, and
KeyAgreement implementations backed by AndroidKeyStore as a
higher-priority JCA provider than the Bouncy Castle one. This is
achieved by splitting out the above implementations from
AndroidKeyStoreProvider into AndroidKeyStoreBCWorkaroundProvider
and installing the AndroidKeyStoreProvider at the usual priority
(below Bouncy Castle) and the AndroidKeyStoreBCWorkaroundProvider
at above Bouncy Castle priority.
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