Name: iiR10263 Date: 10/17/2003



Functions
protected int engineDoFinal(ByteBuffer input, ByteBuffer output)
and
protected int engineUpdate(ByteBuffer input, ByteBuffer output)
are implemented in javax.crypto.CipherSpi abstract class. The
specification states that these functions "continue a multiple-part
encryption or decryption operation (depending on how this cipher
was initialized), processing another data part." These functions are
not abstract and may remain unchanged in a CipherSpi
implementation class. So there will be no real decryption or
encryption process if they are called. Also it is not specified whether
method exceptions are thrown or not.

Also behaviour with "null" parameters is undefined. Current
implementation throws "NullPointerException" if one or both parameters
are "null".

Now, as far as I understand, the specification describes the following
confusing behaviour of these not overriden functions:
It is not specified whether method exceptions are thrown or not,
because cipher process is unspecified.
If there was no exception, positions in both buffers are advanced:
input position is advanced to input limit, output position is advanced
by return value(return value is unspecified).

The problem may be addressed by
 * making these functions abstract
 * making these functions throw "UnsupportedOperationException"
 * more detailed specification (how exactly buffers are changed and
   what and when method exceptions are thrown)


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