The type of buffering used during signing.
This property specifies the behaviour of the signer when operating with input stream.
The behaviour can be that incoming stream is rewound OR that temporary stream is created and all data are copied to it.
This property is useful, when you have the stream which doesn't support seek operation, for example internet stream or decompressor stream.
Then you can tell the writer not to attempt to rewind the stream.
Default value is sbmRewind