encrypt the remaining bytes in the buffer, add the padding
takes one byte and stores it in a buffer. If the buffer is already full it gets encrypted and written to output
input length not limited to multiples of block size. ensure that length of output buffer is sufficiently large (see below).
PaddedBufferedBlockCipher extends a block cipher or mode (CTR, CBC, ...) by the ability to process data that is not a multiple of the block size. The last block will be padded according to the chosen padding scheme. If the last block is full, then a additional padding block will be appended.