This question concerns block cipher padding. Suppose the block cipher has a block size of 18 bytes. A certain message ends with a partial block which is 5 bytes. We must reversibly pad out the message...

Extracted text: This question concerns block cipher padding. Suppose the block cipher has a block size of 18 bytes. A certain message ends with a partial block which is 5 bytes. We must reversibly pad out the message to use some block cipher modes, such as CBC (even if the last block is full). Consider the following padding strategy. Append a single byte with value 128, and then as many zero bytes as required to make the overall length a multiple of 18. Suppose the final (possibly partial) block of the message is "Ox0001020304" in hexadecimal. Write out the complete final block in hexadecimal. Please do not put a leading Ox as this has been written already. Ox