6.docx - Let us consider the block cipher type of symmetric encryption The basic idea is that you have a block of plaintext(for example 128 bits and a

# 6.docx - Let us consider the block cipher type of symmetric...

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Let us consider the block cipher type of symmetric encryption. The basic idea is that you have a block of plaintext (for example, 128 bits) and a key (for example, 128 bits) as inputs to the encryption algorithm. The output will be a block of cipher-text (for example, 128 bits). If the encryption algorithm does not conduct compression, the output block size will be at least as large as the plaintext block (in other words, the cipher text is of the same size or longer than the plaintext.) Please explain why it is like this. In the Block cipher symmetric algorithm, each text block that is going to be encrypted needs to be the same size as the block which is 128 bit in this case. For the text messages smaller than that

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Unformatted text preview: size extra bits would be added to the text to get to the same size of the block and get ready for the encryption, therefore the size would become larger than the initial message. For the larger messages, the text would be divided to 128 bit blocks and it is obvious that the last block would be the same size or shorter than 128 bit, so extra bits are needed to be added to the last block to make it the exact same size of the standard 128bit. It can be concluded that the overall message would be larger that the initial one in this case as well....
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