HW3-sol - 1. Modes of operation of AES AES is a block...

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1. Modes of operation of AES AES is a block cipher that combines 128 bit blocks of data along with a key to produce a cipher text. The key sizes are of 128, 192, or 256 bits. It is based on the Rijndael’s algorithm. Though AES has varying key sizes, the 802.11i’s implementation of the algorithm limits both the key and the block size to 128 bits. The following modes of operation are used by AES to convert a continuous data stream to blocks of data: (a) Electronic Code Block (ECB) – one block of input message is encrypted sequentially using the same key. (b) Counter Mode (CTR) – encrypts an arbitrary value, counter, and XORs it with data to produce the cipher text. (c) CCM, Counter Mode + CBC MAC – uses CBC in conjunction with the Counter mode to produce Message Integrity Code. (d) Offset Codebook Mode (OCB) – achieves both encryption and authentication in a single computation (e) Cipher Block Chaining (CBC) – each block of plain text is XORed with the previous cipher text block before being encrypted. The first block uses the
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HW3-sol - 1. Modes of operation of AES AES is a block...

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