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'''Comparison of Block Cipher Modes''' | '''Comparison of Block Cipher Modes''' | ||

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+ | You may study the modes together, but please work out these answers on your own. Summative Grading Assignment. | ||

Complete each question described below. When comparing blocks of ciphertext or plaintext, if corresponding blocks differ then mention which specific blocks differ. If they differ by only 1 bit, mention that fact specifically. If they differ by more than 1 bit, simply state the specific blocks that differ completely. If all blocks differ in the full ciphertext, simply state that there is no relationship. Be as precise as you can in your comparisons to illustrate that you understand the various modes. | Complete each question described below. When comparing blocks of ciphertext or plaintext, if corresponding blocks differ then mention which specific blocks differ. If they differ by only 1 bit, mention that fact specifically. If they differ by more than 1 bit, simply state the specific blocks that differ completely. If all blocks differ in the full ciphertext, simply state that there is no relationship. Be as precise as you can in your comparisons to illustrate that you understand the various modes. | ||

- | * Suppose two plaintext samples P and Q are encrypted using a block cipher with the same secret key K and the same initialization vector IV (or nonce) for those modes that require it. Suppose each plaintext sample is divided into 100 blocks (including padding). If all the plaintext blocks are the same except they differ only by 1 bit in block 10, compare the corresponding ciphertext for each block cipher mode | + | * Suppose two plaintext samples P and Q are encrypted using a block cipher with the same secret key K and the same initialization vector IV (or nonce) for those modes that require it. Suppose each plaintext sample is divided into 100 blocks (including padding). If all the plaintext blocks of P and Q are the same, except for block 10, in which they differ by 1 bit, compare the corresponding ciphertext for each block cipher mode |

** ECB | ** ECB | ||

** CBC | ** CBC |