SOLUTION SET 1 B.TECH(CS) 4 TH YEAR CRYPTOGRAPHY & NETWORK SECURITY (ECS-084) 1. Attempt any four parts of the following:- [4x5=20] a). Give any three names of substitution techniques. party t u v w x y z
M O N A R C H Y B D E F G I/J K L P Q S T U V W X Z The matrix is constructed by filling in the letters of the keyword (minus duplicates) from left to right and from top to bottom, and then filling in the remainder of the matrix with the remaining letters in alphabetic order. The letters I and J count as one letter. Plaintext is encrypted two letters at a time, according to the following rules: 1. Repeating plaintext letters that would fall in the same pair are separated with a filler letter, such as x, so that balloon will be treated as ba lx lo on 2. Plaintext letters that would fall in the same row of matrix are each replaced with the letter to the right, with the first element of the row circularly following the last. For example, ar is encrypted as RM . 3. Plaintext letters that fall in the same column are each replaced by the letter beneath, with the top element of the row circularly following the last. For example, mu is encrypted as CM . 4. Otherwise, each plaintext letter is replaced by the letter that lies in its own row and the column occupied by the other plaintext letter. Thus, hs becomes BP , and ea becomes IM (or JM , as the encipherer wishes). As far as number of digrams is 26x26=676 is significantly greater than number of letters, frequency analysis becomes much more difficult. For these reasons, Playfair cipher was for a
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- Cryptography, Encryption, Advanced Encryption Standard, Block cipher