Product Cipher

Product Cipher

1. Prof. Neeraj Bhargava Mrs. Shubha Chaturvedi Department of Computer Science, School of Engineering & System Sciences MDS University Ajmer, Rajasthan PRODUCT CIPHER TECHNIQUE

2. It is product cipher is a combination of substitution and Transposition cipher. Product cipher , data encryption scheme in which the ciphertext produced by encrypting a plaintext document is subjected to further encryption. By combining two or more simple transposition ciphers or substitution ciphers, a more secure encryption may result. PRODUCT CIPHER TECHNIQUE

3. One of the most famous field ciphers of all time was a fractionation system, the  ADFGVX cipher   employed by the German army during World War I. This system used a 6 × 6 matrix to substitution-encrypt the 26 letters and 10 digits into pairs of the symbols A, D, F, G, V, and X.

4. Step-1 Substitution by modified polybius A D F G V X matrix. A D F G V X A D F G V X Example : F ind out the A D F G V X cipher for the: Plain text -> ” computer “ Key -> “lemon” L E M O N A B C D F G H I J K P Q R S T U V W X Y Z 1 2 3 4 5 6 7 8 9

5. Plain text -> C O M P U T E R Intermediate cipher text -> DD AG AF FG GF GD AD FX In the above step draw 6*6 matrix , and fill the grid with the random combination of 26 letters of the alphabets and then 10 digits .( 0 TO 9 ). STEP-2 Transposition by single columinar method . Apply the single columinar transposition to the above intermediate cipher text by using the second Keyword -> BREAD

6. Use matrix according to the length of key. B R E A D Intermediate Cipher text D D A G A F F G G F G D A D F X

7. Now Re-arrange the columns in the ascending order. A B D E R Plain text -> COMPUTER Cipher text -> GGD DFG AFF AGA DFD G D A A D G F F G A D G F A D

8. ASSIGNMENT Find out the A D F G V X cipher for the : Plain text -> ” CRYPTOGRAPHY“ Key -> “ATTACK”