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For each sub-block, count the occurrence frequencies of letters from A to Z, which are saved in an array Cipher Freqs. Then, all d letters in the keyword are recovered. For example, if you find that the keyword length dis most likely to be 4, the ciphertext should be rearranged into sub-blocks as follows (note: As each sub-block contains hundreds of letters, the following diagram only shows part of each sub-block):ĬS3873 Lab Exercise of 4 NARXIRITUA YIL I! w Kiw M X LIII AM N х R HA PY TH F1:01: FX1 HAH!TAL! P! i Yii zii sil! 0 10 10 1 ili !! !!! THIQH WIG! subblock 1 Next, repeat the following procedure for each sub-block and determine one keyword letter for each sub-block. Next, your cracking program needs to find out the most likely keyword letter that encrypts each sub-block. According to Vigenere cipher, each sub-block is shifted by a certain number of positions in 0 to 25, which corresponds to a keyword letter among A to Z. The letters in each column constitute one sub-block. Consider one possible keyword period d and divide the ciphertext into d sub-blocks by arranging the ciphertext row by row and reading out letters column by column. Note that you may need to choose at least two possible values of d since there may not be an exact match. The corresponding value(s) of d are the most likely keyword period(s). Find the I.C.value(s) in Table 1 that are closest to the I.C. can be calculated by IYL-d d-IYL ICE 0.06 (2) For example, for English ciphertext with L = 26, typical I.C. On the other hand, for a language of an alphabet of Lletters, given a cipher of period d, the expected value of I.C. (N-1) (1) where N is the total number of letters in the ciphertext, no is the number of occurrences of letter A, ni is the number of occurrences of letter B, nz is the number of occurrences of letter C, and so on. can be obtained using the following equation:ĬS3873 Lab Exercise of 4 25 1.C.= on. Calculated from the provided ciphertext, an estimate of I.C. We can use index of coincidence (1.C.) to reduce keyword period possibilities.
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To decipher the Vigenere ciphertext, first determine the possible keyword period d.
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Write a computer program in Java to decipher the ciphertext. The attached file VigenereCipher.txt is a sample of ciphertext generated using a Vigenere cipher of unknown keyword period. Did you get the correct ciphertext? PUNGOD WE TRUST ALLOTHER SWE VIRUS KVOGENE REVO GENE REVIGENE REVIG CD VMS VXMCYX NPCSOPK VFA VZDZA E w S N F с E G A R R N E R QA The following is the main work of this lab. In the following table, the first row is the plaintext, the second row is the repeating keywords, and the third row is the ciphertext according to Vigenere cipher. All others, we virus scan." with the keyword "vigenere". Transcribed image text: LAB ACTIVITIES: To get a deep understanding of Vigenere cipher, try to encrypt a plaintext message "In God we trust. Show transcribed image text Expert Answer KXYQMTJLHTGUIZOWLANDHKKTQJYJSDJSDCUHCEPKGNVGSVSNFMPHGRKLTQKHQOAFGUDLIPYWQJLFLHCLAEZINVCCFTJANMSNFHOUKIDDYFGIVHRCUTKUANDYAGUYGUNVNVUOPKTCFTNQRWFAEJOUKFQDKULOFSYYZOEDAKETJSTCUHKDDFGNVCNQOAPQTJANISCJALFKBTSIPKTCJTUXUPUTKGNKFGCLBKJTJSNFZAUSMQFGULIVKMCFYKFFCFTEGNXGLWLIQFSVZOWKAPVSQXDQJMCFTCLOOKIPLOYZIEZGQVHCKPWLAOQSVACRGSUABKDIVQFQJNQLIEANISNCVUNLSCUTCFDHAGWJIPYOWLIVKPWJPQJTWHTQSBQMTKLSRJIOSRAKCJGONVAAKAEZINVTJANMKNCLUTSLNQOPDYQXPNSYDMTOSNASFQJMQXPNSYEGNVSIPKDKKCKHLKFATQAELOTKYQMCCFTFGTJASQJTJSTRMTUQOWGUVKHQOSCUHKDDVZAVATOMSVLHKFKRJAELIESLNQOTXAKDNQOIHLHTGUIZOWLCJALFZOQVADJAKFHCKNQGPRGSKLIQFIVASRDAKFTJSTKLWKDLCLTCANCHOUATKGNQXSVSTWKQWGAUOIVZOWJOTVIPSRASNKEANKMCFKPGWUFOVOHASCQODQYOTDIQFWCKNQLBQJNYATJSBTSIPGNCHATOIVZOWJSYZYUMCJSNKEANKCCFNQLAFVSWTTTSCVGRQTTCANHJOOTOQCSCFDUUHQGLKFGVZAVHATSMQMNVHOUATKGNYZIEZMCFHQDDULOFSY
#How to use index of coincidence to decipher text code
Provide the complete source code with the output on a screenshot.
![how to use index of coincidence to decipher text how to use index of coincidence to decipher text](http://practicalcryptography.com/media/cryptanalysis/files/ss_graph.png)
Write a Java program to decipher the ciphertext.