{"id":50,"date":"2018-07-11T09:49:09","date_gmt":"2018-07-11T09:49:09","guid":{"rendered":"http:\/\/itp4.epgpbooks.inflibnet.ac.in\/?post_type=chapter&#038;p=50"},"modified":"2019-05-13T11:37:34","modified_gmt":"2019-05-13T11:37:34","slug":"polyalphabetic-ciphers","status":"publish","type":"chapter","link":"https:\/\/ebooks.inflibnet.ac.in\/itp4\/chapter\/polyalphabetic-ciphers\/","title":{"rendered":"polyalphabetic ciphers"},"content":{"raw":"<div><span style=\"float: right;\"><a href=\"https:\/\/youtu.be\/6fFSgLvIKXA\" target=\"_blank\" rel=\"noopener\"><img src=\"http:\/\/epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/2018\/11\/download.png\" alt=\"epgp books\" width=\"75px\" height=\"75px;\" \/><\/a>\r\n<\/span><\/div>\r\n\r\n<strong>Homophonic substitution ciphers:<\/strong>\r\n<ul>\r\n \t<li style=\"text-align: justify\">Homophonic substitution cipher maps a character to more than one code. For example, \u201cA\u201d could correspond to 3, 15, 23; while for \u201cB\u201d this could be 5, 17, 21.<\/li>\r\n \t<li style=\"text-align: justify\">This type of substitution makes cryptanalysis or brute force harder but it doesn\u2019t hide all statistical properties.<\/li>\r\n \t<li style=\"text-align: justify\">With the help of powerful computer this can be broken in a few seconds.<\/li>\r\n<\/ul>\r\n<strong>Polyalphabetic Cipher:<\/strong>\r\n<ul>\r\n \t<li>Monoalphabetic substitution rules are used.<\/li>\r\n \t<li>Key decides which monoalphabetic substitution is to be performed.<\/li>\r\n<\/ul>\r\n<strong>Vigenere Cipher:<\/strong>\r\n<ul>\r\n \t<li>P=p0p1p2\u2026\u2026pn-1<\/li>\r\n \t<li>K=k0k1k2\u2026\u2026km-1<\/li>\r\n \t<li>C=C0C1C2\u2026\u2026Cn-1<\/li>\r\n \t<li>C=E(K,P) = E[(k0k1k2\u2026\u2026km-1, p0p1p2\u2026\u2026pn-1)]<\/li>\r\n<\/ul>\r\n=(p0+k0) mod 26, (p1+k1) mod 26, \u2026(pm-1+km-1) mod 26, (pm+k0) mod 26 \u2026 K is of length m. For m letters of plaintext , key is used. For the next m letters of plaintext, the key letters are repeated until all plaintext letters are used.\r\n<ul>\r\n \t<li>Pi=(Ci \u2013 ki mod m) mod 26<\/li>\r\n<\/ul>\r\n<img class=\"size-full wp-image-51 aligncenter\" src=\"http:\/\/itp4.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-23.png\" alt=\"\" width=\"861\" height=\"516\" \/>\r\n\r\n<strong>Vigenere Cipher:<\/strong>\r\n<ul>\r\n \t<li>Key : mask<\/li>\r\n \t<li>Plaintext : meetmeatfield<\/li>\r\n \t<li>Ciphertext :<\/li>\r\n<\/ul>\r\n<img class=\"size-full wp-image-52 aligncenter\" src=\"http:\/\/itp4.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-24.png\" alt=\"\" width=\"870\" height=\"271\" \/>\r\n\r\n&nbsp;\r\n\r\n<strong>Strength of Vigenere Cipher:<\/strong>\r\n<ul>\r\n \t<li>The letter frequency is masked. But key is repeated so for the same plaintext letter and key letter \u2013 same ciphertext letter is achieved.<\/li>\r\n \t<li>For meet and me \u2013 me generates same ciphertext ye because key is repeated.<\/li>\r\n<\/ul>\r\n<strong>Autokey system:<\/strong>\r\n<ul>\r\n \t<li>Periodic nature of the keyword can be overcomed by nonrepeating keyword that is as long as an autokey system.<\/li>\r\n \t<li>Key word is concatenated with plaintext to provide a running key.<\/li>\r\n \t<li>Key : mask meet meatf<\/li>\r\n \t<li>Plaintext : meetmeatfield<\/li>\r\n \t<li>Ciphertext :<\/li>\r\n<\/ul>\r\n<img class=\"alignnone size-full wp-image-53\" src=\"http:\/\/itp4.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-25.png\" alt=\"\" width=\"849\" height=\"196\" \/>\r\n\r\n<strong>VERNAM cipher:<\/strong>\r\n<ul>\r\n \t<li>Cipher works on binary data(bits)<\/li>\r\n \t<li>ci=pi ki<\/li>\r\n<\/ul>\r\nWhere\r\n\r\nPi = ith binary digit of plaintext\r\n\r\nKi = ith binary digit of key\r\n\r\nci = ith binary digit of ciphertext\r\n<ul>\r\n \t<li>= exclusive \u2013 or (XOR) operation pi=ci \u00c5 ki<\/li>\r\n<\/ul>\r\n<strong>One \u2013 Time pad:<\/strong>\r\n<ul>\r\n \t<li>The key is used to encrypt and decrypt a single message, then key is discarded.<\/li>\r\n \t<li>Each new message requires a new key of the same length as the new message. Such a scheme, is known as a one-time pad.<\/li>\r\n \t<li>One time pad is unbreakable.<\/li>\r\n \t<li>No statistical relationship to the plaintext.<\/li>\r\n \t<li>Includes space so 27 characters scheme.<\/li>\r\n<\/ul>\r\n<strong>One \u2013 Time pad Example:<\/strong>\r\n<ul>\r\n \t<li>Plaintext : mr mustard<\/li>\r\n \t<li>key : pxlmvmsydo<\/li>\r\n \t<li>Ciphertext : ANKYODKYUR<\/li>\r\n \t<li>Plaintext : miss scarl<\/li>\r\n \t<li>Key : pftgpmiydg<\/li>\r\n \t<li>Ciphertext : ANKYODKYUR<\/li>\r\n<\/ul>\r\n<p style=\"text-align: justify\">Cryptanalyst can find keys and can not decide which plaintext is true and which key is correct.<\/p>\r\n&nbsp;\r\n\r\n<strong>One Time pad \u2013 Difficulties in using:<\/strong>\r\n<ul>\r\n \t<li>Practically difficult to generate large quantities of random keys.<\/li>\r\n \t<li style=\"text-align: justify\">How to distribute key and protect them. Because for every message , equal length of key is to be sent to sender and receiver.<\/li>\r\n<\/ul>\r\nOne time pad gives perfect secrecy. But limited use . Used only for highly secure low bandwidth channels.\r\n\r\n&nbsp;\r\n\r\n<strong>Transposition Techniques. \u2013 permutation of plaintext letters :<\/strong>\r\n\r\n&nbsp;\r\n\r\n<strong>Rail fence cipher:<\/strong>\r\n\r\n&nbsp;\r\n\r\nMessage \u201c all gather at lawn\u201d.\r\n\r\n&nbsp;\r\n\r\nRail fence depth 2\r\n\r\n&nbsp;\r\n\r\n<img class=\"alignnone size-full wp-image-54\" src=\"http:\/\/itp4.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-26.png\" alt=\"\" width=\"840\" height=\"349\" \/>\r\n\r\n<strong>Transposition Techniques. \u2013\u2013 Complex scheme:<\/strong>\r\n\r\n&nbsp;\r\n<ul>\r\n \t<li>permutation of plaintext letters<\/li>\r\n \t<li style=\"text-align: justify\">Write the message row by row , read column by column. Permutation is done by order of the column.<\/li>\r\n \t<li>Plaintext : discusstheformulainmeeting<\/li>\r\n<\/ul>\r\n<img class=\"alignnone size-full wp-image-55\" src=\"http:\/\/itp4.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-27.png\" alt=\"\" width=\"319\" height=\"538\" \/>\r\n<ul>\r\n \t<li>Ciphertext : ssfuntxisemiegduhraenctolmiy<\/li>\r\n \t<li>For key 3214, start with column labeled 1- column 3 in table. Write all the letters then column labeled 2 \u2013 column 2 in the table. Then column labeled 3 and 4.<\/li>\r\n \t<li>This type of transposition cipher is not secure because letter frequencies in ciphertext are same as plaintext.<\/li>\r\n \t<li>Cryptanalyst can put ciphertext in a matrix and play with column position.<\/li>\r\n<\/ul>\r\n<strong>Stegnography:<\/strong>\r\n<ul>\r\n \t<li>Plaintext message is hidden<\/li>\r\n \t<li>Simple method \u2013 An arrangement of words or letters in the message can give real message.<\/li>\r\n \t<li>Text : Driveon<span style=\"text-align: initial;font-size: 1em\"> Road Open passage.<\/span><\/li>\r\n \t<li>Hidden message : First letter of each word - DROP<\/li>\r\n<\/ul>\r\n<strong>Stegnography techniques:<\/strong>\r\n<ul>\r\n \t<li>Character Marking \u2013 Selected letters are overwritten in pencil and not visible unless hold at an angle to bright light<\/li>\r\n \t<li>Invisible ink \u2013 leave no visible trace until heat or some chemical is applied to the paper.<\/li>\r\n \t<li>Pin punctures \u2013 pin punctures on selected letters. Not visible unless the paper is held up in light.<\/li>\r\n<\/ul>\r\nAdvantage : hide the secret communication\r\n\r\nDisadvantage : Lot of overhead to hide few bits of information\r\n\r\n&nbsp;\r\n<table>\r\n<tbody>\r\n<tr>\r\n<td><strong>you can view video on polyalphabetic ciphers<\/strong><\/td>\r\n<td><a href=\"https:\/\/youtu.be\/6fFSgLvIKXA\" target=\"_blank\" rel=\"noopener\"><img class=\"alignnone wp-image-120\" src=\"http:\/\/epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/2018\/11\/download.png\" alt=\"\" width=\"36\" height=\"36\" \/><\/a><\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\n\r\n<strong>Suggested Reading:<\/strong>\r\n\r\n&nbsp;\r\n<ol>\r\n \t<li>Cryptography and Network Security Principles and Practice by William Stallings, sixth Edition, PEARSON.<\/li>\r\n \t<li>Security in Computing by Charles Pfleeger &amp; Shari Lawrence Pfleeger, fourth Edition, PEARSON.<\/li>\r\n \t<li>Network Security by Charlie Kaufman, Radia Perlman, Mike Speciner, second Edition, PHI.<\/li>\r\n \t<li>The Complete Reference \u2013 Network Security by Roberta Bragg, Mark Rhodes-Ousley &amp; Keith Strassberg, Tata McGraw Hill<\/li>\r\n \t<li>Network Security Bible by Eric Cole, Ronald Krutz, James Conley, Wiley<\/li>\r\n \t<li>Hacking 6 Exposed by Stuart McClure, Joel Scambray &amp; George Kurtz , Tata McGraw Hill .<\/li>\r\n \t<li><a href=\"http:\/\/www.snort.org\/\">www.snort.org<\/a><\/li>\r\n \t<li><a href=\"https:\/\/nmap.org\/\">https:\/\/nmap.org<\/a><\/li>\r\n<\/ol>\r\n&nbsp;","rendered":"<div><span style=\"float: right;\"><a href=\"https:\/\/youtu.be\/6fFSgLvIKXA\" target=\"_blank\" rel=\"noopener\"><img decoding=\"async\" src=\"http:\/\/epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/2018\/11\/download.png\" alt=\"epgp books\" width=\"75px\" height=\"75px;\" \/><\/a><br \/>\n<\/span><\/div>\n<p><strong>Homophonic substitution ciphers:<\/strong><\/p>\n<ul>\n<li style=\"text-align: justify\">Homophonic substitution cipher maps a character to more than one code. For example, \u201cA\u201d could correspond to 3, 15, 23; while for \u201cB\u201d this could be 5, 17, 21.<\/li>\n<li style=\"text-align: justify\">This type of substitution makes cryptanalysis or brute force harder but it doesn\u2019t hide all statistical properties.<\/li>\n<li style=\"text-align: justify\">With the help of powerful computer this can be broken in a few seconds.<\/li>\n<\/ul>\n<p><strong>Polyalphabetic Cipher:<\/strong><\/p>\n<ul>\n<li>Monoalphabetic substitution rules are used.<\/li>\n<li>Key decides which monoalphabetic substitution is to be performed.<\/li>\n<\/ul>\n<p><strong>Vigenere Cipher:<\/strong><\/p>\n<ul>\n<li>P=p0p1p2\u2026\u2026pn-1<\/li>\n<li>K=k0k1k2\u2026\u2026km-1<\/li>\n<li>C=C0C1C2\u2026\u2026Cn-1<\/li>\n<li>C=E(K,P) = E[(k0k1k2\u2026\u2026km-1, p0p1p2\u2026\u2026pn-1)]<\/li>\n<\/ul>\n<p>=(p0+k0) mod 26, (p1+k1) mod 26, \u2026(pm-1+km-1) mod 26, (pm+k0) mod 26 \u2026 K is of length m. For m letters of plaintext , key is used. For the next m letters of plaintext, the key letters are repeated until all plaintext letters are used.<\/p>\n<ul>\n<li>Pi=(Ci \u2013 ki mod m) mod 26<\/li>\n<\/ul>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"size-full wp-image-51 aligncenter\" src=\"http:\/\/itp4.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-23.png\" alt=\"\" width=\"861\" height=\"516\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-23.png 861w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-23-300x180.png 300w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-23-768x460.png 768w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-23-65x39.png 65w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-23-225x135.png 225w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-23-350x210.png 350w\" sizes=\"auto, (max-width: 861px) 100vw, 861px\" \/><\/p>\n<p><strong>Vigenere Cipher:<\/strong><\/p>\n<ul>\n<li>Key : mask<\/li>\n<li>Plaintext : meetmeatfield<\/li>\n<li>Ciphertext :<\/li>\n<\/ul>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"size-full wp-image-52 aligncenter\" src=\"http:\/\/itp4.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-24.png\" alt=\"\" width=\"870\" height=\"271\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-24.png 870w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-24-300x93.png 300w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-24-768x239.png 768w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-24-65x20.png 65w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-24-225x70.png 225w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-24-350x109.png 350w\" sizes=\"auto, (max-width: 870px) 100vw, 870px\" \/><\/p>\n<p>&nbsp;<\/p>\n<p><strong>Strength of Vigenere Cipher:<\/strong><\/p>\n<ul>\n<li>The letter frequency is masked. But key is repeated so for the same plaintext letter and key letter \u2013 same ciphertext letter is achieved.<\/li>\n<li>For meet and me \u2013 me generates same ciphertext ye because key is repeated.<\/li>\n<\/ul>\n<p><strong>Autokey system:<\/strong><\/p>\n<ul>\n<li>Periodic nature of the keyword can be overcomed by nonrepeating keyword that is as long as an autokey system.<\/li>\n<li>Key word is concatenated with plaintext to provide a running key.<\/li>\n<li>Key : mask meet meatf<\/li>\n<li>Plaintext : meetmeatfield<\/li>\n<li>Ciphertext :<\/li>\n<\/ul>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-53\" src=\"http:\/\/itp4.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-25.png\" alt=\"\" width=\"849\" height=\"196\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-25.png 849w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-25-300x69.png 300w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-25-768x177.png 768w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-25-65x15.png 65w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-25-225x52.png 225w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-25-350x81.png 350w\" sizes=\"auto, (max-width: 849px) 100vw, 849px\" \/><\/p>\n<p><strong>VERNAM cipher:<\/strong><\/p>\n<ul>\n<li>Cipher works on binary data(bits)<\/li>\n<li>ci=pi ki<\/li>\n<\/ul>\n<p>Where<\/p>\n<p>Pi = ith binary digit of plaintext<\/p>\n<p>Ki = ith binary digit of key<\/p>\n<p>ci = ith binary digit of ciphertext<\/p>\n<ul>\n<li>= exclusive \u2013 or (XOR) operation pi=ci \u00c5 ki<\/li>\n<\/ul>\n<p><strong>One \u2013 Time pad:<\/strong><\/p>\n<ul>\n<li>The key is used to encrypt and decrypt a single message, then key is discarded.<\/li>\n<li>Each new message requires a new key of the same length as the new message. Such a scheme, is known as a one-time pad.<\/li>\n<li>One time pad is unbreakable.<\/li>\n<li>No statistical relationship to the plaintext.<\/li>\n<li>Includes space so 27 characters scheme.<\/li>\n<\/ul>\n<p><strong>One \u2013 Time pad Example:<\/strong><\/p>\n<ul>\n<li>Plaintext : mr mustard<\/li>\n<li>key : pxlmvmsydo<\/li>\n<li>Ciphertext : ANKYODKYUR<\/li>\n<li>Plaintext : miss scarl<\/li>\n<li>Key : pftgpmiydg<\/li>\n<li>Ciphertext : ANKYODKYUR<\/li>\n<\/ul>\n<p style=\"text-align: justify\">Cryptanalyst can find keys and can not decide which plaintext is true and which key is correct.<\/p>\n<p>&nbsp;<\/p>\n<p><strong>One Time pad \u2013 Difficulties in using:<\/strong><\/p>\n<ul>\n<li>Practically difficult to generate large quantities of random keys.<\/li>\n<li style=\"text-align: justify\">How to distribute key and protect them. Because for every message , equal length of key is to be sent to sender and receiver.<\/li>\n<\/ul>\n<p>One time pad gives perfect secrecy. But limited use . Used only for highly secure low bandwidth channels.<\/p>\n<p>&nbsp;<\/p>\n<p><strong>Transposition Techniques. \u2013 permutation of plaintext letters :<\/strong><\/p>\n<p>&nbsp;<\/p>\n<p><strong>Rail fence cipher:<\/strong><\/p>\n<p>&nbsp;<\/p>\n<p>Message \u201c all gather at lawn\u201d.<\/p>\n<p>&nbsp;<\/p>\n<p>Rail fence depth 2<\/p>\n<p>&nbsp;<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-54\" src=\"http:\/\/itp4.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-26.png\" alt=\"\" width=\"840\" height=\"349\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-26.png 840w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-26-300x125.png 300w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-26-768x319.png 768w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-26-65x27.png 65w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-26-225x93.png 225w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-26-350x145.png 350w\" sizes=\"auto, (max-width: 840px) 100vw, 840px\" \/><\/p>\n<p><strong>Transposition Techniques. \u2013\u2013 Complex scheme:<\/strong><\/p>\n<p>&nbsp;<\/p>\n<ul>\n<li>permutation of plaintext letters<\/li>\n<li style=\"text-align: justify\">Write the message row by row , read column by column. Permutation is done by order of the column.<\/li>\n<li>Plaintext : discusstheformulainmeeting<\/li>\n<\/ul>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-55\" src=\"http:\/\/itp4.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-27.png\" alt=\"\" width=\"319\" height=\"538\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-27.png 319w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-27-178x300.png 178w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-27-65x110.png 65w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-27-225x379.png 225w\" sizes=\"auto, (max-width: 319px) 100vw, 319px\" \/><\/p>\n<ul>\n<li>Ciphertext : ssfuntxisemiegduhraenctolmiy<\/li>\n<li>For key 3214, start with column labeled 1- column 3 in table. Write all the letters then column labeled 2 \u2013 column 2 in the table. Then column labeled 3 and 4.<\/li>\n<li>This type of transposition cipher is not secure because letter frequencies in ciphertext are same as plaintext.<\/li>\n<li>Cryptanalyst can put ciphertext in a matrix and play with column position.<\/li>\n<\/ul>\n<p><strong>Stegnography:<\/strong><\/p>\n<ul>\n<li>Plaintext message is hidden<\/li>\n<li>Simple method \u2013 An arrangement of words or letters in the message can give real message.<\/li>\n<li>Text : Driveon<span style=\"text-align: initial;font-size: 1em\"> Road Open passage.<\/span><\/li>\n<li>Hidden message : First letter of each word &#8211; DROP<\/li>\n<\/ul>\n<p><strong>Stegnography techniques:<\/strong><\/p>\n<ul>\n<li>Character Marking \u2013 Selected letters are overwritten in pencil and not visible unless hold at an angle to bright light<\/li>\n<li>Invisible ink \u2013 leave no visible trace until heat or some chemical is applied to the paper.<\/li>\n<li>Pin punctures \u2013 pin punctures on selected letters. Not visible unless the paper is held up in light.<\/li>\n<\/ul>\n<p>Advantage : hide the secret communication<\/p>\n<p>Disadvantage : Lot of overhead to hide few bits of information<\/p>\n<p>&nbsp;<\/p>\n<table>\n<tbody>\n<tr>\n<td><strong>you can view video on polyalphabetic ciphers<\/strong><\/td>\n<td><a href=\"https:\/\/youtu.be\/6fFSgLvIKXA\" target=\"_blank\" rel=\"noopener\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-120\" src=\"http:\/\/epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/2018\/11\/download.png\" alt=\"\" width=\"36\" height=\"36\" \/><\/a><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p><strong>Suggested Reading:<\/strong><\/p>\n<p>&nbsp;<\/p>\n<ol>\n<li>Cryptography and Network Security Principles and Practice by William Stallings, sixth Edition, PEARSON.<\/li>\n<li>Security in Computing by Charles Pfleeger &amp; Shari Lawrence Pfleeger, fourth Edition, PEARSON.<\/li>\n<li>Network Security by Charlie Kaufman, Radia Perlman, Mike Speciner, second Edition, PHI.<\/li>\n<li>The Complete Reference \u2013 Network Security by Roberta Bragg, Mark Rhodes-Ousley &amp; Keith Strassberg, Tata McGraw Hill<\/li>\n<li>Network Security Bible by Eric Cole, Ronald Krutz, James Conley, Wiley<\/li>\n<li>Hacking 6 Exposed by Stuart McClure, Joel Scambray &amp; George Kurtz , Tata McGraw Hill .<\/li>\n<li><a href=\"http:\/\/www.snort.org\/\">www.snort.org<\/a><\/li>\n<li><a href=\"https:\/\/nmap.org\/\">https:\/\/nmap.org<\/a><\/li>\n<\/ol>\n<p>&nbsp;<\/p>\n","protected":false},"author":4,"menu_order":4,"template":"","meta":{"_acf_changed":false,"pb_show_title":"on","pb_short_title":"","pb_subtitle":"","pb_authors":["miss-hiteishi-diwanji"],"pb_section_license":""},"chapter-type":[],"contributor":[58],"license":[],"class_list":["post-50","chapter","type-chapter","status-publish","hentry","contributor-miss-hiteishi-diwanji"],"part":3,"_links":{"self":[{"href":"https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-json\/pressbooks\/v2\/chapters\/50","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-json\/pressbooks\/v2\/chapters"}],"about":[{"href":"https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-json\/wp\/v2\/types\/chapter"}],"author":[{"embeddable":true,"href":"https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-json\/wp\/v2\/users\/4"}],"version-history":[{"count":4,"href":"https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-json\/pressbooks\/v2\/chapters\/50\/revisions"}],"predecessor-version":[{"id":427,"href":"https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-json\/pressbooks\/v2\/chapters\/50\/revisions\/427"}],"part":[{"href":"https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-json\/pressbooks\/v2\/parts\/3"}],"metadata":[{"href":"https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-json\/pressbooks\/v2\/chapters\/50\/metadata\/"}],"wp:attachment":[{"href":"https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-json\/wp\/v2\/media?parent=50"}],"wp:term":[{"taxonomy":"chapter-type","embeddable":true,"href":"https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-json\/pressbooks\/v2\/chapter-type?post=50"},{"taxonomy":"contributor","embeddable":true,"href":"https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-json\/wp\/v2\/contributor?post=50"},{"taxonomy":"license","embeddable":true,"href":"https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-json\/wp\/v2\/license?post=50"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}