{"id":57,"date":"2018-07-11T10:01:04","date_gmt":"2018-07-11T10:01:04","guid":{"rendered":"http:\/\/itp4.epgpbooks.inflibnet.ac.in\/?post_type=chapter&#038;p=57"},"modified":"2019-05-13T11:49:16","modified_gmt":"2019-05-13T11:49:16","slug":"stream-ciphers-and-block-ciphers-feistel-cipher","status":"publish","type":"chapter","link":"https:\/\/ebooks.inflibnet.ac.in\/itp4\/chapter\/stream-ciphers-and-block-ciphers-feistel-cipher\/","title":{"rendered":"Stream ciphers and block ciphers, Feistel cipher"},"content":{"raw":"<div><span style=\"float: right;\"><a href=\"https:\/\/youtu.be\/M8EYofEoMM8\" 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>Stream Ciphers:<\/strong>\r\n<ul>\r\n \t<li>Stream cipher takes one bit or one byte at a time from digital data and encrypts.<\/li>\r\n \t<li>Vernam cipher is an example of stream cipher.<\/li>\r\n \t<li>pi = ith digit from binary form of plaintext, Ki = ith digit from binary form of key, ci = ith digit from binary form of ciphertext<\/li>\r\n \t<li>\u00c5 = exclusive \u2013 or (XOR) operation<\/li>\r\n \t<li>pi=ci \u00c5 ki<\/li>\r\n<\/ul>\r\n<strong>Block Cipher:<\/strong>\r\n<ul>\r\n \t<li>Block of plaintext is taken at a time and ciphertext block is produced.<\/li>\r\n \t<li>The block is of 64 bits or 128 bits.<\/li>\r\n \t<li>The block cipher processes n bits from the plaintext block to produce n bits of a ciphertext block.<\/li>\r\n<\/ul>\r\n<img class=\"size-full wp-image-58 aligncenter\" src=\"http:\/\/itp4.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-28.png\" alt=\"\" width=\"917\" height=\"591\" \/>\r\n\r\n<img class=\"size-full wp-image-59 aligncenter\" src=\"http:\/\/itp4.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-29.png\" alt=\"\" width=\"923\" height=\"790\" \/>\r\n\r\n<img class=\"size-full wp-image-60 aligncenter\" src=\"http:\/\/itp4.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-30.png\" alt=\"\" width=\"795\" height=\"730\" \/>\r\n\r\n<strong>Problem with Feistel - Ideal block cipher:<\/strong>\r\n\r\n&nbsp;\r\n<ul>\r\n \t<li>Ideal block cipher is like substitution cipher.<\/li>\r\n \t<li>As the block size is small, Vulnerable to statistical analysis.<\/li>\r\n \t<li>For large block size , ideal block building implementation and ideal block storing is infeasible.<\/li>\r\n \t<li>For 4 bits, 16 rows are needed. Required length of key is 64 bits (4 bits of16 rows). For n bits, nx2n bits.<\/li>\r\n \t<li>To prevent statistical attacks, block length must be 64 bits. So requires 64x264 bits.<\/li>\r\n \t<li>\r\n<ul>\r\n \t<li>Block cipher having k bits in key and n bits in a block. So 2k possible transformations not 2n!.<strong>Feistel Cipher:<\/strong><\/li>\r\n<\/ul>\r\n<ul>\r\n \t<li>Feistel suggested to use substitution and permutation alternatively to produce ciphertext.<\/li>\r\n<\/ul>\r\n<\/li>\r\n \t<li>Substitution- Each plaintext element is replaced by a corresponding element. Replacement is unique.<\/li>\r\n \t<li>Permutation -The order of plaintext element is changed.<\/li>\r\n<\/ul>\r\n<strong>Feistel cipher suggests confusion and diffusion. \u2013 to suppress statistical cryptanalysis:<\/strong>\r\n\r\n&nbsp;\r\n<ul>\r\n \t<li><strong>Diffusion<\/strong><\/li>\r\n<\/ul>\r\nOne plaintext digit affects in deriving the value of several ciphertext digit. Message M=m1m2m3\u2026. k consecutive letters are added to derive the letter of ciphertext yn\r\n\r\n&nbsp;\r\n\r\n<em>k<\/em>\r\n\r\n<em>y<\/em><em>n<\/em><em>\u00a0 <\/em>= (\u00e5<em>m<\/em><em>n<\/em>+<em>i<\/em> ) mod 26\r\n\r\n<em>i<\/em>=1\r\n\r\n&nbsp;\r\n\r\nStatistical relation between plaintext and ciphertext is intricate and it is tricky to derive key.\r\n\r\n&nbsp;\r\n<div>\r\n\r\n\u00b7\u00a0\u00a0<strong>Confusion<\/strong>\r\n\r\n&nbsp;\r\n\r\nThe statistical relationship between ciphertext and encryption key is so complex that it is difficult to derive key.\r\n\r\n&nbsp;\r\n\r\nConfusion is created by applying substitution algorithm in complex way.\r\n\r\n<img class=\"size-full wp-image-61 aligncenter\" src=\"http:\/\/itp4.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-31.png\" alt=\"\" width=\"749\" height=\"694\" \/>\r\n\r\nInput : plaintext block (2w bits length), Key K\r\n\r\n&nbsp;\r\n\r\nProcedure\r\n\r\n&nbsp;\r\n<ol>\r\n \t<li>1. Divide Plaintext block to create two blocks of equal length, LE0 and RE0.<\/li>\r\n \t<li>Perform n rounds, to get the ciphertext block.<\/li>\r\n<\/ol>\r\nEach round is denoted by I having inputs LEi-1 and REi-1 generated\r\n\r\nby the preceding round.\r\n\r\nSubkey Ki is derived from overall K.\r\n\r\n&nbsp;\r\n\r\nRound function F is applied to the right half REi-I , take output and exclusive \u2013 OR with left half and substitute for the right half of REi. LEi will be substituted with REi-1.\r\n\r\n&nbsp;\r\n\r\nLEi = REi-I\r\n\r\n&nbsp;\r\n\r\nREi= LEi-1\u00a0 \u00c5 F(REi-I , Ki)\r\n<ol start=\"3\">\r\n \t<li>Output of the nth round LEn || REn<\/li>\r\n \t<li>Permutation is performed by interchanging two halves of the data and combined. REn ||<\/li>\r\n<\/ol>\r\nLEn\r\n\r\n&nbsp;\r\n\r\n<strong>Strength of Feistel network:<\/strong>\r\n\r\n&nbsp;\r\n\r\nStrength depends on following parameters.\r\n<ul>\r\n \t<li>Block size \u2013 Larger block more security<\/li>\r\n \t<li>Key size \u2013 Larger key size more security<\/li>\r\n \t<li>Number of rounds \u2013 More rounds more security<\/li>\r\n \t<li>Subkey generation algorithm \u2013 complex algorithm- difficult for cryptanalysis to generate key<\/li>\r\n \t<li>Round function F \u2013 complex function , greater resistance to cryptanalysis.<\/li>\r\n<\/ul>\r\n&nbsp;\r\n\r\n<strong>Feistel Cipher Structure \u2013 Decryption:<\/strong>\r\n\r\n&nbsp;\r\n\r\nInput : ciphertext block of length 2w bits\r\n\r\nKey : subkey Ki in reverse order.\r\n\r\nAssuming 16 rounds are performed.\r\n\r\nLDi = RDi-1\r\n\r\n&nbsp;\r\n\r\nRDi = LDi-1 \u00c5 F(RDi-1, Ki)\r\n\r\n&nbsp;\r\n\r\n<strong>Design of Block Cipher:<\/strong>\r\n<ol>\r\n \t<li>Number of Rounds \u2013<\/li>\r\n<\/ol>\r\nMore number of rounds, difficult for cryptanalytic attack.\r\n\r\n&nbsp;\r\n\r\nEven if function F is easy to break, more number of rounds make cipher strength high. 2. Function F design\r\n\r\nF adds confusion. F must be difficult to evaluate through linear equations.\r\n\r\nF must produce avalanche effect. One bit change produces change in several bits.\r\n\r\n&nbsp;\r\n\r\nF must follow bit independence criteria. Bit i is flipped for any i,j,k then output bit j and k should be changed independently.\r\n<ol start=\"3\">\r\n \t<li>Key generation<\/li>\r\n<\/ol>\r\nGenerate one subkey for each round.\r\n\r\nSubkeys should be derived in such way that individual subkeys cannnot be\r\n\r\ndetermined.\r\n\r\nFrom the subkey, one should not be able to derive main key.\r\n\r\n<\/div>\r\n<table>\r\n<tbody>\r\n<tr>\r\n<td><strong>you can view video on Stream ciphers and block ciphers, Feistel cipher<\/strong><\/td>\r\n<td><a href=\"https:\/\/youtu.be\/M8EYofEoMM8\" 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<\/ol>\r\n<a href=\"https:\/\/nmap.org\/\">https:\/\/nmap.org<\/a>\r\n\r\n&nbsp;","rendered":"<div><span style=\"float: right;\"><a href=\"https:\/\/youtu.be\/M8EYofEoMM8\" 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>Stream Ciphers:<\/strong><\/p>\n<ul>\n<li>Stream cipher takes one bit or one byte at a time from digital data and encrypts.<\/li>\n<li>Vernam cipher is an example of stream cipher.<\/li>\n<li>pi = ith digit from binary form of plaintext, Ki = ith digit from binary form of key, ci = ith digit from binary form of ciphertext<\/li>\n<li>\u00c5 = exclusive \u2013 or (XOR) operation<\/li>\n<li>pi=ci \u00c5 ki<\/li>\n<\/ul>\n<p><strong>Block Cipher:<\/strong><\/p>\n<ul>\n<li>Block of plaintext is taken at a time and ciphertext block is produced.<\/li>\n<li>The block is of 64 bits or 128 bits.<\/li>\n<li>The block cipher processes n bits from the plaintext block to produce n bits of a ciphertext block.<\/li>\n<\/ul>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"size-full wp-image-58 aligncenter\" src=\"http:\/\/itp4.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-28.png\" alt=\"\" width=\"917\" height=\"591\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-28.png 917w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-28-300x193.png 300w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-28-768x495.png 768w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-28-65x42.png 65w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-28-225x145.png 225w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-28-350x226.png 350w\" sizes=\"auto, (max-width: 917px) 100vw, 917px\" \/><\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"size-full wp-image-59 aligncenter\" src=\"http:\/\/itp4.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-29.png\" alt=\"\" width=\"923\" height=\"790\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-29.png 923w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-29-300x257.png 300w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-29-768x657.png 768w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-29-65x56.png 65w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-29-225x193.png 225w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-29-350x300.png 350w\" sizes=\"auto, (max-width: 923px) 100vw, 923px\" \/><\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"size-full wp-image-60 aligncenter\" src=\"http:\/\/itp4.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-30.png\" alt=\"\" width=\"795\" height=\"730\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-30.png 795w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-30-300x275.png 300w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-30-768x705.png 768w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-30-65x60.png 65w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-30-225x207.png 225w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-30-350x321.png 350w\" sizes=\"auto, (max-width: 795px) 100vw, 795px\" \/><\/p>\n<p><strong>Problem with Feistel &#8211; Ideal block cipher:<\/strong><\/p>\n<p>&nbsp;<\/p>\n<ul>\n<li>Ideal block cipher is like substitution cipher.<\/li>\n<li>As the block size is small, Vulnerable to statistical analysis.<\/li>\n<li>For large block size , ideal block building implementation and ideal block storing is infeasible.<\/li>\n<li>For 4 bits, 16 rows are needed. Required length of key is 64 bits (4 bits of16 rows). For n bits, nx2n bits.<\/li>\n<li>To prevent statistical attacks, block length must be 64 bits. So requires 64&#215;264 bits.<\/li>\n<li>\n<ul>\n<li>Block cipher having k bits in key and n bits in a block. So 2k possible transformations not 2n!.<strong>Feistel Cipher:<\/strong><\/li>\n<\/ul>\n<ul>\n<li>Feistel suggested to use substitution and permutation alternatively to produce ciphertext.<\/li>\n<\/ul>\n<\/li>\n<li>Substitution- Each plaintext element is replaced by a corresponding element. Replacement is unique.<\/li>\n<li>Permutation -The order of plaintext element is changed.<\/li>\n<\/ul>\n<p><strong>Feistel cipher suggests confusion and diffusion. \u2013 to suppress statistical cryptanalysis:<\/strong><\/p>\n<p>&nbsp;<\/p>\n<ul>\n<li><strong>Diffusion<\/strong><\/li>\n<\/ul>\n<p>One plaintext digit affects in deriving the value of several ciphertext digit. Message M=m1m2m3\u2026. k consecutive letters are added to derive the letter of ciphertext yn<\/p>\n<p>&nbsp;<\/p>\n<p><em>k<\/em><\/p>\n<p><em>y<\/em><em>n<\/em><em>\u00a0 <\/em>= (\u00e5<em>m<\/em><em>n<\/em>+<em>i<\/em> ) mod 26<\/p>\n<p><em>i<\/em>=1<\/p>\n<p>&nbsp;<\/p>\n<p>Statistical relation between plaintext and ciphertext is intricate and it is tricky to derive key.<\/p>\n<p>&nbsp;<\/p>\n<div>\n<p>\u00b7\u00a0\u00a0<strong>Confusion<\/strong><\/p>\n<p>&nbsp;<\/p>\n<p>The statistical relationship between ciphertext and encryption key is so complex that it is difficult to derive key.<\/p>\n<p>&nbsp;<\/p>\n<p>Confusion is created by applying substitution algorithm in complex way.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"size-full wp-image-61 aligncenter\" src=\"http:\/\/itp4.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-31.png\" alt=\"\" width=\"749\" height=\"694\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-31.png 749w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-31-300x278.png 300w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-31-65x60.png 65w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-31-225x208.png 225w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-31-350x324.png 350w\" sizes=\"auto, (max-width: 749px) 100vw, 749px\" \/><\/p>\n<p>Input : plaintext block (2w bits length), Key K<\/p>\n<p>&nbsp;<\/p>\n<p>Procedure<\/p>\n<p>&nbsp;<\/p>\n<ol>\n<li>1. Divide Plaintext block to create two blocks of equal length, LE0 and RE0.<\/li>\n<li>Perform n rounds, to get the ciphertext block.<\/li>\n<\/ol>\n<p>Each round is denoted by I having inputs LEi-1 and REi-1 generated<\/p>\n<p>by the preceding round.<\/p>\n<p>Subkey Ki is derived from overall K.<\/p>\n<p>&nbsp;<\/p>\n<p>Round function F is applied to the right half REi-I , take output and exclusive \u2013 OR with left half and substitute for the right half of REi. LEi will be substituted with REi-1.<\/p>\n<p>&nbsp;<\/p>\n<p>LEi = REi-I<\/p>\n<p>&nbsp;<\/p>\n<p>REi= LEi-1\u00a0 \u00c5 F(REi-I , Ki)<\/p>\n<ol start=\"3\">\n<li>Output of the nth round LEn || REn<\/li>\n<li>Permutation is performed by interchanging two halves of the data and combined. REn ||<\/li>\n<\/ol>\n<p>LEn<\/p>\n<p>&nbsp;<\/p>\n<p><strong>Strength of Feistel network:<\/strong><\/p>\n<p>&nbsp;<\/p>\n<p>Strength depends on following parameters.<\/p>\n<ul>\n<li>Block size \u2013 Larger block more security<\/li>\n<li>Key size \u2013 Larger key size more security<\/li>\n<li>Number of rounds \u2013 More rounds more security<\/li>\n<li>Subkey generation algorithm \u2013 complex algorithm- difficult for cryptanalysis to generate key<\/li>\n<li>Round function F \u2013 complex function , greater resistance to cryptanalysis.<\/li>\n<\/ul>\n<p>&nbsp;<\/p>\n<p><strong>Feistel Cipher Structure \u2013 Decryption:<\/strong><\/p>\n<p>&nbsp;<\/p>\n<p>Input : ciphertext block of length 2w bits<\/p>\n<p>Key : subkey Ki in reverse order.<\/p>\n<p>Assuming 16 rounds are performed.<\/p>\n<p>LDi = RDi-1<\/p>\n<p>&nbsp;<\/p>\n<p>RDi = LDi-1 \u00c5 F(RDi-1, Ki)<\/p>\n<p>&nbsp;<\/p>\n<p><strong>Design of Block Cipher:<\/strong><\/p>\n<ol>\n<li>Number of Rounds \u2013<\/li>\n<\/ol>\n<p>More number of rounds, difficult for cryptanalytic attack.<\/p>\n<p>&nbsp;<\/p>\n<p>Even if function F is easy to break, more number of rounds make cipher strength high. 2. Function F design<\/p>\n<p>F adds confusion. F must be difficult to evaluate through linear equations.<\/p>\n<p>F must produce avalanche effect. One bit change produces change in several bits.<\/p>\n<p>&nbsp;<\/p>\n<p>F must follow bit independence criteria. Bit i is flipped for any i,j,k then output bit j and k should be changed independently.<\/p>\n<ol start=\"3\">\n<li>Key generation<\/li>\n<\/ol>\n<p>Generate one subkey for each round.<\/p>\n<p>Subkeys should be derived in such way that individual subkeys cannnot be<\/p>\n<p>determined.<\/p>\n<p>From the subkey, one should not be able to derive main key.<\/p>\n<\/div>\n<table>\n<tbody>\n<tr>\n<td><strong>you can view video on Stream ciphers and block ciphers, Feistel cipher<\/strong><\/td>\n<td><a href=\"https:\/\/youtu.be\/M8EYofEoMM8\" 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<\/ol>\n<p><a href=\"https:\/\/nmap.org\/\">https:\/\/nmap.org<\/a><\/p>\n<p>&nbsp;<\/p>\n","protected":false},"author":4,"menu_order":5,"template":"","meta":{"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-57","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\/57","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":5,"href":"https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-json\/pressbooks\/v2\/chapters\/57\/revisions"}],"predecessor-version":[{"id":429,"href":"https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-json\/pressbooks\/v2\/chapters\/57\/revisions\/429"}],"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\/57\/metadata\/"}],"wp:attachment":[{"href":"https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-json\/wp\/v2\/media?parent=57"}],"wp:term":[{"taxonomy":"chapter-type","embeddable":true,"href":"https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-json\/pressbooks\/v2\/chapter-type?post=57"},{"taxonomy":"contributor","embeddable":true,"href":"https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-json\/wp\/v2\/contributor?post=57"},{"taxonomy":"license","embeddable":true,"href":"https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-json\/wp\/v2\/license?post=57"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}