{"id":68,"date":"2018-07-11T10:42:06","date_gmt":"2018-07-11T10:42:06","guid":{"rendered":"http:\/\/itp4.epgpbooks.inflibnet.ac.in\/?post_type=chapter&#038;p=68"},"modified":"2019-05-13T11:54:38","modified_gmt":"2019-05-13T11:54:38","slug":"desdata-encryption-standard","status":"publish","type":"chapter","link":"https:\/\/ebooks.inflibnet.ac.in\/itp4\/chapter\/desdata-encryption-standard\/","title":{"rendered":"DES(Data Encryption Standard)"},"content":{"raw":"<div><span style=\"float: right;\"><a href=\"https:\/\/youtu.be\/VdaQc0ERbw8\" 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<ul>\r\n \t<li>\u00a8 DES was issued in 1977by the National Bureau of Standards(Now National Institute of Standards and Technology(NIST))<\/li>\r\n \t<li>\u00a8 In Data Encryption Algorithm, Data is encrypted in the block of 64 bits and key length is 56 bits. The output is of 64 bits.<\/li>\r\n \t<li>\u00a8 For Decryption, the same keys are used in reverse.<\/li>\r\n<\/ul>\r\n<img class=\"size-full wp-image-69 aligncenter\" src=\"http:\/\/itp4.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-33.png\" alt=\"\" width=\"897\" height=\"648\" \/>\r\n<ul>\r\n \t<li>\u00a8 64 bit plaintext passes through an Initial Permutation(IP) . The input bits are rearranged and permuted input is generated.<\/li>\r\n \t<li>\u00a8 Then 16 rounds are performed with same function involving permutation and substitution.<\/li>\r\n \t<li>\u00a8 The output is of 64 bits. The left and right halves are swapped. This swapped output is passed through permutation (IP-1) that is inverse of initial permutation.<\/li>\r\n<\/ul>\r\nKey generation overview\r\n<ul>\r\n \t<li>\u00a8 56 bit key is used. The key is passed through a permutation function.<\/li>\r\n \t<li>\u00a8 For each of the 16 rounds, a subkey(Ki) is produced by the combination of a left circular shift and a permutation.<\/li>\r\n \t<li>\u00a8 For each round, different subkey is generated.<\/li>\r\n<\/ul>\r\nDES works on bits\r\n<ul>\r\n \t<li>\u00a8 DES works in the block of 64 message bits, equal to 16 hexadecimal numbers. DES example<\/li>\r\n<\/ul>\r\nPlaintext :02468aceeca86420\r\n\r\n&nbsp;\r\n\r\nKey :\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 0f1571c947d9e859\r\n\r\nCiphertext :\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 da02ce3a89ecac3b\r\n\r\nSuppose <strong>M being the message:<\/strong>\r\n<ul>\r\n \t<li>\u00a8 <strong>M <\/strong>= 0123456789ABCDEF, represented in hexadecimal.<\/li>\r\n \t<li>\u00a8 The binary form of <strong>M<\/strong> consists 64-bits in one block :<\/li>\r\n \t<li>\u00a8 <strong>M <\/strong>= 0000 0001 0010 0011 0100 0101 0110 0111 1000 1001 1010 1011 1100 1101 1110 1111<\/li>\r\n<\/ul>\r\n<strong>L <\/strong>= 0000 0001 0010 0011 0100 0101 0110 0111<strong> R <\/strong>= 1000 1001 1010 1011 1100 1101 1110 1111\r\n\r\nKey Generation:\r\n\r\n&nbsp;\r\n\r\n<img class=\"size-full wp-image-70 aligncenter\" src=\"http:\/\/itp4.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-34.png\" alt=\"\" width=\"728\" height=\"708\" \/>\r\n<ul>\r\n \t<li>\u00a8 Key <strong>K<\/strong> = 133457799BBCDFF1 represented in hexadecimal.<\/li>\r\n \t<li>\u00a8 <strong>K <\/strong>= 00010011 00110100 01010111 01111001 10011011 10111100 11011111 11110001<\/li>\r\n<\/ul>\r\n<strong>\u00a0 \u00a0 Step 1: Produce 16 subkeys, each 48-bits long.<\/strong>\r\n\r\n<strong>Step 2: Encrypt block of 64-bit.<\/strong>\r\n\r\n<strong>Step 1: Produce 16 subkeys, each 48-bits long.<\/strong>\r\n<ul>\r\n \t<li>\u00a8 Given 64-bit key gets permuted as per table mentioned below:<\/li>\r\n<\/ul>\r\n<img class=\"size-full wp-image-71 aligncenter\" src=\"http:\/\/itp4.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-35.png\" alt=\"\" width=\"855\" height=\"357\" \/>\r\n\r\n&nbsp;\r\n\r\nCheck the table the first entry \"57\" indicates that from the key denoted as K, 57th bit moves as the first bit after permutation and key is denoted as <strong>K<\/strong>+.Given key of length 64-bits\r\n<ul>\r\n \t<li>\u00a8 <strong>K <\/strong>= 00010011 00110100 01010111 01111001 10011011 10111100 11011111 11110001 After permutation 56-bits<\/li>\r\n \t<li>\u00a8 <strong>K<\/strong>+ = 1111000 0110011 0010101 0101111 0101010 1011001 1001111 0001111<\/li>\r\n \t<li>\u00a8 Divide the key to form two parts of 28 bits. Left half denoted by <strong><em>C<\/em><\/strong><strong><em>0<\/em><\/strong> and right halve is denoted by <strong><em>D<\/em><\/strong><strong><em>0<\/em><\/strong>.<\/li>\r\n \t<li>\u00a8 Check <strong>K<\/strong>+,<\/li>\r\n<\/ul>\r\n<strong><em>C<\/em><\/strong><strong><em>0<\/em><\/strong> = 1111000 0110011 0010101 0101111\r\n\r\n<strong><em>D<\/em><\/strong><strong><em>0<\/em><\/strong> = 0101010 1011001 1001111 0001111\r\n<ul>\r\n \t<li>\u00a8 Produce sixteen blocks <strong><em>C<\/em><\/strong><strong><em>n<\/em><\/strong> and <strong><em>D<\/em><\/strong><strong><em>n<\/em><\/strong>, <strong><em>n\u03b5<\/em>[1,<\/strong>16].<\/li>\r\n<\/ul>\r\nEach pair of blocks <strong><em>C<\/em><\/strong><strong><em>n<\/em><\/strong> and <strong><em>D<\/em><\/strong><strong><em>n<\/em><\/strong> is formed from the previous pair <strong><em>C<\/em><\/strong><strong><em>n-1<\/em><\/strong> and <strong><em>D<\/em><\/strong><strong><em>n-1<\/em><\/strong>, respectively, for <strong><em>n<\/em><\/strong> = 1, 2, ..., 16, using the schedule of \"left circular shifts\" of the previous block.\r\n\r\n<img class=\"size-full wp-image-72 aligncenter\" src=\"http:\/\/itp4.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-36.png\" alt=\"\" width=\"439\" height=\"421\" \/>\r\n\r\n<img class=\"size-full wp-image-73 aligncenter\" src=\"http:\/\/itp4.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-37.png\" alt=\"\" width=\"435\" height=\"430\" \/>\r\n<ul>\r\n \t<li>\u00a8 <strong><em>C<\/em><\/strong><strong><em>0<\/em><\/strong> = 1111000011001100101010101111<strong><em> D<\/em><\/strong><strong><em>0<\/em><\/strong> = 0101010101100110011110001111<\/li>\r\n \t<li>\u00a8 <strong><em>C<\/em><\/strong><strong><em>1<\/em><\/strong> = 1110000110011001010101011111<strong><em> D<\/em><\/strong><strong><em>1<\/em><\/strong> = 1010101011001100111100011110<\/li>\r\n \t<li>\u00a8 <strong><em>C<\/em><\/strong><strong><em>2<\/em><\/strong> = 1100001100110010101010111111<strong><em> D<\/em><\/strong><strong><em>2<\/em><\/strong> = 0101010110011001111000111101<\/li>\r\n \t<li>\u00a8 <strong><em>C<\/em><\/strong><strong><em>3<\/em><\/strong> = 0000110011001010101011111111<strong><em> D<\/em><\/strong><strong><em>3<\/em><\/strong> = 0101011001100111100011110101<\/li>\r\n \t<li>\u00a8 <strong><em>C<\/em><\/strong><strong><em>4<\/em><\/strong> = 0011001100101010101111111100<strong><em> D<\/em><\/strong><strong><em>4<\/em><\/strong> = 0101100110011110001111010101<\/li>\r\n \t<li>\u00a8 <strong><em>C<\/em><\/strong><strong><em>5<\/em><\/strong> = 1100110010101010111111110000<strong><em> D<\/em><\/strong><strong><em>5<\/em><\/strong> = 0110011001111000111101010101<\/li>\r\n \t<li>\u00a8 <strong><em>C<\/em><\/strong><strong><em>6<\/em><\/strong> = 0011001010101011111111000011<strong><em> D<\/em><\/strong><strong><em>6<\/em><\/strong> = 1001100111100011110101010101<\/li>\r\n \t<li>\u00a8 <strong><em>C<\/em><\/strong><strong><em>7<\/em><\/strong> = 1100101010101111111100001100<strong><em> D<\/em><\/strong><strong><em>7<\/em><\/strong> = 0110011110001111010101010110<\/li>\r\n \t<li>\u00a8 <strong><em>C<\/em><\/strong><strong><em>8<\/em><\/strong> = 0010101010111111110000110011<strong><em> D<\/em><\/strong><strong><em>8<\/em><\/strong> = 1001111000111101010101011001<\/li>\r\n \t<li>\u00a8 <strong>C<\/strong><strong>16<\/strong> = 1111000011001100101010101111<strong> D<\/strong><strong>16<\/strong> = 0101010101100110011110001111<\/li>\r\n \t<li>\u00a8 <strong>C<\/strong><strong>15<\/strong> = 1111100001100110010101010111<strong> D<\/strong><strong>15<\/strong> = 1010101010110011001111000111<\/li>\r\n \t<li>\u00a8 <strong>C<\/strong><strong>14<\/strong> = 1111111000011001100101010101<strong> D<\/strong><strong>14<\/strong> = 1110101010101100110011110001<\/li>\r\n \t<li>\u00a8 <strong>C<\/strong><strong>13<\/strong> = 0111111110000110011001010101<strong> D<\/strong><strong>13<\/strong> = 0111101010101011001100111100<\/li>\r\n \t<li>\u00a8 <strong>C<\/strong><strong>12<\/strong> = 0101111111100001100110010101<strong> D<\/strong><strong>12<\/strong> = 0001111010101010110011001111<\/li>\r\n \t<li>\u00a8 <strong>C<\/strong><strong>11<\/strong> = 0101011111111000011001100101<strong> D<\/strong><strong>11<\/strong> = 1100011110101010101100110011<\/li>\r\n \t<li>\u00a8 <strong><em>C<\/em><\/strong><strong><em>9<\/em><\/strong> = 0101010101111111100001100110<strong><em> D<\/em><\/strong><strong><em>9<\/em><\/strong> = 0011110001111010101010110011<\/li>\r\n \t<li>\u00a8 <strong>C<\/strong><strong>10<\/strong> = 0101010111111110000110011001<strong> D<\/strong><strong>10<\/strong> = 1111000111101010101011001100\r\n<ul>\r\n \t<li>\u00a8 For each round starting from 1 to 16, the permutation is performed according to table PC-2 and it is applied to pairs formed as <strong><em>C<\/em><\/strong><strong><em>n<\/em><\/strong><strong><em>D<\/em><\/strong><strong><em>n<\/em><\/strong>. Every pair consists of 56 bits, after applying <strong>PC-2<\/strong> 48 bits are generated as shown below:<\/li>\r\n<\/ul>\r\n<\/li>\r\n<\/ul>\r\n<img class=\"size-full wp-image-75 aligncenter\" src=\"http:\/\/itp4.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-39.png\" alt=\"\" width=\"867\" height=\"429\" \/>\r\n\r\n<strong>K<\/strong><strong>2<\/strong> = 011110 011010 111011 011001 110110 111100 100111 100101\r\n\r\n<strong>K<\/strong><strong>3<\/strong> = 010101 011111 110010 001010 010000 101100 111110 011001\r\n\r\n<strong>K<\/strong><strong>4<\/strong> = 011100 101010 110111 010110 110110 110011 010100 011101\r\n\r\n<strong>K<\/strong><strong>5<\/strong> = 011111 001110 110000 000111 111010 110101 001110 101000\r\n\r\n<strong>K<\/strong><strong>6<\/strong> = 011000 111010 010100 111110 010100 000111 101100 101111\r\n\r\n<strong>K<\/strong><strong>7<\/strong> = 111011 001000 010010 110111 111101 100001 100010 111100\r\n\r\n<strong>K<\/strong><strong>8<\/strong> = 111101 111000 101000 111010 110000 010011 101111 111011\r\n\r\n<strong>K<\/strong><strong>9<\/strong> = 111000 001101 101111 101011 111011 011110 011110 000001\r\n\r\n<strong>K<\/strong><strong>10<\/strong> = 101100 011111 001101 000111 101110 100100 011001 001111\r\n\r\n<strong>K<\/strong><strong>11<\/strong> = 001000 010101 111111 010011 110111 101101 001110 000110\r\n\r\n<strong>K<\/strong><strong>12<\/strong> = 011101 010111 000111 110101 100101 000110 011111 101001\r\n\r\n<strong>K<\/strong><strong>13<\/strong> = 100101 111100 010111 010001 111110 101011 101001 000001\r\n\r\n<strong>K<\/strong><strong>14<\/strong> = 010111 110100 001110 110111 111100 101110 011100 111010\r\n\r\n<strong>K<\/strong><strong>15<\/strong> = 101111 111001 000110 001101 001111 010011 111100 001010\r\n\r\n<strong>K<\/strong><strong>16<\/strong> = 110010 110011 110110 001011 000011 100001 011111 110101\r\n\r\n&nbsp;\r\n\r\n<strong>Step 2: Encrypt each data block consisting of 64-bit.<\/strong>\r\n\r\n&nbsp;\r\n<p style=\"text-align: justify\">Initial permutation <strong>IP<\/strong> is applied on the given message M having length of 64 bits. The 58th bit goes as the first bit. Then 50th bit is taken and moved as the second bit. Last bit is the 7th bit of original data<\/p>\r\n&nbsp;\r\n\r\n<img class=\"size-full wp-image-76 aligncenter\" src=\"http:\/\/itp4.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-40.png\" alt=\"\" width=\"663\" height=\"295\" \/>\r\n<ul>\r\n \t<li>\u00a8 After applying the initial permutation,<\/li>\r\n \t<li>\u00a8 <strong>M <\/strong>= 0000 0001 0010 0011 0100 0101 0110 0111 1000 1001 1010 1011 1100 1101 1110 1111<\/li>\r\n<\/ul>\r\n&nbsp;\r\n\r\n<strong>After applying IP,<\/strong>\r\n\r\n&nbsp;\r\n\r\n1100 1100 0000 0000 1100 1100 1111 1111 1111 0000 1010 1010 1111 0000 1010 1010\r\n\r\n&nbsp;\r\n<ul>\r\n \t<li>\u00a8 After permutation separate left 32 bits denote as <strong><em>L<\/em><\/strong><strong><em>0<\/em><\/strong>, and a right 32 bits denote as <strong><em>R<\/em><\/strong><strong><em>0<\/em><\/strong>.<\/li>\r\n \t<li>\u00a8 <strong><em>L<\/em><\/strong><strong><em>0<\/em><\/strong> = 1100 1100 0000 0000 1100 1100 1111 1111<strong><em> R<\/em><\/strong><strong><em>0<\/em><\/strong> = 1111 0000 1010 1010 1111 0000 1010 1010<\/li>\r\n \t<li>\u00a8 16 iterations are performed. 1&lt;=<strong><em>n<\/em><\/strong>&lt;=16. 32 bits data block and a 48 bits key <strong><em>K<\/em><\/strong><strong><em>n<\/em><\/strong> produces a 32 bits block.<\/li>\r\n<\/ul>\r\n&nbsp;\r\n\r\nGenerate <em>L<\/em><em>n<\/em> and <em>R<\/em><em>n<\/em>\r\n<ul>\r\n \t<li>\u00a8 Consider + as XOR addition,<\/li>\r\n \t<li>\u00a8 Ln = Rn-1\u00a0 \u00a0Rn = Ln-1 + f(Rn-1,Kn)<\/li>\r\n \t<li>\u00a8 for n = 16, the block produced is L16R1<strong style=\"text-align: initial;font-size: 1em\"><em>6<\/em><\/strong><span style=\"text-align: initial;font-size: 1em\">. Consider <\/span><strong style=\"text-align: initial;font-size: 1em\"><em>n<\/em><\/strong><span style=\"text-align: initial;font-size: 1em\"> = 1,<\/span><\/li>\r\n \t<li>\u00a8 <strong><em>K<\/em><\/strong><strong><em>1<\/em><\/strong> = 000110 110000 001011 101111 111111 000111 000001 110010<strong><em> L<\/em><\/strong><strong><em>1<\/em><\/strong> =<strong><em> R<\/em><\/strong><strong><em>0<\/em><\/strong> = 1111 0000 1010 1010 1111 0000 1010 1010<\/li>\r\n<\/ul>\r\n&nbsp;\r\n\r\n<strong><em>R<\/em><\/strong><strong><em>1<\/em><\/strong> =<strong><em> L<\/em><\/strong><strong><em>0<\/em><\/strong> +<strong><em> f<\/em><\/strong>(<strong><em>R<\/em><\/strong><strong><em>0<\/em><\/strong>,<strong><em>K<\/em><\/strong><strong><em>1<\/em><\/strong>)\r\n\r\n&nbsp;\r\n\r\nHow function f works?\r\n<ul>\r\n \t<li>\u00a8 In first step, every <strong><em>R<\/em><\/strong><strong><em>n-1<\/em><\/strong> gets expanded to 48 bits from 32 bits. For that some bits need to be repeated in <strong><em>R<\/em><\/strong><strong><em>n-1<\/em><\/strong> .<\/li>\r\n \t<li>\u00a8 Use the expand table. Thus <strong>E<\/strong>(<strong><em>R<\/em><\/strong><strong><em>n-1<\/em><\/strong>) has input as clock of 32 bits, and output as block of 48 bits.<\/li>\r\n \t<li><\/li>\r\n \t<li><img class=\"size-full wp-image-77 aligncenter\" src=\"http:\/\/itp4.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-41.png\" alt=\"\" width=\"621\" height=\"440\" \/><\/li>\r\n \t<li>\u00a8 <strong>E<\/strong>(<strong><em>R<\/em><\/strong><strong><em>0<\/em><\/strong>) is:<\/li>\r\n \t<li>\u00a8 <strong><em>R<\/em><\/strong><strong><em>0 <\/em><\/strong>= 1111 0000 1010 1010 1111 0000 1010 1010<\/li>\r\n<\/ul>\r\n<strong>E<\/strong>(<strong><em>R<\/em><\/strong><strong><em>0<\/em><\/strong>) = 011110 100001 010101 010101 011110 100001 010101 010101\r\n<ul>\r\n \t<li>\u00a8 For function <strong><em>f,<\/em><\/strong> generated bits of <strong>E<\/strong>(<strong><em>R<\/em><\/strong><strong><em>n-1<\/em><\/strong>) and <strong><em>K<\/em><\/strong><strong><em>n<\/em><\/strong> (key pertaining to the round) are XORed.<\/li>\r\n \t<li>\u00a8 <strong><em>K<\/em><\/strong><strong><em>n <\/em><\/strong>+<strong> E<\/strong>(<strong><em>R<\/em><\/strong><strong><em>n-1<\/em><\/strong>).<\/li>\r\n<\/ul>\r\n<img class=\"size-full wp-image-78 aligncenter\" src=\"http:\/\/itp4.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-42.png\" alt=\"\" width=\"726\" height=\"274\" \/>\r\n<ul>\r\n \t<li>\u00a8 Out of 48 bits, Form 8 groups consisting of 6 bits. These 6 bits forms combination of row and column in \"S boxes\". For every group there is a separate S box. A 4 bit number is stored at the intersection of row and column. The new 4 bits replace the 6 bits and all eight groups form 32 bits.<\/li>\r\n \t<li>\u00a8 Kn + E(Rn-1) =B1B2B3B4B5B6B7B8, All Bi comprises of 6 bits.<\/li>\r\n \t<li>\u00a8 S1(B1)S2(B2)S3(B3)S4(B4)S5(B5)S6(B6)S7(B7)S8(B8)<\/li>\r\n<\/ul>\r\nwhere Si(Bi) refers to the i-th S box.\r\n<ul>\r\n \t<li>\u00a8 <strong><em>S<\/em><\/strong><strong><em>1<\/em><\/strong><strong><em>, S<\/em><\/strong><strong><em>2<\/em><\/strong><strong><em>,..., S<\/em><\/strong><strong><em>8<\/em><\/strong>, has input of 6-bits and generates a 4-bit block.<\/li>\r\n \t<li>\u00a8 <strong><em>S<\/em><\/strong><strong><em>1(B) <\/em><\/strong>works as follows:<\/li>\r\n<\/ul>\r\n<p style=\"text-align: justify\">The first bit combined with last bit in block <strong><em>B<\/em><\/strong> represents(00,01,10,11) in binary correspondingly 0,1,2,3 in decimal represented as <strong><em>i<\/em><\/strong>. The middle 4 bits of <strong><em>B<\/em><\/strong> corresponds to 0 to 15 in decimal (binary 0000 to 1111) represented as <strong><em>j<\/em><\/strong>. Check the corresponding S box for intersection of the row(ith in this case) with column(<strong><em>j<\/em><\/strong>-th in this case), the number is between 0 to 15 and can be depicted as a 4 bit block considered as <strong><em>S<\/em><\/strong><strong><em>1<\/em><\/strong><strong><em>(B)<\/em><\/strong> output .<\/p>\r\n&nbsp;\r\n<p style=\"text-align: justify\">For example block <strong><em>B<\/em><\/strong> = 011100 as input. \"0\" is the first bit and \u201c0\u201d is the last bit producing 00 for the row lookup. The in between four bits are \"1110\" equivalent to decimal 14.So lookup in column number 14. In row 0, column 14 the value stored is 0 in binary 0000. Hence <strong><em>S<\/em><\/strong><strong><em>1<\/em><\/strong>(011011) = 0000.<\/p>\r\n&nbsp;\r\n\r\n<img class=\"size-full wp-image-79 aligncenter\" src=\"http:\/\/itp4.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-43.png\" alt=\"\" width=\"851\" height=\"390\" \/>\r\n\r\n<img class=\"size-full wp-image-80 aligncenter\" src=\"http:\/\/itp4.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-44.png\" alt=\"\" width=\"850\" height=\"509\" \/>\r\n\r\n<img class=\"size-full wp-image-81 aligncenter\" src=\"http:\/\/itp4.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-45.png\" alt=\"\" width=\"890\" height=\"404\" \/>\r\n\r\n<img class=\"size-full wp-image-82 aligncenter\" src=\"http:\/\/itp4.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-46.png\" alt=\"\" width=\"816\" height=\"801\" \/>\r\n\r\n<img class=\"size-full wp-image-83 aligncenter\" src=\"http:\/\/itp4.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-47.png\" alt=\"\" width=\"883\" height=\"819\" \/>\r\n\r\n<img class=\"size-full wp-image-84 aligncenter\" src=\"http:\/\/itp4.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-48.png\" alt=\"\" width=\"818\" height=\"830\" \/>\r\n\r\n&nbsp;\r\n\r\n&nbsp;\r\n\r\n<img class=\"size-full wp-image-85 aligncenter\" src=\"http:\/\/itp4.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-49.png\" alt=\"\" width=\"833\" height=\"368\" \/>\r\n<ul>\r\n \t<li>\u00a8 The binary <em>output<\/em> 011000 010001 011110 111010 100001 100110 010100 100111. <em>results in <\/em>0101 1100 1000 0010 1011 0101 1001 0111 after passing through S-box.<\/li>\r\n \t<li>\u00a8 The last step is to permute output of S-box:<\/li>\r\n<\/ul>\r\nThe permutation is applied as per table <strong>P<\/strong>. Input is of 32-bit and output is of 32-bit.\r\n<ul>\r\n \t<li>\u00a8 <strong>P<\/strong><\/li>\r\n<\/ul>\r\n<img class=\"size-full wp-image-86 aligncenter\" src=\"http:\/\/itp4.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-50.png\" alt=\"\" width=\"683\" height=\"520\" \/>\r\n<ul>\r\n \t<li style=\"text-align: justify\">\u00a8 = 1100 1100 0000 0000 1100 1100 1111 1111 + 0010 0011 0100 1010 1010 1001 1011 1011 = 1110 1111 0100 1010 0110 0101 0100 0100<\/li>\r\n \t<li>\u00a8 For the second round, assign L2 = R1 and compute R2 =L1 + f(R1, K2), and repeat till round 16.<\/li>\r\n \t<li style=\"text-align: justify\">\u00a8 After round sixteen, L16 and R16 are generated. The order is reversed to generate the 64-bit block R16L16<\/li>\r\n \t<li>\u00a8 Finally <strong>IP<\/strong><strong>-1<\/strong> is applied for permutation<\/li>\r\n<\/ul>\r\n<img class=\"size-full wp-image-87 aligncenter\" src=\"http:\/\/itp4.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-51.png\" alt=\"\" width=\"614\" height=\"412\" \/>\r\n\r\nBit 40 takes first bit position, bit 8 takes second bit position, until bit 25 occupies last position.\r\n\r\n&nbsp;\r\n\r\nAt the end of round 16:\r\n\r\n&nbsp;\r\n\r\nL16 = 0100 0011 0100 0010 0011 0010 0011 0100\r\n\r\nR16 = 0000 1010 0100 1100 1101 1001 1001 0101\r\n\r\nOrder must be reversed and the final permutation must be applied:\r\n\r\nR16L16 = 00001010 01001100 11011001 10010101 01000011 01000010 00110010 00110100\r\n\r\nIP-1 = 10000101 11101000 00010011 01010100 00001111 00001010 10110100 00000101\r\n\r\nConvert to hexadecimal:\r\n\r\n85E813540F0AB405.\r\n\r\nGiven M = 0123456789ABCDEF, encryption C = 85E813540F0AB405.\r\n\r\n&nbsp;\r\n\r\nDecryption:\r\n\r\n&nbsp;\r\n\r\nDecryption, inverse operation of encryption follows steps similar to encrytion, but keys are applied in the reverse way.\r\n\r\n&nbsp;\r\n\r\nThe Strength of DES\r\n<ul>\r\n \t<li>\u00a8 The use of 56-Bit keys.<\/li>\r\n \t<li>n 256 possible keys so brute force attack is impractical.<\/li>\r\n \t<li>\u00a8 The Nature of the DES algorithm.<\/li>\r\n \t<li>n Design criteria for S-boxes were not made public. No one has been successful in finding weakness in S-box.<\/li>\r\n \t<li>\u00a8 Timing attacks.<\/li>\r\n \t<li style=\"text-align: justify\">n Timing attack exploits that encryption and decryption algorithm takes slightly different amounts of time on different inputs.<\/li>\r\n<\/ul>\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;\r\n<table>\r\n<tbody>\r\n<tr>\r\n<td><strong>you can view video on DES(Data Encryption Standard)<\/strong><\/td>\r\n<td><a href=\"https:\/\/youtu.be\/VdaQc0ERbw8\" 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&nbsp;","rendered":"<div><span style=\"float: right;\"><a href=\"https:\/\/youtu.be\/VdaQc0ERbw8\" 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<ul>\n<li>\u00a8 DES was issued in 1977by the National Bureau of Standards(Now National Institute of Standards and Technology(NIST))<\/li>\n<li>\u00a8 In Data Encryption Algorithm, Data is encrypted in the block of 64 bits and key length is 56 bits. The output is of 64 bits.<\/li>\n<li>\u00a8 For Decryption, the same keys are used in reverse.<\/li>\n<\/ul>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"size-full wp-image-69 aligncenter\" src=\"http:\/\/itp4.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-33.png\" alt=\"\" width=\"897\" height=\"648\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-33.png 897w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-33-300x217.png 300w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-33-768x555.png 768w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-33-65x47.png 65w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-33-225x163.png 225w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-33-350x253.png 350w\" sizes=\"auto, (max-width: 897px) 100vw, 897px\" \/><\/p>\n<ul>\n<li>\u00a8 64 bit plaintext passes through an Initial Permutation(IP) . The input bits are rearranged and permuted input is generated.<\/li>\n<li>\u00a8 Then 16 rounds are performed with same function involving permutation and substitution.<\/li>\n<li>\u00a8 The output is of 64 bits. The left and right halves are swapped. This swapped output is passed through permutation (IP-1) that is inverse of initial permutation.<\/li>\n<\/ul>\n<p>Key generation overview<\/p>\n<ul>\n<li>\u00a8 56 bit key is used. The key is passed through a permutation function.<\/li>\n<li>\u00a8 For each of the 16 rounds, a subkey(Ki) is produced by the combination of a left circular shift and a permutation.<\/li>\n<li>\u00a8 For each round, different subkey is generated.<\/li>\n<\/ul>\n<p>DES works on bits<\/p>\n<ul>\n<li>\u00a8 DES works in the block of 64 message bits, equal to 16 hexadecimal numbers. DES example<\/li>\n<\/ul>\n<p>Plaintext :02468aceeca86420<\/p>\n<p>&nbsp;<\/p>\n<p>Key :\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 0f1571c947d9e859<\/p>\n<p>Ciphertext :\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 da02ce3a89ecac3b<\/p>\n<p>Suppose <strong>M being the message:<\/strong><\/p>\n<ul>\n<li>\u00a8 <strong>M <\/strong>= 0123456789ABCDEF, represented in hexadecimal.<\/li>\n<li>\u00a8 The binary form of <strong>M<\/strong> consists 64-bits in one block :<\/li>\n<li>\u00a8 <strong>M <\/strong>= 0000 0001 0010 0011 0100 0101 0110 0111 1000 1001 1010 1011 1100 1101 1110 1111<\/li>\n<\/ul>\n<p><strong>L <\/strong>= 0000 0001 0010 0011 0100 0101 0110 0111<strong> R <\/strong>= 1000 1001 1010 1011 1100 1101 1110 1111<\/p>\n<p>Key Generation:<\/p>\n<p>&nbsp;<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"size-full wp-image-70 aligncenter\" src=\"http:\/\/itp4.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-34.png\" alt=\"\" width=\"728\" height=\"708\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-34.png 728w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-34-300x292.png 300w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-34-65x63.png 65w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-34-225x219.png 225w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-34-350x340.png 350w\" sizes=\"auto, (max-width: 728px) 100vw, 728px\" \/><\/p>\n<ul>\n<li>\u00a8 Key <strong>K<\/strong> = 133457799BBCDFF1 represented in hexadecimal.<\/li>\n<li>\u00a8 <strong>K <\/strong>= 00010011 00110100 01010111 01111001 10011011 10111100 11011111 11110001<\/li>\n<\/ul>\n<p><strong>\u00a0 \u00a0 Step 1: Produce 16 subkeys, each 48-bits long.<\/strong><\/p>\n<p><strong>Step 2: Encrypt block of 64-bit.<\/strong><\/p>\n<p><strong>Step 1: Produce 16 subkeys, each 48-bits long.<\/strong><\/p>\n<ul>\n<li>\u00a8 Given 64-bit key gets permuted as per table mentioned below:<\/li>\n<\/ul>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"size-full wp-image-71 aligncenter\" src=\"http:\/\/itp4.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-35.png\" alt=\"\" width=\"855\" height=\"357\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-35.png 855w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-35-300x125.png 300w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-35-768x321.png 768w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-35-65x27.png 65w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-35-225x94.png 225w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-35-350x146.png 350w\" sizes=\"auto, (max-width: 855px) 100vw, 855px\" \/><\/p>\n<p>&nbsp;<\/p>\n<p>Check the table the first entry &#8220;57&#8221; indicates that from the key denoted as K, 57th bit moves as the first bit after permutation and key is denoted as <strong>K<\/strong>+.Given key of length 64-bits<\/p>\n<ul>\n<li>\u00a8 <strong>K <\/strong>= 00010011 00110100 01010111 01111001 10011011 10111100 11011111 11110001 After permutation 56-bits<\/li>\n<li>\u00a8 <strong>K<\/strong>+ = 1111000 0110011 0010101 0101111 0101010 1011001 1001111 0001111<\/li>\n<li>\u00a8 Divide the key to form two parts of 28 bits. Left half denoted by <strong><em>C<\/em><\/strong><strong><em>0<\/em><\/strong> and right halve is denoted by <strong><em>D<\/em><\/strong><strong><em>0<\/em><\/strong>.<\/li>\n<li>\u00a8 Check <strong>K<\/strong>+,<\/li>\n<\/ul>\n<p><strong><em>C<\/em><\/strong><strong><em>0<\/em><\/strong> = 1111000 0110011 0010101 0101111<\/p>\n<p><strong><em>D<\/em><\/strong><strong><em>0<\/em><\/strong> = 0101010 1011001 1001111 0001111<\/p>\n<ul>\n<li>\u00a8 Produce sixteen blocks <strong><em>C<\/em><\/strong><strong><em>n<\/em><\/strong> and <strong><em>D<\/em><\/strong><strong><em>n<\/em><\/strong>, <strong><em>n\u03b5<\/em>[1,<\/strong>16].<\/li>\n<\/ul>\n<p>Each pair of blocks <strong><em>C<\/em><\/strong><strong><em>n<\/em><\/strong> and <strong><em>D<\/em><\/strong><strong><em>n<\/em><\/strong> is formed from the previous pair <strong><em>C<\/em><\/strong><strong><em>n-1<\/em><\/strong> and <strong><em>D<\/em><\/strong><strong><em>n-1<\/em><\/strong>, respectively, for <strong><em>n<\/em><\/strong> = 1, 2, &#8230;, 16, using the schedule of &#8220;left circular shifts&#8221; of the previous block.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"size-full wp-image-72 aligncenter\" src=\"http:\/\/itp4.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-36.png\" alt=\"\" width=\"439\" height=\"421\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-36.png 439w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-36-300x288.png 300w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-36-65x62.png 65w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-36-225x216.png 225w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-36-350x336.png 350w\" sizes=\"auto, (max-width: 439px) 100vw, 439px\" \/><\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"size-full wp-image-73 aligncenter\" src=\"http:\/\/itp4.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-37.png\" alt=\"\" width=\"435\" height=\"430\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-37.png 435w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-37-300x297.png 300w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-37-65x64.png 65w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-37-225x222.png 225w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-37-350x346.png 350w\" sizes=\"auto, (max-width: 435px) 100vw, 435px\" \/><\/p>\n<ul>\n<li>\u00a8 <strong><em>C<\/em><\/strong><strong><em>0<\/em><\/strong> = 1111000011001100101010101111<strong><em> D<\/em><\/strong><strong><em>0<\/em><\/strong> = 0101010101100110011110001111<\/li>\n<li>\u00a8 <strong><em>C<\/em><\/strong><strong><em>1<\/em><\/strong> = 1110000110011001010101011111<strong><em> D<\/em><\/strong><strong><em>1<\/em><\/strong> = 1010101011001100111100011110<\/li>\n<li>\u00a8 <strong><em>C<\/em><\/strong><strong><em>2<\/em><\/strong> = 1100001100110010101010111111<strong><em> D<\/em><\/strong><strong><em>2<\/em><\/strong> = 0101010110011001111000111101<\/li>\n<li>\u00a8 <strong><em>C<\/em><\/strong><strong><em>3<\/em><\/strong> = 0000110011001010101011111111<strong><em> D<\/em><\/strong><strong><em>3<\/em><\/strong> = 0101011001100111100011110101<\/li>\n<li>\u00a8 <strong><em>C<\/em><\/strong><strong><em>4<\/em><\/strong> = 0011001100101010101111111100<strong><em> D<\/em><\/strong><strong><em>4<\/em><\/strong> = 0101100110011110001111010101<\/li>\n<li>\u00a8 <strong><em>C<\/em><\/strong><strong><em>5<\/em><\/strong> = 1100110010101010111111110000<strong><em> D<\/em><\/strong><strong><em>5<\/em><\/strong> = 0110011001111000111101010101<\/li>\n<li>\u00a8 <strong><em>C<\/em><\/strong><strong><em>6<\/em><\/strong> = 0011001010101011111111000011<strong><em> D<\/em><\/strong><strong><em>6<\/em><\/strong> = 1001100111100011110101010101<\/li>\n<li>\u00a8 <strong><em>C<\/em><\/strong><strong><em>7<\/em><\/strong> = 1100101010101111111100001100<strong><em> D<\/em><\/strong><strong><em>7<\/em><\/strong> = 0110011110001111010101010110<\/li>\n<li>\u00a8 <strong><em>C<\/em><\/strong><strong><em>8<\/em><\/strong> = 0010101010111111110000110011<strong><em> D<\/em><\/strong><strong><em>8<\/em><\/strong> = 1001111000111101010101011001<\/li>\n<li>\u00a8 <strong>C<\/strong><strong>16<\/strong> = 1111000011001100101010101111<strong> D<\/strong><strong>16<\/strong> = 0101010101100110011110001111<\/li>\n<li>\u00a8 <strong>C<\/strong><strong>15<\/strong> = 1111100001100110010101010111<strong> D<\/strong><strong>15<\/strong> = 1010101010110011001111000111<\/li>\n<li>\u00a8 <strong>C<\/strong><strong>14<\/strong> = 1111111000011001100101010101<strong> D<\/strong><strong>14<\/strong> = 1110101010101100110011110001<\/li>\n<li>\u00a8 <strong>C<\/strong><strong>13<\/strong> = 0111111110000110011001010101<strong> D<\/strong><strong>13<\/strong> = 0111101010101011001100111100<\/li>\n<li>\u00a8 <strong>C<\/strong><strong>12<\/strong> = 0101111111100001100110010101<strong> D<\/strong><strong>12<\/strong> = 0001111010101010110011001111<\/li>\n<li>\u00a8 <strong>C<\/strong><strong>11<\/strong> = 0101011111111000011001100101<strong> D<\/strong><strong>11<\/strong> = 1100011110101010101100110011<\/li>\n<li>\u00a8 <strong><em>C<\/em><\/strong><strong><em>9<\/em><\/strong> = 0101010101111111100001100110<strong><em> D<\/em><\/strong><strong><em>9<\/em><\/strong> = 0011110001111010101010110011<\/li>\n<li>\u00a8 <strong>C<\/strong><strong>10<\/strong> = 0101010111111110000110011001<strong> D<\/strong><strong>10<\/strong> = 1111000111101010101011001100\n<ul>\n<li>\u00a8 For each round starting from 1 to 16, the permutation is performed according to table PC-2 and it is applied to pairs formed as <strong><em>C<\/em><\/strong><strong><em>n<\/em><\/strong><strong><em>D<\/em><\/strong><strong><em>n<\/em><\/strong>. Every pair consists of 56 bits, after applying <strong>PC-2<\/strong> 48 bits are generated as shown below:<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"size-full wp-image-75 aligncenter\" src=\"http:\/\/itp4.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-39.png\" alt=\"\" width=\"867\" height=\"429\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-39.png 867w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-39-300x148.png 300w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-39-768x380.png 768w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-39-65x32.png 65w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-39-225x111.png 225w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-39-350x173.png 350w\" sizes=\"auto, (max-width: 867px) 100vw, 867px\" \/><\/p>\n<p><strong>K<\/strong><strong>2<\/strong> = 011110 011010 111011 011001 110110 111100 100111 100101<\/p>\n<p><strong>K<\/strong><strong>3<\/strong> = 010101 011111 110010 001010 010000 101100 111110 011001<\/p>\n<p><strong>K<\/strong><strong>4<\/strong> = 011100 101010 110111 010110 110110 110011 010100 011101<\/p>\n<p><strong>K<\/strong><strong>5<\/strong> = 011111 001110 110000 000111 111010 110101 001110 101000<\/p>\n<p><strong>K<\/strong><strong>6<\/strong> = 011000 111010 010100 111110 010100 000111 101100 101111<\/p>\n<p><strong>K<\/strong><strong>7<\/strong> = 111011 001000 010010 110111 111101 100001 100010 111100<\/p>\n<p><strong>K<\/strong><strong>8<\/strong> = 111101 111000 101000 111010 110000 010011 101111 111011<\/p>\n<p><strong>K<\/strong><strong>9<\/strong> = 111000 001101 101111 101011 111011 011110 011110 000001<\/p>\n<p><strong>K<\/strong><strong>10<\/strong> = 101100 011111 001101 000111 101110 100100 011001 001111<\/p>\n<p><strong>K<\/strong><strong>11<\/strong> = 001000 010101 111111 010011 110111 101101 001110 000110<\/p>\n<p><strong>K<\/strong><strong>12<\/strong> = 011101 010111 000111 110101 100101 000110 011111 101001<\/p>\n<p><strong>K<\/strong><strong>13<\/strong> = 100101 111100 010111 010001 111110 101011 101001 000001<\/p>\n<p><strong>K<\/strong><strong>14<\/strong> = 010111 110100 001110 110111 111100 101110 011100 111010<\/p>\n<p><strong>K<\/strong><strong>15<\/strong> = 101111 111001 000110 001101 001111 010011 111100 001010<\/p>\n<p><strong>K<\/strong><strong>16<\/strong> = 110010 110011 110110 001011 000011 100001 011111 110101<\/p>\n<p>&nbsp;<\/p>\n<p><strong>Step 2: Encrypt each data block consisting of 64-bit.<\/strong><\/p>\n<p>&nbsp;<\/p>\n<p style=\"text-align: justify\">Initial permutation <strong>IP<\/strong> is applied on the given message M having length of 64 bits. The 58th bit goes as the first bit. Then 50th bit is taken and moved as the second bit. Last bit is the 7th bit of original data<\/p>\n<p>&nbsp;<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"size-full wp-image-76 aligncenter\" src=\"http:\/\/itp4.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-40.png\" alt=\"\" width=\"663\" height=\"295\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-40.png 663w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-40-300x133.png 300w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-40-65x29.png 65w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-40-225x100.png 225w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-40-350x156.png 350w\" sizes=\"auto, (max-width: 663px) 100vw, 663px\" \/><\/p>\n<ul>\n<li>\u00a8 After applying the initial permutation,<\/li>\n<li>\u00a8 <strong>M <\/strong>= 0000 0001 0010 0011 0100 0101 0110 0111 1000 1001 1010 1011 1100 1101 1110 1111<\/li>\n<\/ul>\n<p>&nbsp;<\/p>\n<p><strong>After applying IP,<\/strong><\/p>\n<p>&nbsp;<\/p>\n<p>1100 1100 0000 0000 1100 1100 1111 1111 1111 0000 1010 1010 1111 0000 1010 1010<\/p>\n<p>&nbsp;<\/p>\n<ul>\n<li>\u00a8 After permutation separate left 32 bits denote as <strong><em>L<\/em><\/strong><strong><em>0<\/em><\/strong>, and a right 32 bits denote as <strong><em>R<\/em><\/strong><strong><em>0<\/em><\/strong>.<\/li>\n<li>\u00a8 <strong><em>L<\/em><\/strong><strong><em>0<\/em><\/strong> = 1100 1100 0000 0000 1100 1100 1111 1111<strong><em> R<\/em><\/strong><strong><em>0<\/em><\/strong> = 1111 0000 1010 1010 1111 0000 1010 1010<\/li>\n<li>\u00a8 16 iterations are performed. 1&lt;=<strong><em>n<\/em><\/strong>&lt;=16. 32 bits data block and a 48 bits key <strong><em>K<\/em><\/strong><strong><em>n<\/em><\/strong> produces a 32 bits block.<\/li>\n<\/ul>\n<p>&nbsp;<\/p>\n<p>Generate <em>L<\/em><em>n<\/em> and <em>R<\/em><em>n<\/em><\/p>\n<ul>\n<li>\u00a8 Consider + as XOR addition,<\/li>\n<li>\u00a8 Ln = Rn-1\u00a0 \u00a0Rn = Ln-1 + f(Rn-1,Kn)<\/li>\n<li>\u00a8 for n = 16, the block produced is L16R1<strong style=\"text-align: initial;font-size: 1em\"><em>6<\/em><\/strong><span style=\"text-align: initial;font-size: 1em\">. Consider <\/span><strong style=\"text-align: initial;font-size: 1em\"><em>n<\/em><\/strong><span style=\"text-align: initial;font-size: 1em\"> = 1,<\/span><\/li>\n<li>\u00a8 <strong><em>K<\/em><\/strong><strong><em>1<\/em><\/strong> = 000110 110000 001011 101111 111111 000111 000001 110010<strong><em> L<\/em><\/strong><strong><em>1<\/em><\/strong> =<strong><em> R<\/em><\/strong><strong><em>0<\/em><\/strong> = 1111 0000 1010 1010 1111 0000 1010 1010<\/li>\n<\/ul>\n<p>&nbsp;<\/p>\n<p><strong><em>R<\/em><\/strong><strong><em>1<\/em><\/strong> =<strong><em> L<\/em><\/strong><strong><em>0<\/em><\/strong> +<strong><em> f<\/em><\/strong>(<strong><em>R<\/em><\/strong><strong><em>0<\/em><\/strong>,<strong><em>K<\/em><\/strong><strong><em>1<\/em><\/strong>)<\/p>\n<p>&nbsp;<\/p>\n<p>How function f works?<\/p>\n<ul>\n<li>\u00a8 In first step, every <strong><em>R<\/em><\/strong><strong><em>n-1<\/em><\/strong> gets expanded to 48 bits from 32 bits. For that some bits need to be repeated in <strong><em>R<\/em><\/strong><strong><em>n-1<\/em><\/strong> .<\/li>\n<li>\u00a8 Use the expand table. Thus <strong>E<\/strong>(<strong><em>R<\/em><\/strong><strong><em>n-1<\/em><\/strong>) has input as clock of 32 bits, and output as block of 48 bits.<\/li>\n<li><\/li>\n<li><img loading=\"lazy\" decoding=\"async\" class=\"size-full wp-image-77 aligncenter\" src=\"http:\/\/itp4.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-41.png\" alt=\"\" width=\"621\" height=\"440\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-41.png 621w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-41-300x213.png 300w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-41-65x46.png 65w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-41-225x159.png 225w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-41-350x248.png 350w\" sizes=\"auto, (max-width: 621px) 100vw, 621px\" \/><\/li>\n<li>\u00a8 <strong>E<\/strong>(<strong><em>R<\/em><\/strong><strong><em>0<\/em><\/strong>) is:<\/li>\n<li>\u00a8 <strong><em>R<\/em><\/strong><strong><em>0 <\/em><\/strong>= 1111 0000 1010 1010 1111 0000 1010 1010<\/li>\n<\/ul>\n<p><strong>E<\/strong>(<strong><em>R<\/em><\/strong><strong><em>0<\/em><\/strong>) = 011110 100001 010101 010101 011110 100001 010101 010101<\/p>\n<ul>\n<li>\u00a8 For function <strong><em>f,<\/em><\/strong> generated bits of <strong>E<\/strong>(<strong><em>R<\/em><\/strong><strong><em>n-1<\/em><\/strong>) and <strong><em>K<\/em><\/strong><strong><em>n<\/em><\/strong> (key pertaining to the round) are XORed.<\/li>\n<li>\u00a8 <strong><em>K<\/em><\/strong><strong><em>n <\/em><\/strong>+<strong> E<\/strong>(<strong><em>R<\/em><\/strong><strong><em>n-1<\/em><\/strong>).<\/li>\n<\/ul>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"size-full wp-image-78 aligncenter\" src=\"http:\/\/itp4.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-42.png\" alt=\"\" width=\"726\" height=\"274\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-42.png 726w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-42-300x113.png 300w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-42-65x25.png 65w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-42-225x85.png 225w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-42-350x132.png 350w\" sizes=\"auto, (max-width: 726px) 100vw, 726px\" \/><\/p>\n<ul>\n<li>\u00a8 Out of 48 bits, Form 8 groups consisting of 6 bits. These 6 bits forms combination of row and column in &#8220;S boxes&#8221;. For every group there is a separate S box. A 4 bit number is stored at the intersection of row and column. The new 4 bits replace the 6 bits and all eight groups form 32 bits.<\/li>\n<li>\u00a8 Kn + E(Rn-1) =B1B2B3B4B5B6B7B8, All Bi comprises of 6 bits.<\/li>\n<li>\u00a8 S1(B1)S2(B2)S3(B3)S4(B4)S5(B5)S6(B6)S7(B7)S8(B8)<\/li>\n<\/ul>\n<p>where Si(Bi) refers to the i-th S box.<\/p>\n<ul>\n<li>\u00a8 <strong><em>S<\/em><\/strong><strong><em>1<\/em><\/strong><strong><em>, S<\/em><\/strong><strong><em>2<\/em><\/strong><strong><em>,&#8230;, S<\/em><\/strong><strong><em>8<\/em><\/strong>, has input of 6-bits and generates a 4-bit block.<\/li>\n<li>\u00a8 <strong><em>S<\/em><\/strong><strong><em>1(B) <\/em><\/strong>works as follows:<\/li>\n<\/ul>\n<p style=\"text-align: justify\">The first bit combined with last bit in block <strong><em>B<\/em><\/strong> represents(00,01,10,11) in binary correspondingly 0,1,2,3 in decimal represented as <strong><em>i<\/em><\/strong>. The middle 4 bits of <strong><em>B<\/em><\/strong> corresponds to 0 to 15 in decimal (binary 0000 to 1111) represented as <strong><em>j<\/em><\/strong>. Check the corresponding S box for intersection of the row(ith in this case) with column(<strong><em>j<\/em><\/strong>-th in this case), the number is between 0 to 15 and can be depicted as a 4 bit block considered as <strong><em>S<\/em><\/strong><strong><em>1<\/em><\/strong><strong><em>(B)<\/em><\/strong> output .<\/p>\n<p>&nbsp;<\/p>\n<p style=\"text-align: justify\">For example block <strong><em>B<\/em><\/strong> = 011100 as input. &#8220;0&#8221; is the first bit and \u201c0\u201d is the last bit producing 00 for the row lookup. The in between four bits are &#8220;1110&#8221; equivalent to decimal 14.So lookup in column number 14. In row 0, column 14 the value stored is 0 in binary 0000. Hence <strong><em>S<\/em><\/strong><strong><em>1<\/em><\/strong>(011011) = 0000.<\/p>\n<p>&nbsp;<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"size-full wp-image-79 aligncenter\" src=\"http:\/\/itp4.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-43.png\" alt=\"\" width=\"851\" height=\"390\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-43.png 851w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-43-300x137.png 300w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-43-768x352.png 768w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-43-65x30.png 65w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-43-225x103.png 225w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-43-350x160.png 350w\" sizes=\"auto, (max-width: 851px) 100vw, 851px\" \/><\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"size-full wp-image-80 aligncenter\" src=\"http:\/\/itp4.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-44.png\" alt=\"\" width=\"850\" height=\"509\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-44.png 850w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-44-300x180.png 300w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-44-768x460.png 768w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-44-65x39.png 65w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-44-225x135.png 225w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-44-350x210.png 350w\" sizes=\"auto, (max-width: 850px) 100vw, 850px\" \/><\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"size-full wp-image-81 aligncenter\" src=\"http:\/\/itp4.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-45.png\" alt=\"\" width=\"890\" height=\"404\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-45.png 890w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-45-300x136.png 300w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-45-768x349.png 768w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-45-65x30.png 65w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-45-225x102.png 225w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-45-350x159.png 350w\" sizes=\"auto, (max-width: 890px) 100vw, 890px\" \/><\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"size-full wp-image-82 aligncenter\" src=\"http:\/\/itp4.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-46.png\" alt=\"\" width=\"816\" height=\"801\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-46.png 816w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-46-300x294.png 300w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-46-768x754.png 768w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-46-65x64.png 65w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-46-225x221.png 225w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-46-350x344.png 350w\" sizes=\"auto, (max-width: 816px) 100vw, 816px\" \/><\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"size-full wp-image-83 aligncenter\" src=\"http:\/\/itp4.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-47.png\" alt=\"\" width=\"883\" height=\"819\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-47.png 883w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-47-300x278.png 300w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-47-768x712.png 768w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-47-65x60.png 65w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-47-225x209.png 225w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-47-350x325.png 350w\" sizes=\"auto, (max-width: 883px) 100vw, 883px\" \/><\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"size-full wp-image-84 aligncenter\" src=\"http:\/\/itp4.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-48.png\" alt=\"\" width=\"818\" height=\"830\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-48.png 818w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-48-296x300.png 296w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-48-768x779.png 768w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-48-65x66.png 65w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-48-225x228.png 225w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-48-350x355.png 350w\" sizes=\"auto, (max-width: 818px) 100vw, 818px\" \/><\/p>\n<p>&nbsp;<\/p>\n<p>&nbsp;<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"size-full wp-image-85 aligncenter\" src=\"http:\/\/itp4.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-49.png\" alt=\"\" width=\"833\" height=\"368\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-49.png 833w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-49-300x133.png 300w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-49-768x339.png 768w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-49-65x29.png 65w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-49-225x99.png 225w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-49-350x155.png 350w\" sizes=\"auto, (max-width: 833px) 100vw, 833px\" \/><\/p>\n<ul>\n<li>\u00a8 The binary <em>output<\/em> 011000 010001 011110 111010 100001 100110 010100 100111. <em>results in <\/em>0101 1100 1000 0010 1011 0101 1001 0111 after passing through S-box.<\/li>\n<li>\u00a8 The last step is to permute output of S-box:<\/li>\n<\/ul>\n<p>The permutation is applied as per table <strong>P<\/strong>. Input is of 32-bit and output is of 32-bit.<\/p>\n<ul>\n<li>\u00a8 <strong>P<\/strong><\/li>\n<\/ul>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"size-full wp-image-86 aligncenter\" src=\"http:\/\/itp4.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-50.png\" alt=\"\" width=\"683\" height=\"520\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-50.png 683w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-50-300x228.png 300w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-50-65x49.png 65w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-50-225x171.png 225w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-50-350x266.png 350w\" sizes=\"auto, (max-width: 683px) 100vw, 683px\" \/><\/p>\n<ul>\n<li style=\"text-align: justify\">\u00a8 = 1100 1100 0000 0000 1100 1100 1111 1111 + 0010 0011 0100 1010 1010 1001 1011 1011 = 1110 1111 0100 1010 0110 0101 0100 0100<\/li>\n<li>\u00a8 For the second round, assign L2 = R1 and compute R2 =L1 + f(R1, K2), and repeat till round 16.<\/li>\n<li style=\"text-align: justify\">\u00a8 After round sixteen, L16 and R16 are generated. The order is reversed to generate the 64-bit block R16L16<\/li>\n<li>\u00a8 Finally <strong>IP<\/strong><strong>-1<\/strong> is applied for permutation<\/li>\n<\/ul>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"size-full wp-image-87 aligncenter\" src=\"http:\/\/itp4.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-51.png\" alt=\"\" width=\"614\" height=\"412\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-51.png 614w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-51-300x201.png 300w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-51-65x44.png 65w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-51-225x151.png 225w, https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-content\/uploads\/sites\/25\/2018\/07\/Untitled-51-350x235.png 350w\" sizes=\"auto, (max-width: 614px) 100vw, 614px\" \/><\/p>\n<p>Bit 40 takes first bit position, bit 8 takes second bit position, until bit 25 occupies last position.<\/p>\n<p>&nbsp;<\/p>\n<p>At the end of round 16:<\/p>\n<p>&nbsp;<\/p>\n<p>L16 = 0100 0011 0100 0010 0011 0010 0011 0100<\/p>\n<p>R16 = 0000 1010 0100 1100 1101 1001 1001 0101<\/p>\n<p>Order must be reversed and the final permutation must be applied:<\/p>\n<p>R16L16 = 00001010 01001100 11011001 10010101 01000011 01000010 00110010 00110100<\/p>\n<p>IP-1 = 10000101 11101000 00010011 01010100 00001111 00001010 10110100 00000101<\/p>\n<p>Convert to hexadecimal:<\/p>\n<p>85E813540F0AB405.<\/p>\n<p>Given M = 0123456789ABCDEF, encryption C = 85E813540F0AB405.<\/p>\n<p>&nbsp;<\/p>\n<p>Decryption:<\/p>\n<p>&nbsp;<\/p>\n<p>Decryption, inverse operation of encryption follows steps similar to encrytion, but keys are applied in the reverse way.<\/p>\n<p>&nbsp;<\/p>\n<p>The Strength of DES<\/p>\n<ul>\n<li>\u00a8 The use of 56-Bit keys.<\/li>\n<li>n 256 possible keys so brute force attack is impractical.<\/li>\n<li>\u00a8 The Nature of the DES algorithm.<\/li>\n<li>n Design criteria for S-boxes were not made public. No one has been successful in finding weakness in S-box.<\/li>\n<li>\u00a8 Timing attacks.<\/li>\n<li style=\"text-align: justify\">n Timing attack exploits that encryption and decryption algorithm takes slightly different amounts of time on different inputs.<\/li>\n<\/ul>\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<table>\n<tbody>\n<tr>\n<td><strong>you can view video on DES(Data Encryption Standard)<\/strong><\/td>\n<td><a href=\"https:\/\/youtu.be\/VdaQc0ERbw8\" 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>&nbsp;<\/p>\n","protected":false},"author":4,"menu_order":7,"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-68","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\/68","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\/68\/revisions"}],"predecessor-version":[{"id":433,"href":"https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-json\/pressbooks\/v2\/chapters\/68\/revisions\/433"}],"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\/68\/metadata\/"}],"wp:attachment":[{"href":"https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-json\/wp\/v2\/media?parent=68"}],"wp:term":[{"taxonomy":"chapter-type","embeddable":true,"href":"https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-json\/pressbooks\/v2\/chapter-type?post=68"},{"taxonomy":"contributor","embeddable":true,"href":"https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-json\/wp\/v2\/contributor?post=68"},{"taxonomy":"license","embeddable":true,"href":"https:\/\/ebooks.inflibnet.ac.in\/itp4\/wp-json\/wp\/v2\/license?post=68"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}