1 00:00:02,740 --> 00:00:10,460 And finally we'll take a look at an algorithm that does guarantee maximum security the Advanced Encryption 2 00:00:10,460 --> 00:00:20,800 Standard for it was entered into the competition with management it was bought by two Belgian cryptographers. 3 00:00:20,810 --> 00:00:28,150 The Advanced Encryption Standard is also offered to retail from the name of its creator. 4 00:00:28,170 --> 00:00:33,700 The difference between the two is that Greendale is more flexible some rain they'll support a block 5 00:00:33,700 --> 00:00:36,010 size and key size combinations. 6 00:00:36,070 --> 00:00:41,820 But if you get past the algorithm doesn't support these options. 7 00:00:41,820 --> 00:00:48,280 Now the winning cipher was selected in 2000 over 12 years ago. 8 00:00:53,090 --> 00:00:58,220 Ringtail over the Scifres Mars RC 6 serpent and Twofish 9 00:01:01,360 --> 00:01:07,610 RC 6 which we know about already was developed by Ron Rivest while Twofish like its predecessor Blowfish 10 00:01:07,670 --> 00:01:10,010 was created by Bruce Schneier. 11 00:01:10,170 --> 00:01:14,010 Another big name in cryptography. 12 00:01:14,040 --> 00:01:15,470 Now some details on it. 13 00:01:15,480 --> 00:01:16,170 Yes 14 00:01:19,980 --> 00:01:32,310 the cipher uses a killing of 128 to 256 bits it encrypts data blocks of fixed 128 bit length the number 15 00:01:32,310 --> 00:01:34,210 of rounds depends on the size of the key 16 00:01:36,750 --> 00:01:40,850 suggested key today should be 256 bits in length. 17 00:01:40,850 --> 00:01:47,740 Although the markets are. 18 00:01:47,990 --> 00:01:55,070 There will be 14 rounds in this configuration. 19 00:01:55,080 --> 00:01:59,490 It's interesting to note that the Advanced Encryption Standard does not use Feistel network 20 00:02:02,210 --> 00:02:07,110 the structure that it uses is hard to talk about without an animation or a graphical aid. 21 00:02:09,320 --> 00:02:15,570 For now remember that the round number is determined by the length of the key each round uses around 22 00:02:15,610 --> 00:02:20,600 key for each round for what. 23 00:02:20,840 --> 00:02:25,480 For They're divided into layers. 24 00:02:25,620 --> 00:02:28,710 The first is the nonlinear layer. 25 00:02:28,850 --> 00:02:36,150 The next is the mixing layer and the third is the key addition layer the non-linear layer it's a crucial 26 00:02:36,150 --> 00:02:36,980 stage. 27 00:02:38,090 --> 00:02:44,270 As you already know from the D.S. analysis substitutions are made in this layer to hide relationships 28 00:02:44,270 --> 00:02:46,970 between the plaintext and the ciphertext. 29 00:02:53,120 --> 00:02:55,970 So let's now take a closer look into yes. 30 00:02:57,900 --> 00:03:06,120 Before this a couple of words on terminology we'll use the term state a state is intermediate form in 31 00:03:06,120 --> 00:03:12,500 plaintext encryption or in other words it's the changing plain text values at each stage of the ABs 32 00:03:12,600 --> 00:03:14,090 encrypting process. 33 00:03:16,250 --> 00:03:22,670 States will be displayed as tables bytes of input messages will be in the intersection of columns and 34 00:03:22,670 --> 00:03:25,150 rows in the table. 35 00:03:25,160 --> 00:03:33,120 Likewise you can imagine the key to be displayed as a table. 36 00:03:33,260 --> 00:03:40,600 The first transformation the nonlinear transformation is the most important one. 37 00:03:40,670 --> 00:03:42,140 It's called the subsites the 38 00:03:44,870 --> 00:03:47,740 substitution boxes again used. 39 00:03:47,930 --> 00:03:52,800 And again we'll locate a value of the ciphertext bits based on the values of the plaintext bits. 40 00:03:54,890 --> 00:03:57,310 This relationship is completely non-linear. 41 00:04:02,260 --> 00:04:05,650 The second step involves shifting rows and moving columns. 42 00:04:07,360 --> 00:04:13,990 This is a simple operation that relies on shifting each row to the left mixing each column. 43 00:04:14,000 --> 00:04:18,300 The goal again is to obscure any relationships between the key and the ciphertext. 44 00:04:22,500 --> 00:04:30,990 In each round except the final round rows and column positions are transposed the final round involves 45 00:04:30,990 --> 00:04:35,480 only row shifting at the end of each round. 46 00:04:35,480 --> 00:04:41,420 The key is combined with the state the ADD round key operation is used for this purpose. 47 00:04:43,250 --> 00:04:47,320 The steps in total result in an efficient and very secure algorithm. 48 00:04:49,490 --> 00:04:52,190 The main appeal is the fact that it's a standard. 49 00:04:52,730 --> 00:04:59,790 If you're unsure which cipher to use for your solution I recommend the Advanced Encryption Standard. 50 00:04:59,910 --> 00:05:06,510 No one ever got fired for implementing an adopted standard even if a yes within five or 10 years proved 51 00:05:06,510 --> 00:05:12,510 to have some now unknown deficiencies which is unlikely because of one of the biggest strengths of public 52 00:05:12,510 --> 00:05:16,860 algorithms is that they're subjected to very intensive testing. 53 00:05:16,980 --> 00:05:23,710 You can always defend yourself saying that you have implemented the standard you can't be blamed for 54 00:05:23,710 --> 00:05:25,680 failing to predict it and have some faults.