1 00:00:00,810 --> 00:00:05,900 Hello and welcome to a new section in this new session. 2 00:00:05,910 --> 00:00:14,770 We are going to learn how to write external key things as we have seen in the previous lessons. 3 00:00:14,860 --> 00:00:17,070 There are two types of key events. 4 00:00:17,110 --> 00:00:27,040 The first one is called self keychain and this is very partially software to display the hero key and 5 00:00:27,040 --> 00:00:34,550 we have completed that one and the second way is to write an external key again. 6 00:00:34,630 --> 00:00:40,920 This is the way we will write separate program to implement the algorithm that creates this hero key 7 00:00:42,430 --> 00:00:47,250 and extend the key yens can be either come online based on this. 8 00:00:47,980 --> 00:00:52,730 In this session I'm going to show you how to write an external keychain. 9 00:00:53,710 --> 00:00:59,280 There is a workflow that you can use when creating an extended keychain. 10 00:00:59,380 --> 00:01:09,690 Step one bash this target software to create a self key And first why do you need to patch this over 11 00:01:10,180 --> 00:01:12,260 to create yourself first. 12 00:01:12,730 --> 00:01:21,910 Because that is the easier way to create Keegan and you need to have a key again in order to study the 13 00:01:21,910 --> 00:01:32,200 output that way based on the observation of the output of this key from this again you will get a better 14 00:01:32,290 --> 00:01:39,280 understanding of how this hierarchy is being generated. 15 00:01:39,310 --> 00:01:48,880 You can also use this occasion to test your estimate key again when doing the coding 16 00:01:51,680 --> 00:01:56,570 second study the disassembly and you'll get minimal instructions. 17 00:01:56,660 --> 00:02:06,320 This January this year key to this assembly here is referring to the ICC for debugging debugger which 18 00:02:06,320 --> 00:02:11,680 is used to DBA the software that you are targeting. 19 00:02:11,720 --> 00:02:23,630 So the step here involves locating the instructions that are actually generating these Hiroki and you 20 00:02:23,630 --> 00:02:32,000 will find that there are many lines of code sometimes but you need to narrow it down to only those few 21 00:02:32,000 --> 00:02:39,290 lines which are actually generating the important part of the zero key. 22 00:02:39,290 --> 00:02:41,330 So that is what we mean by minimal 23 00:02:45,550 --> 00:02:53,190 Number Three copy those instructions out using copy to plug in. 24 00:02:53,740 --> 00:03:03,040 So a copy to us and plug in is a plug in that you need to install in the SCC for the energy in order 25 00:03:03,040 --> 00:03:10,870 to allow you to select regions of the disassemble code to copy to a separate file 26 00:03:13,990 --> 00:03:22,780 set for paste a copy instructions to the key template key chain template has been discussed in the previous 27 00:03:22,780 --> 00:03:34,390 session and this template is a simple assembly code which you can use and modify in order to become 28 00:03:35,230 --> 00:03:45,660 an hysteric again for the target software that you are trying to create a key gain for Step 5 modify 29 00:03:45,660 --> 00:03:48,380 the instructions of the key template. 30 00:03:48,780 --> 00:03:58,470 You need to modify the variable names he addresses and a few other things as well. 31 00:03:58,590 --> 00:04:05,580 Step six run and compare the zero key media circuit against Syria key. 32 00:04:05,610 --> 00:04:09,080 So this is where the circle jerk becomes useful. 33 00:04:09,240 --> 00:04:17,500 So after you modify your key Jen template if to paste it could you into the test it. 34 00:04:18,150 --> 00:04:22,830 And how would you know then this Iraqi unity is correct. 35 00:04:22,830 --> 00:04:32,280 You can compare it against the circle against Hiroki if your s to you can produce the same 0 key as 36 00:04:32,280 --> 00:04:32,740 yourself. 37 00:04:32,760 --> 00:04:44,670 Again it means you have correctly retain your extended key in Step Seven repeat from step two or step 38 00:04:44,670 --> 00:04:49,560 five until this key matches in this circle. 39 00:04:50,190 --> 00:04:57,750 So this is a ITER Retief steps and you need to repeat a few times many times maybe until you get it 40 00:04:57,750 --> 00:05:06,330 right your first trial most probably you get a lot of errors and maybe even wrong key and so you need 41 00:05:06,330 --> 00:05:07,440 to repeat. 42 00:05:07,710 --> 00:05:15,210 Sometimes you need to repeat from Step two maybe you copy the wrong part of the code and so you have 43 00:05:15,210 --> 00:05:24,630 to go back to step two and analyze again and copy on different parts or sometimes your unit and go back 44 00:05:24,630 --> 00:05:26,020 to step five. 45 00:05:26,140 --> 00:05:33,360 Maybe your modification that you did was not optimal or maybe even wrong. 46 00:05:34,410 --> 00:05:44,870 So you may need to repeat these steps many times until your standard kitchen produces a series key that 47 00:05:44,910 --> 00:05:47,950 matches units safety against Syria key. 48 00:05:48,030 --> 00:05:56,360 So once you've done that it means you successfully create an external kitchen so that's all for this 49 00:05:56,360 --> 00:06:05,500 a workflow explanation in this lesson is that if our protocol on how to do the standard kitchen. 50 00:06:05,600 --> 00:06:07,400 Thank you very much for watching. 51 00:06:07,430 --> 00:06:08,020 See you then.