blog/assets/js/d05e838c.a0757fee.js

"use strict";(self.webpackChunkfi=self.webpackChunkfi||[]).push([[6544],{3004:(e,n,r)=>{r.r(n),r.d(n,{assets:()=>d,contentTitle:()=>c,default:()=>a,frontMatter:()=>i,metadata:()=>o,toc:()=>l});var s=r(5893),t=r(1151);const i={id:"seminar-05-06",title:"5th and 6th seminar",description:"200IQ encryption.\n"},c=void 0,o={id:"bonuses/seminar-05-06",title:"5th and 6th seminar",description:"200IQ encryption.\n",source:"@site/c/bonuses/05-06.md",sourceDirName:"bonuses",slug:"/bonuses/seminar-05-06",permalink:"/c/bonuses/seminar-05-06",draft:!1,unlisted:!1,editUrl:"https://github.com/mfocko/blog/tree/main/c/bonuses/05-06.md",tags:[],version:"current",lastUpdatedAt:1700841229,formattedLastUpdatedAt:"Nov 24, 2023",frontMatter:{id:"seminar-05-06",title:"5th and 6th seminar",description:"200IQ encryption.\n"},sidebar:"autogeneratedBar",previous:{title:"4th seminar",permalink:"/c/bonuses/seminar-04"},next:{title:"8th seminar",permalink:"/c/bonuses/seminar-08"}},d={},l=[{value:"Introduction",id:"introduction",level:2},{value:"Task no. 1: Reverse (0.5 K\u20a1)",id:"task-no-1-reverse-05-k",level:3},{value:"Task no. 2: Vigen\xe8re (0.5 K\u20a1)",id:"task-no-2-vigen\xe8re-05-k",level:3},{value:"Bonus part (0.5 K\u20a1)",id:"bonus-part-05-k",level:4},{value:"Task no. 3: Bit madness (0.5 K\u20a1)",id:"task-no-3-bit-madness-05-k",level:3},{value:"Task no. 4: All combined to BMP (0.5 K\u20a1)",id:"task-no-4-all-combined-to-bmp-05-k",level:3},{value:"Submitting",id:"submitting",level:2}];function h(e){const n={a:"a",code:"code",h2:"h2",h3:"h3",h4:"h4",hr:"hr",li:"li",ol:"ol",p:"p",pre:"pre",ul:"ul",...(0,t.a)(),...e.components};return(0,s.jsxs)(s.Fragment,{children:[(0,s.jsx)(n.p,{children:"For this bonus you can get at maximum 2.5 K\u20a1."}),"\n",(0,s.jsx)(n.p,{children:(0,s.jsx)(n.a,{href:"pathname:///files/c/bonuses/05-06.tar.gz",children:"Source"})}),"\n",(0,s.jsx)(n.h2,{id:"introduction",children:"Introduction"}),"\n",(0,s.jsx)(n.p,{children:"In this bonus you will implement few functions that will be used together for\nimplementing a very special cipher."}),"\n",(0,s.jsx)(n.h3,{id:"task-no-1-reverse-05-k",children:"Task no. 1: Reverse (0.5 K\u20a1)"}),"\n",(0,s.jsxs)(n.p,{children:["Write a function ",(0,s.jsx)(n.code,{children:"char* reverse(const char* text)"})," that returns copy of the input\nstring in reversed order (also uppercase)."]}),"\n",(0,s.jsxs)(n.p,{children:["In case you are given ",(0,s.jsx)(n.code,{children:"NULL"}),", return ",(0,s.jsx)(n.code,{children:"NULL"}),"."]}),"\n",(0,s.jsx)(n.p,{children:"Example (more in tests):"}),"\n",(0,s.jsx)(n.pre,{children:(0,s.jsx)(n.code,{className:"language-c",children:'char* reversed = reverse("Hello world!");\n\nprintf("%s\\n", reversed);\n// "!DLROW OLLEH"\n\nif (reversed != NULL) {\n    free(reversed);\n}\n'})}),"\n",(0,s.jsx)(n.h3,{id:"task-no-2-vigen\xe8re-05-k",children:"Task no. 2: Vigen\xe8re (0.5 K\u20a1)"}),"\n",(0,s.jsx)(n.p,{children:"Vigen\xe8re cipher is similar to the Caesar cipher, but you also have a key that is\nused for encrypting (or decrypting)."}),"\n",(0,s.jsx)(n.p,{children:"Your task is to write two functions:"}),"\n",(0,s.jsxs)(n.ul,{children:["\n",(0,s.jsxs)(n.li,{children:[(0,s.jsx)(n.code,{children:"char* vigenere_encrypt(const char* key, const char* text)"})," for encrypting"]}),"\n",(0,s.jsxs)(n.li,{children:[(0,s.jsx)(n.code,{children:"char* vigenere_decrypt(const char* key, const char* text)"})," for decrypting"]}),"\n"]}),"\n",(0,s.jsx)(n.p,{children:"In both of those you should return uppercase characters."}),"\n",(0,s.jsx)(n.p,{children:"Meaning of the parameters you are given:"}),"\n",(0,s.jsxs)(n.ul,{children:["\n",(0,s.jsxs)(n.li,{children:[(0,s.jsx)(n.code,{children:"key"})," - String that represents key that is used for *crypting. It consists of\none word and can have only characters of the alphabet. Does not matter if they\nare uppercase or lowercase."]}),"\n",(0,s.jsxs)(n.li,{children:[(0,s.jsx)(n.code,{children:"text"})," - String that is to be *crypted."]}),"\n"]}),"\n",(0,s.jsxs)(n.p,{children:["Function returns address of the encrypted (or decrypted) string. Or ",(0,s.jsx)(n.code,{children:"NULL"})," in case\nerror occurs."]}),"\n",(0,s.jsx)(n.p,{children:"Example:"}),"\n",(0,s.jsx)(n.pre,{children:(0,s.jsx)(n.code,{className:"language-c",children:'char *encrypted = vigenere_encrypt("CoMPuTeR", "Hello world!");\n\nprintf("%s\\n", encrypted);\n// "JSXAI PSINR!"\n\nif (encrypted != NULL) {\n    free(encrypted)\n}\n'})}),"\n",(0,s.jsx)(n.h4,{id:"bonus-part-05-k",children:"Bonus part (0.5 K\u20a1)"}),"\n",(0,s.jsx)(n.p,{children:"If you can utilize helper function that would do both encrypting and decrypting,\nyou can gain 0.5 K\u20a1."}),"\n",(0,s.jsxs)(n.p,{children:["Usage of ",(0,s.jsx)(n.code,{children:"true"}),"/",(0,s.jsx)(n.code,{children:"false"})," to decide path in code is prohibited. It leads to merging\nof both functions into one. Point of this part is to discover a way to do this\ngenerically in such way that there are no separate paths for one or the other. One\nfunction with no branching for both of them, parametrization is your friend :)"]}),"\n",(0,s.jsx)(n.h3,{id:"task-no-3-bit-madness-05-k",children:"Task no. 3: Bit madness (0.5 K\u20a1)"}),"\n",(0,s.jsx)(n.p,{children:"This is a state of the art crypto. Please do not share :)"}),"\n",(0,s.jsx)(n.p,{children:"For encrypting:"}),"\n",(0,s.jsxs)(n.ol,{children:["\n",(0,s.jsx)(n.li,{children:"Split the character that is to be encrypted in halves (4 and 4 bits each)."}),"\n",(0,s.jsx)(n.li,{children:"Bits in 1st half are to be split into pairs. Swap bits in those pairs."}),"\n",(0,s.jsxs)(n.li,{children:["Then use the 4 bits that you created in the 2nd step for ",(0,s.jsx)(n.code,{children:"XOR"})," with the other\n4 bits."]}),"\n"]}),"\n",(0,s.jsxs)(n.p,{children:["This simple and ingenious principle will be illustrated on the following example.\nString we want to encrypt is ",(0,s.jsx)(n.code,{children:"Hello world!"}),". We need to encrypt each letter separately,\nso we will demonstrate on letter ",(0,s.jsx)(n.code,{children:"H"}),":"]}),"\n",(0,s.jsxs)(n.ol,{children:["\n",(0,s.jsxs)(n.li,{children:["\n",(0,s.jsxs)(n.p,{children:["Letter ",(0,s.jsx)(n.code,{children:"H"})," is represented in ASCII as ",(0,s.jsx)(n.code,{children:"72"}),"."]}),"\n",(0,s.jsxs)(n.p,{children:[(0,s.jsx)(n.code,{children:"72"})," represented in binary is: ",(0,s.jsx)(n.code,{children:"01001000"}),". So first 4 bits are: ",(0,s.jsx)(n.code,{children:"0100"})," and last\n4 bits are ",(0,s.jsx)(n.code,{children:"1000"}),"."]}),"\n"]}),"\n",(0,s.jsxs)(n.li,{children:["\n",(0,s.jsxs)(n.p,{children:["First half of bits (",(0,s.jsx)(n.code,{children:"0100"}),") consists of 2 pairs (",(0,s.jsx)(n.code,{children:"01"})," and ",(0,s.jsx)(n.code,{children:"00"}),") which we swap\n(",(0,s.jsx)(n.code,{children:"01 ~> 10"})," and ",(0,s.jsx)(n.code,{children:"00 ~> 00"}),"). That way we get ",(0,s.jsx)(n.code,{children:"1000"}),"."]}),"\n"]}),"\n",(0,s.jsxs)(n.li,{children:["\n",(0,s.jsx)(n.p,{children:"That half is used for xor with the other 4 bits:"}),"\n",(0,s.jsx)(n.pre,{children:(0,s.jsx)(n.code,{children:"    1000  // second half\nXOR 1000  // first half after 2nd step\n--------\n    0000\n"})}),"\n"]}),"\n",(0,s.jsxs)(n.li,{children:["\n",(0,s.jsxs)(n.p,{children:["Now we combine both halves (first one is ",(0,s.jsx)(n.code,{children:"1000"}),", which we got from the 2nd step\nand second one is ",(0,s.jsx)(n.code,{children:"0000"}),", which we got from the 3rd step) and get ",(0,s.jsx)(n.code,{children:"10000000"}),",\nwhich is encrypted character ",(0,s.jsx)(n.code,{children:"H"})," using this method."]}),"\n"]}),"\n"]}),"\n",(0,s.jsx)(n.p,{children:"In case of decryption, reverse those steps."}),"\n",(0,s.jsx)(n.p,{children:"Your task is to implement functions:"}),"\n",(0,s.jsxs)(n.ul,{children:["\n",(0,s.jsx)(n.li,{children:(0,s.jsx)(n.code,{children:"unsigned char* bit_encrypt(const char* text)"})}),"\n",(0,s.jsx)(n.li,{children:(0,s.jsx)(n.code,{children:"char* bit_decrypt(const unsigned char* text)"})}),"\n"]}),"\n",(0,s.jsx)(n.p,{children:"Example:"}),"\n",(0,s.jsx)(n.pre,{children:(0,s.jsx)(n.code,{className:"language-c",children:'unsigned char* encrypted = bit_encrypt("Hello world!");\n\nfor (int i = 0; i < 12;i++) {\n    printf("%x ", encrypted[i]);\n    //80 9c 95 95 96 11 bc 96 b9 95 9d 10\n}\n\nif (encrypted != NULL) {\n    free(encrypted);\n}\n'})}),"\n",(0,s.jsx)(n.h3,{id:"task-no-4-all-combined-to-bmp-05-k",children:"Task no. 4: All combined to BMP (0.5 K\u20a1)"}),"\n",(0,s.jsx)(n.p,{children:"Authors of the BMP cipher are non-disclosed :)"}),"\n",(0,s.jsx)(n.p,{children:"Create pair of functions:"}),"\n",(0,s.jsxs)(n.ul,{children:["\n",(0,s.jsx)(n.li,{children:(0,s.jsx)(n.code,{children:"unsigned char* bmp_encrypt(const char* key, const char* text)"})}),"\n",(0,s.jsx)(n.li,{children:(0,s.jsx)(n.code,{children:"char* bmp_decrypt(const char* key, const unsigned char* text)"})}),"\n"]}),"\n",(0,s.jsx)(n.p,{children:"BMP cipher consists of following steps for encrypting:"}),"\n",(0,s.jsxs)(n.ol,{children:["\n",(0,s.jsx)(n.li,{children:"Reverse the input string"}),"\n",(0,s.jsx)(n.li,{children:"Use Vigenere on the string you got from step #1"}),"\n",(0,s.jsx)(n.li,{children:"Use bit madness on the string you got from step #2"}),"\n"]}),"\n",(0,s.jsx)(n.p,{children:"For decrypting, reverse the steps."}),"\n",(0,s.jsx)(n.h2,{id:"submitting",children:"Submitting"}),"\n",(0,s.jsx)(n.p,{children:"In case you have any questions, feel free to reach out to me."}),"\n",(0,s.jsx)(n.hr,{})]})}function a(e={}){const{wrapper:n}={...(0,t.a)(),...e.components};return n?(0,s.jsx)(n,{...e,children:(0,s.jsx)(h,{...e})}):h(e)}},1151:(e,n,r)=>{r.d(n,{Z:()=>o,a:()=>c});var s=r(7294);const t={},i=s.createContext(t);function c(e){const n=s.useContext(i);return s.useMemo((function(){return"function"==typeof e?e(n):{...n,...e}}),[n,e])}function o(e){let n;return n=e.disableParentContext?"function"==typeof e.components?e.components(t):e.components||t:c(e.components),s.createElement(i.Provider,{value:n},e.children)}}}]);