信息安全古典密碼之凱撒密碼

《網(wǎng)絡(luò)攻擊與防御》實(shí)驗(yàn)報(bào)告計(jì)算機(jī)科學(xué)與技術(shù)學(xué)院計(jì)算機(jī)系網(wǎng)絡(luò)教研室制課程名稱：信息安全技術(shù)計(jì)算機(jī)科學(xué)與技術(shù)學(xué)院計(jì)算機(jī)系網(wǎng)絡(luò)教研室制課程名稱：信息安全技術(shù)實(shí)驗(yàn)名稱：古典密碼之凱撒密碼指導(dǎo)教師：學(xué)生姓名：組號(hào)：實(shí)驗(yàn)日期：實(shí)驗(yàn)地點(diǎn)：實(shí)驗(yàn)成績(jī)：實(shí)驗(yàn)報(bào)告書(shū)③已知c1=rxwvlghwkheleoh,wkhvhvlazrugvduhwkhprvwidprxvlqdoowkholwhudwxuhriwkhzruog.wkhbzhuhvsrnhqebkdpohwzkhqkhzdvwklqnlqjdorxg,dqgwkhbduhwkhprvwidprxvzrugvlqvkdnhvshduhehfdxvhkdpohwzdvvshdnlqjqrwrqobiruklpvhoiexwdovriruhyhubwklqnlqjpdqdqgzrpdq.wrehruqrwwreh,wrolyhruqrwwrolyh,wrolyhulfkobdqgdexqgdqwobdqghdjhuob,ruwrolyhgxoobdqgphdqobdqgvfdufhob.dsklorvrskhurqfhzdqwhgwrnqrzzkhwkhukhzdvdolyhruqrw,zklfklvdjrrgtxhvwlrqiruhyhubrqhwrsxwwrklpvhoirffdvlrqdoob.khdqvzhuhglwebvdblqj:"lwklqn,wkhuhiruhdp."，求p1。（高級(jí)解密）對(duì)給定較長(zhǎng)密文文件進(jìn)行解密測(cè)試，測(cè)試結(jié)果填入表。要求密文的內(nèi)容不少于1000個(gè)英文單詞，使用凱撒密碼加密，加密密碼保密。正確率=正確單詞數(shù)/單詞總數(shù)，智能程度：優(yōu)秀（解密結(jié)果正確與否不需要人工判斷）、一般。表四、實(shí)驗(yàn)過(guò)程與分析在允許輸入密碼條件下的實(shí)驗(yàn)結(jié)果。從file1中讀入明文，將密文存放在file2中在不允許輸入密碼條件下的實(shí)驗(yàn)結(jié)果在有單個(gè)字母的情況下，初級(jí)解密無(wú)單個(gè)字母下，中級(jí)解密，依次用1-25作為密鑰。高級(jí)解密初級(jí)解密：中級(jí)解密：高級(jí)解密：五、實(shí)驗(yàn)結(jié)果總結(jié)是一種最簡(jiǎn)單且最廣為人知的加密技術(shù)。它是一種替換加密的技術(shù)，\t"/item/%E6%81%BA%E6%92%92%E5%AF%86%E7%A0%81/_blank"明文中的所有字母都在\t"/item/%E6%81%BA%E6%92%92%E5%AF%86%E7%A0%81/_blank"字母表上向后（或向前）按照一個(gè)固定數(shù)目進(jìn)行偏移后被替換成\t"/item/%E6%81%BA%E6%92%92%E5%AF%86%E7%A0%81/_blank"密文。例如，當(dāng)偏移量是3的時(shí)候，所有的字母A將被替換成D，B變成E，以此類推。使用時(shí)，加密者查找明文字母表中需要加密的消息中的每一個(gè)字母所在位置，并且寫(xiě)下密文字母表中對(duì)應(yīng)的字母。需要解密的人則根據(jù)事先已知的密鑰反過(guò)來(lái)操作，得到原來(lái)的明文。源代碼：#include<fstream>#include<iostream>#include<string>#include<cmath>#include<Windows.h>#defineN1000#defineTARGET0.065379#defineLIST_LEN26usingnamespacestd;constdoublep[LIST_LEN]={0.082,0.015,0.028,0.042,0.127,0.022,0.02,0.061,0.07,0.001,0.008,0.04,0.024,0.067,0.075,0.019,0.001,0.06,0.063,0.09,0.028,0.01,0.024,0.02,0.001,0.001};stringdict[7]={"we","be","to","am","you","are","the"};voidfile_print(char*filename){ifstreaminfile;charch;inti=0;infile.open(filename,ios::in);if(!infile){cout<<"openerror!"<<endl;exit(1);}while(infile.get(ch)){cout<<ch;}cout<<endl;infile.close();}intnumber(char*filename){ifstreaminfile;charch;inti=0;infile.open(filename,ios::in);if(!infile){cout<<"openerror!"<<endl;exit(1);}while(infile.get(ch)){i++;}infile.close();returni;}voidEncrypt(){ifstreaminfile;ofstreamoutfile;charch,*code;unsignedcharstr[N];code=newchar(2);cout<<"明文為："<<endl;file_print("file1.txt");intn=number("file1.txt");infile.open("file1.txt",ios::in);if(!infile){cout<<"openerror!"<<endl;exit(1);}cout<<"請(qǐng)輸入一位英文字符密碼："<<endl;cin>>code;code[1]='\0';//cout<<code[1];if(code[1]!='\0')cout<<"輸入錯(cuò)誤，請(qǐng)輸入一位英文字符："<<endl;if(code[0]>=65&&code[0]<=90){code[0]+=32;}for(inti=0;i<n;i++){infile>>str[i];}outfile.open("file2.txt");if(!outfile){cout<<"openerror!"<<endl;exit(1);}intkey=code[0]-97;cout<<"密鑰為："<<key<<endl;for(i=0;str[i]!=0;i++){if(str[i]>=65&&str[i]<=90)str[i]+=32;if(str[i]<97||str[i]>122)continue;str[i]+=key;if(str[i]>122){str[i]-=26;}outfile.put(str[i]);}infile.close();outfile.close();cout<<"密文為："<<endl;file_print("file2.txt");}voidprimary(charc){DWORDstart_time=GetTickCount();ifstreaminfile;charch;unsignedcharstr[N];infile.open("file3.txt",ios::in);if(!infile){cout<<"openerror!"<<endl;exit(1);}for(inti=0;infile.get(ch);i++){str[i]=ch;//cout<<str[i];}intkey=abs(c-'a');//cout<<key;cout<<"密文為："<<endl;file_print("file3.txt");intn=number("file3.txt");//cout<<n;cout<<"明文為："<<endl;for(i=0;i<n;i++){if(str[i]=='') {str[i]=32; cout<<str[i]; }if(str[i]<97||str[i]>122) cout<<str[i];else{ str[i]-=key; if(str[i]<97)str[i]+=26; cout<<str[i]; }}cout<<endl;infile.close();DWORDend_time=GetTickCount();cout<<"解密時(shí)間為："<<end_time-start_time<<"ms!"<<endl;}voidMediate_senior(unsignedcharstr[],intn){intkey=1;intsimilar=0;for(inti=0;i<n;i++){if(str[i]=='') {str[i]=32; cout<<str[i]; }if(str[i]<97||str[i]>122) cout<<str[i];else{ str[i]-=key; if(str[i]<97)str[i]+=26; cout<<str[i]; }}}voidintermediate(){DWORDstart_time=GetTickCount();ifstreaminfile;charch;unsignedcharstr[N];infile.open("file3.txt",ios::in);if(!infile){cout<<"openerror!"<<endl;exit(1);}cout<<"密文為："<<endl;for(inti=0;infile.get(ch);i++) {str[i]=ch; cout<<ch; }cout<<endl;for(intn=1;n<=25;n++){cout<<"k="<<n<<'';Mediate_senior(str,number("file3.txt"));printf("\n");}DWORDend_time=GetTickCount();cout<<"解密時(shí)間為："<<end_time-start_time<<"ms!"<<endl;}/*統(tǒng)計(jì)filename中字母出現(xiàn)頻率，存放在數(shù)組q中*/voidcount(constcharfilename[],doubleq[LIST_LEN]){inti,len=0;/*len為字母總個(gè)數(shù)約等于密文長(zhǎng)度*/FILE*fin=fopen(filename,"r");charch;for(i=0;i<LIST_LEN;i++)q[i]=0;while((ch=fgetc(fin))!=EOF){if(isalpha(ch)){len++;ch=tolower(ch);q[ch-'a']+=1;}}fclose(fin);for(i=0;i<LIST_LEN;i++)q[i]/=len;}/*破解密鑰key，并且將其中數(shù)組q存放密文字母出現(xiàn)頻率*/intanalysis(constcharfilename[],doubleq[LIST_LEN]){inti,j,key=0;doubleeps=1;/*eps存儲(chǔ)與TARGET最小差值*/count(filename,q);for(j=0;j<LIST_LEN;j++){/*變量j窮舉密鑰*/doublesum=0,tem;for(i=0;i<LIST_LEN;i++){/*求sum{p[i]*q[i+j]}之和*/intt=(i+j)%26;sum+=p[i]*q[t];}tem=fabs(sum-TARGET);if(tem<eps){eps=tem;key=j;}}returnkey：}voidsenior(){ifstreaminfile;charch;unsignedcharstr[N];infile.open("file4.txt",ios::in);if(!infile){cout<<"openerror!"<<endl;exit(1);}for(inti=0;infile.get(ch);i++){str[i]=ch;//cout<<str[i];}doubleq[LIST_LEN];intkey=analysis("file4.txt",q);//cout<<key;file_print("file4.txt");intn=number("file4.txt");//cout<<n;for(i=0;i<n;i++){if(str[i]=='') {str[i]=32; cout<<str[i]; }if(str[i]<97||str[i]>122) cout<<str[i];else{ str[i]-=key; if(str[i]<97)str[i]+=26; cout<<str[i]; }}cout<<endl;infile.clo