高精度类实现 Diffie Hellman Algorithm

信息安全原理

作业2 第2题

高精度类写好了还不行

还要实现一下DH算法

那把表达式和DH算法写一个main()里吧

// name: main.cpp// author: amrzs// date: 2014/03/22#include <string>#include <iostream>#include "bigint.h"using namespace std;Bigint calc(Bigint a, Bigint b, char c){    Bigint result;    switch(c){        case '+':            result = a + b;            break;        case '-':            result = a - b;            break;        case '*':            result = a * b;            break;        case '/':            result = a / b;            break;        case '%':            result = a % b;            break;        default:            cout << "You input a wrong operator" << endl;            break;    }        return result;}int main(){    cout <<"If you want to calculate an expression then input \"EX 123456789 * 987654321\"" << endl        <<"if DH algorithm then input \"DH\" and something as follow" << endl;        string sFlag, s1, s2;    char ch;    while(1){ // don't like for(;;)                        cin >> sFlag;        if("EX" == sFlag){            cin >> s1 >> ch >> s2;            Bigint a(s1), b(s2);            Bigint result = calc(a, b, ch);            cout << "The result of expression is: ";            result.printNum();        }else if("DH" == sFlag){            cout << "Please input the shared message g and p" << endl;            cin >> s1 >> s2;            Bigint g(s1), p(s2);            cout << "Please input your secret key a" << endl;            cin >> s1;            Bigint a(s1), A;            A = g.getPow(a, p);            cout << "Your public key A is: ";            A.printNum();            cout << "You send g, p and A to another person" << endl;            cout << "He received your shared message p, g and public key A" << endl;            cout << "Please input his secret key b" << endl;            cin >> s1;            Bigint b(s1), B;            B = g.getPow(b, p);            cout << "His public key is: ";            B.printNum();            cout << "He sends the public key B to you" << endl;                        cout << "K = B^a mod p and you calculate the K is: " << endl;            Bigint K = B.getPow(a, p);            K.printNum();            cout << "K = A^b mod p and he calculates the K is: " << endl;            K = A.getPow(b, p);            K.printNum();        }else{            cout << "Your input is wrong, please try again!" << endl;        }        cout <<"If you want to calculate an expression then input EX 123456789 * 987654321" << endl            <<"if DH algorithm then input DH and something as follow" << endl;    }    return 0;}

按照维基百科上的小数据试了一下，没有问题

把DH写成函数了，再发一遍好了

// name: main.cpp// author: amrzs// date: 2014/03/22#include <string>#include <iostream>#include "bigint.h"using namespace std;Bigint calc(Bigint a, Bigint b, char c){    Bigint result;    switch(c){        case '+':            result = a + b;            break;        case '-':            result = a - b;            break;        case '*':            result = a * b;            break;        case '/':            result = a / b;            break;        case '%':            result = a % b;            break;        default:            cout << "You input a wrong operator" << endl;            break;    }        return result;}void DiffieHellman(){    string s1, s2;        cout << "Please input the shared message g and p" << endl;    cin >> s1 >> s2;    Bigint g(s1), p(s2);    cout << "Please input your secret key a" << endl;    cin >> s1;    Bigint a(s1), A;    A = g.getPow(a, p);    cout << "Your public key A is: " << endl;    A.printNum();    cout << "You send g, p and A to another person" << endl;    cout << "He received your shared message p, g and public key A" << endl;    cout << "Please input his secret key b" << endl;    cin >> s1;    Bigint b(s1), B;    B = g.getPow(b, p);    cout << "His public key is: " << endl;    B.printNum();    cout << "He sends the public key B to you" << endl;    cout << "K = B^a mod p and you calculate the K is: " << endl;    Bigint K = B.getPow(a, p);    K.printNum();    cout << "K = A^b mod p and he calculates the K is: " << endl;    K = A.getPow(b, p);    K.printNum();}int main(){    cout <<"If you want to calculate an expression then input \"EX 123456789 * 987654321\"" << endl        <<"if DH algorithm then input \"DH\" and something as follow" << endl;        string sFlag, s1, s2;    char ch;    while(1){ // don't like for(;;)                        cin >> sFlag;        if("EX" == sFlag){            cin >> s1 >> ch >> s2;            Bigint a(s1), b(s2);            Bigint result = calc(a, b, ch);            cout << "The result of expression is: ";            result.printNum();        }else if("DH" == sFlag){            DiffieHellman();        }else{            cout << "Your input is wrong, please try again!" << endl;        }        cout <<"If you want to calculate an expression then input EX 123456789 * 987654321" << endl            <<"if DH algorithm then input DH and something as follow" << endl;    }    return 0;}