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183 lines
4.0 KiB
C++
183 lines
4.0 KiB
C++
/*This C++ program encodes any message using RSA Algorithm. Input is case sensitive and works only for all characters. RSA is one of the first practicable public-key cryptosystems and is widely used for secure data transmission. In such a cryptosystem, the encryption key is public and differs from the decryption key which is kept secret. In RSA, this asymmetry is based on the practical difficulty of factoring the product of two large prime numbers, the factoring problem. RSA stands for Ron Rivest, Adi Shamir and Leonard Adleman.*/
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/*
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* C++ Program to Implement the RSA Algorithm
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*/
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#include<iostream>
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#include<math.h>
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#include<string.h>
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#include<stdlib.h>
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using namespace std;
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long int p, q, n, t, flag, e[100], d[100], temp[100], j, m[100], en[100], i;
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char msg[100];
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int prime(long int);
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void ce();
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long int cd(long int);
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void encrypt();
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void decrypt();
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int prime(long int pr)
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{
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int i;
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j = sqrt(pr);
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for (i = 2; i <= j; i++)
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{
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if (pr % i == 0)
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return 0;
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}
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return 1;
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}
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int main()
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{
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cout << "\nENTER FIRST PRIME NUMBER\n";
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cin >> p;
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flag = prime(p);
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if (flag == 0)
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{
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cout << "\nWRONG INPUT\n";
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exit(1);
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}
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cout << "\nENTER ANOTHER PRIME NUMBER\n";
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cin >> q;
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flag = prime(q);
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if (flag == 0 || p == q)
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{
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cout << "\nWRONG INPUT\n";
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exit(1);
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}
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cout << "\nENTER MESSAGE\n";
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fflush(stdin);
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cin >> msg;
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for (i = 0; msg[i] != NULL; i++)
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m[i] = msg[i];
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n = p * q;
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t = (p - 1) * (q - 1);
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ce();
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cout << "\nPOSSIBLE VALUES OF e AND d ARE\n";
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for (i = 0; i < j - 1; i++)
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cout << e[i] << "\t" << d[i] << "\n";
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encrypt();
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decrypt();
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return 0;
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}
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void ce()
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{
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int k;
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k = 0;
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for (i = 2; i < t; i++)
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{
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if (t % i == 0)
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continue;
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flag = prime(i);
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if (flag == 1 && i != p && i != q)
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{
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e[k] = i;
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flag = cd(e[k]);
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if (flag > 0)
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{
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d[k] = flag;
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k++;
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}
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if (k == 99)
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break;
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}
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}
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}
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long int cd(long int x)
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{
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long int k = 1;
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while (1)
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{
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k = k + t;
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if (k % x == 0)
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return (k / x);
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}
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}
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void encrypt()
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{
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long int pt, ct, key = e[0], k, len;
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i = 0;
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len = strlen(msg);
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while (i != len)
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{
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pt = m[i];
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pt = pt - 96;
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k = 1;
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for (j = 0; j < key; j++)
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{
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k = k * pt;
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k = k % n;
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}
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temp[i] = k;
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ct = k + 96;
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en[i] = ct;
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i++;
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}
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en[i] = -1;
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cout << "\nTHE ENCRYPTED MESSAGE IS\n";
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for (i = 0; en[i] != -1; i++)
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printf("%c", en[i]);
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}
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void decrypt()
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{
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long int pt, ct, key = d[0], k;
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i = 0;
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while (en[i] != -1)
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{
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ct = temp[i];
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k = 1;
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for (j = 0; j < key; j++)
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{
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k = k * ct;
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k = k % n;
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}
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pt = k + 96;
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m[i] = pt;
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i++;
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}
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m[i] = -1;
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cout << "\nTHE DECRYPTED MESSAGE IS\n";
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for (i = 0; m[i] != -1; i++)
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printf("%c", m[i]);
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}
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/*
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ENTER FIRST PRIME NUMBER
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47
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ENTER ANOTHER PRIME NUMBER
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53
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ENTER MESSAGE
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Dharmendra
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POSSIBLE VALUES OF e AND d ARE
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3 1595
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5 957
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7 1367
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11 435
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17 985
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19 1259
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29 165
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31 463
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37 1293
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41 2217
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43 1947
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59 1419
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61 549
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67 2035
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71 1415
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73 1409
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79 1847
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83 2075
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89 2177
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97 1233
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101 1421
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103 2183
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THE ENCRYPTED MESSAGE IS
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x`a???]??a
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THE DECRYPTED MESSAGE IS
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Dharmendra
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