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Title RSA Algorithm (Mini Project)
Author Lekshmi.K
Author Email reachachme [at] yahoo.com
Description It encrypts not only the numbers, also the text message you will give.
Category C++ » Algorithms
Hits 361118
Code Select and Copy the Code
Code : //Header File--RSA Application //Miller & Rabin Algorithm--Test for Primality //PseudoRandom Number Generator Algorithm //Relatively Prime--Euclid's Algorithm #include<iostream.h> #include<stdio.h> #include<stdlib.h> #include<string.h> #include<conio.h> #include<math.h> #include<process.h> class RSA { public: int pr1,pr2,x1,n,n1; int e,d,pt; int a[20],b[10]; int len; //binary array length RSA(); //Miller & Rabin Algorithm--Test for Primality void testprimality(); //PseudoRandom Number Generator Algorithm void pseudo1(); int pseudo2(); //Relatively Prime--Euclid's Algorithm //GCD of two numbers-their common factor is '1' void relprime(); int gcd(int c,int d); //Key Generation int keygenerate1(int ptext);//for Encryption int keygenerate2(int ctext);//for Decryption void decitobin(int x); //Encryption int encrypt(int num); //Decryption int decrypt(int ctext); }; //Interface File--RSA Application //Miller & Rabin Algorithm--Test for Primality //PseudoRandom Number Generator Algorithm //Relatively Prime--Euclid's Algorithm #include"rh1.h" RSA::RSA() { x1=1; pr1=0; pr2=0; } //Miller & Rabin Algorithm--Test for Primality void RSA::testprimality() { int a,j,p1,q,x; int t1,t2; int k,flag,ch; ch=1; flag=0; k=0; //(n-1)=pow(2,k)*q //divide (n-1) by 2 until result is odd number while(ch) { x=(n-1)/(int)(pow(2,k)); if(fmod(x,2)==1) { ch=0; break; } k++; } q=(int)((n-1)/(pow(2,k))); //to pick an integer randomly which //should be less than 'n'; //That's why calling pseudo2() a=pseudo2(); if(a>1 && a<(n-1)) { t1=(int)(pow(a,q)); if((t1%n)==1) flag=1; else { for(j=0;j<=(k-1);j++) { p1=((int)(pow(2,j)))*q; t2=(int)pow(a,p1); if((t2%n)==(n-1)) flag=1; } } } if(flag==1) if(pr1==0) pr1=n; else if(pr1!=0 && pr2==0) pr2=n; } //PseudoRandom Number Generator Algorithm void RSA::pseudo1() { //to select 'n' pseudorandomly and pass to testprimality(); //'n' is to be proved either prime or not prime int a,c,y; unsigned int m; y=0; a=(int)pow(7,5); //(7,2),*(7,4),(7,5) //(int)pow(7,5) used in IBM 360 //m should be assigned a "prime" no. //up to pow(2,31) should be used. //(2,5)-1;(2,7)-1;(2,13)-1; //(2,17)-1;(2,19)-1;(2,31)-1 are primes m=((int)pow(2,7))-1; //(2,7) n=1;c=0; for(int i=0;i<50;i++) { n=((a*n)+c)%m; testprimality(); //n will be computed in textprimality() } // cout<<" pr1 = "<<pr1; // cout<<" pr2 = "<<pr2; } int RSA::pseudo2() { //to pick an integer randomly which //should be less than 'n' int a,ret; unsigned int m; a=(int)pow(7,4); //(7,3),*(7,4) for a's (7,5)in pseudo1 m=(int)pow(2,5)-1; //(2,5) ret=(a*x1)%m; x1=ret; return ret; } //Relatively Prime--Euclid's Algorithm //GCD of two numbers-their common factor is '1' void RSA::relprime() { //Finding 'e' & 'd' value int fin,ret,ret1,ret2,ch,ex,dx; ch=1;ex=2;dx=1; n1=pr1*pr2; fin=(pr1-1)*(pr2-1); //Finding 'e' alone x1=1; //for pseudo2 while(ch) { ex=pseudo2(); if(ex>1 && ex<fin) { ret1=gcd(ex,fin); ret2=gcd(fin,(ex%fin)); if(ret1==1 && ret2==1) { e=ex; ch=0; break; } } } // cout<<" Relative Prime : e value: "<<e; //Finding 'd' alone //de=(1 mod fin) where fin=(pr1-1)*(pr2-1); ch=1; while(ch) { ret=(e*dx)%fin; if(ret==1) { d=dx; ch=0; break; } dx=dx+1; } // cout<<" d value : "<<d; } int RSA::gcd(int c,int d) { int r; r=d%c; while(r!=0) { d=c; c=r; r=d%c; } return c; } int RSA::keygenerate1(int ptext) { //Encryption int i,c; int entext; c=0;entext=1; decitobin(e); //public key with 'e' //b[]->array contains binary value of 'e' for(i=len;i>=0;i--) { c=2*c; entext=(entext*entext)%n1; //187->n1 if(a[i]==1) { c=c+1; entext=(entext*ptext)%n1; //187->n1 } } // cout<<" Encrypted 'c' : "<<c; return entext; } int RSA::keygenerate2(int ctext) { //Decryption int i,dntext,c; dntext=1; c=0; decitobin(d); //Private Key with 'd' //b[]->array contains binary value of 'd' for(i=len;i>=0;i--) { c=2*c; dntext=(dntext*dntext)%n1; if(a[i]==1) { c=c+1; dntext=(dntext*ctext)%n1; } } // cout<<" Decrypted 'c' := "<<c; return dntext; } void RSA::decitobin(int x) { int k,i=0; while(x>0) { a[i]=x%2; i++; x=x/2; } //when exit from above loop, i value is incremented by 1 k=i-1; len=i-1; } int RSA::encrypt(int num) { int ctext,i; pt=num; ctext=keygenerate1(num); return(ctext); } int RSA::decrypt(int ctext) { int dectext,i; dectext=keygenerate2(ctext); return(dectext); } //Application File--RSA Application //Miller & Rabin Algorithm--Test for Primality //PseudoRandom Number Generator Algorithm //Relatively Prime--Euclid's Algorithm #include"rh1.h" #include<stdio.h> void main() { int i,det,det1,len,k,k1,cnt; int con=0,c; char ch[100],cipher[20],orig[20]; RSA r; c=1; cout<<endl<<endl; for(i=0;i<70;i++) cout<<'*'; cout<<" RSA APPLICATION "; for(i=0;i<70;i++) cout<<'*'; cout<<endl; r.pseudo1(); r.relprime(); cout<<" Enter the String : "; cnt=0; char chr; scanf ( "%[^ ]s", ch ) ; len=strlen(ch); k=0;k1=0; for(i=0;i<len;i++) { con=(int)ch[i]; det=r.encrypt(con); cipher[k]=char(det); k++; det1=r.decrypt(det); orig[k1]=char(det1); k1++; } cipher[k]='

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