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  1. /* package whatever; // don't place package name! */
  2. //RSA ENCRYPTION AND DECRYPTION 
  3. import java.util.*;
  4. import java.lang.*;
  5. import java.io.*;
  6.  
  7. /* Name of the class has to be "Main" only if the class is public. */
  8. class Ideone
  9. {
  10. 	public static void main (String[] args) throws java.lang.Exception
  11. 	{
  12. 		int p,q,n,c,d,u,e,m,l,m1;
  13. 		String message = "hide";
  14. 		String ans="";
  15. 		String ctext="";
  16. 		int i=0;
  17. 		l = message.length();
  18. 		System.out.println("message is  "+message);
  19. 		while(i <l)
  20. 		{
  21. 		m =message.charAt(i)-'a' ;
  22.                         i++;
  23.  
  24. 		p= 3;
  25. 		q = 7;
  26. 		e = 2;
  27. 		n = p*q;
  28. 		//System.out.println("value of n "+n);
  29. 		u = (p-1)*(q-1);
  30. 	//	System.out.println("value of u "+u); 
  31.  
  32.  
  33. 		 while (e < u)
  34.     {
  35.  
  36.         if (gcd(e,u)==1)
  37.             break;
  38.         else
  39.             e++;
  40.     }
  41.  
  42.  
  43. //System.out.println("value of e "+e);	
  44. 		d = solve(e,u);
  45.  
  46. 		if(d<0)
  47. 	d = (d+u)%u;
  48. 	//System.out.println("d value obtained is"+d);
  49.  
  50. 	c = ((int)Math.pow(m,d))%n;
  51. 		ctext += (char)(c+97);
  52. 	//System.out.println("encrypted text is"+c);
  53. 	m1 =  ((int)Math.pow(c,e))%n;
  54. 	//	System.out.println("decrypted text is"+m);
  55. 	ans += (char)(m1+97);
  56. 	}
  57. 		System.out.println("encrypted text is   -"+ctext);
  58. 	System.out.println("decrypted text is   -"+ans);
  59. 	int v = verifyalgo(ans,message);
  60. 	if(v == 1)
  61. 	System.out.println("Bob sent the message");
  62. 	else
  63. 		System.out.println("Alice sent the message");
  64.  
  65.  
  66. 	}
  67.  
  68. 	     public static  int solve(int  a, int b)
  69.     {
  70.         int x = 0, y = 1, lastx = 1, lasty = 0, temp;
  71.         while (b != 0)
  72.         {
  73.            int q = a / b;
  74.            int  r = a % b;
  75.  
  76.             a = b;
  77.             b = r;
  78.  
  79.             temp = x;
  80.             x = lastx - q * x;
  81.             lastx = temp;
  82.  
  83.  
  84.         }
  85.        return lastx;
  86.     }
  87.  
  88.  
  89.        public static int verifyalgo(String m1 ,String m)
  90. {
  91.  
  92. 	//System.out.println(m1.compareTo(m));
  93.    if(m1.compareTo(m)==0)
  94.    return 1;
  95.    else
  96.    return 0;
  97. }
  98.  
  99.  
  100.    public static int gcd(int a, int h)
  101. {
  102.     int temp;
  103.     while (true)
  104.     {
  105.         temp = a%h;
  106.         if (temp == 0)
  107.           return h;
  108.         a = h;
  109.         h = temp;
  110.     }
  111. }
  112.  
  113.  
  114. }
Success #stdin #stdout 0.04s 4386816KB
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stdin
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Standard input is empty
stdout
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message is  hide
encrypted text is   -himq
decrypted text is   -hide
Bob sent the message
https://ideone.com/GnCOGI
language:
Java (HotSpot 12)
created:
6 years ago
visibility:
public

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