[Java] I am to complete this RSA class to make it work. Complete To Dos also tak

Question

[Java]

I am to complete this RSA class to make it work. Complete To Dos also take input from Input.txt file such as

Input.txt

e= 103687
p= 1413297339818079839
q= 7795673610480062959
message= gravitatio

--------------------------

import java.io.*;

import java.util.*;

import java.math.BigInteger;

public class RSA_assignment

{

static Scanner console = new Scanner (System.in);

public static void main(String [] args) throws FileNotFoundException

{

System.out.println("Q. How to say hello on Java? : A. Hello Java!!!");

System.out.println("Q. How to say hello on C++? : A. Hello C++!!!");

Scanner inFile = new Scanner (new FileReader("Kamilla2.txt"));

long p,q;

long e;

String ggg;

ggg= inFile.next(); //e-

e=inFile.nextInt();

ggg= inFile.next(); //p=

p=inFile.nextLong();

ggg= inFile.next(); //q=

q=inFile.nextLong();

if ((p-1)%e==0||(q-1)%e==0) {System.out.println("I must choose another e from teacher's website");}

else{ System.out.println("gcd(e,(p-1)(q-1))=1");

  

BigInteger nBI= BobCalculateN(p, q);  

BigInteger eBI= new BigInteger(""+e);

System.out.println("p="+p+" q="+q);

BigInteger dBI=BobCalculateD(p, q, e );

System.out.println("dBI="+dBI);

String mStr; //message

long m; //coded value as for a=01,b=02,.. z=26

// if a is first it coded 1, etc.

ggg= inFile.next(); //message=

String mmm=inFile.next();

System.out.println("message="+mmm);

mStr=getCode(mmm);

System.out.println("mStr="+mStr);

m= Long.parseLong(mStr); //work only for 9-10 letters long   

BigInteger mBI=new BigInteger(""+m);

String c;

BigInteger cBI = mBI.modPow(eBI,nBI);

// c is encrypted message to post nBI n-to post

System.out.print("n= ");

System.out.print(nBI);

System.out.println();

System.out.print("e= ");

System.out.print(eBI);

System.out.println();

System.out.print("c= ");

System.out.print(cBI);

System.out.println();

System.out.print("m= ");

System.out.print(mBI);

System.out.println();

// PrintWriter outFile = new PrintWriter("Encripted.txt");

// I will get encrypted c from somebody , d and n are mine   

BigInteger decryptedmBI=cBI.modPow(dBI, nBI); //decrypted message

// outFile.println(cBI);

// outFile.println(decriptedmBI);

System.out.print("mBI= ");

System.out.println(mBI);

System.out.print("decryptedmBI= ");

System.out.println(decryptedmBI);

String decriptedStr=decryptedmBI.toString();

System.out.println(decriptedStr);

//Print decoded message on meaningful English

PrintLetters(decriptedStr);

inFile.close();

// outFile.close();

}

}

public static long findPrime()

{

//ToDo

long p=0;

return p;

}

public static void PrintLetters(String decriptedStr)

{

//ToDo

}

public static void getCodeOfLetters(String str)

{

//todo

}

public static String getCode(String str)

{

//ToDo

String temp="1";

return temp;

}

public static BigInteger BobCalculateD(long p, long q, long e )

{

//ToDo

BigInteger dBI=new BigInteger(""+0);

return dBI;

}

public static BigInteger BobCalculateN(long p, long q)

{

//ToDo

BigInteger nBI= new BigInteger(""+p);

return nBI;

}

}

The goal is to produce something like this output(Doesn't have to be exact) after reading values from file

e= 103687
p= 1413297339818079839
q= 7795673610480062959
message= gravitatio

n=11017604775781478904665244719208583601
d=5452326099268946397172763409398791927
m==7180122092001200915
c==6365888847651359082866965196518212910
decriptedmBI=7180122092001200915

Explanation / Answer

I had written code for RSA .

As you asked above user has to give the input for e,p,q,message based on them RSA applies and gives the result.

Hope this helps Thankyou.....:)

import java.math.BigInteger;

import java.util.*;

import java.io.*;

public class RSA {

private BigInteger p;

private BigInteger q;

private BigInteger N;

private BigInteger phi;

private BigInteger e;

private BigInteger d;

private int bitlength = 1024;

private int blocksize = 256;

//blocksize in byte

private Random r;

public RSA() {

r = new Random();

Scanner in = new Scanner(System.in);

System.out.print("Enter e value:");

e=in.nextBigInteger();

System.out.print("Enter p value:");

p=in.nextBigInteger();

System.out.print("Enter q value:");

q=in.nextBigInteger();

N = p.multiply(q);

phi = p.subtract(BigInteger.ONE).multiply(q.subtract(BigInteger.ONE));

while (phi.gcd(e).compareTo(BigInteger.ONE) > 0 && e.compareTo(phi) < 0 ) {

e.add(BigInteger.ONE);

}

d = e.modInverse(phi);

}

public RSA(BigInteger e, BigInteger d, BigInteger N) {

this.e = e;

this.d = d;

this.N = N;

}

public static void main (String[] args) throws IOException {

RSA rsa = new RSA();

DataInputStream in=new DataInputStream(System.in);

String teststring ;

System.out.print("Enter the plain text:");

teststring=in.readLine();

System.out.println("Encrypting String: " + teststring);

System.out.println("String in Bytes: " + bytesToString(teststring.getBytes()));

// encrypt

byte[] encrypted = rsa.encrypt(teststring.getBytes());

System.out.println("Encrypted String in Bytes: " + bytesToString(encrypted));

// decrypt

byte[] decrypted = rsa.decrypt(encrypted);

System.out.println("Decrypted String in Bytes: " + bytesToString(decrypted));

System.out.println("Decrypted String: " + new String(decrypted));

}

private static String bytesToString(byte[] encrypted) {

String test = "";

for (byte b : encrypted) {

test += Byte.toString(b);

}

return test;

}

//Encrypt message

public byte[] encrypt(byte[] message) {

return (new BigInteger(message)).modPow(e, N).toByteArray();

}

// Decrypt message

public byte[] decrypt(byte[] message) {

return (new BigInteger(message)).modPow(d, N).toByteArray();

}

}

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