125 lines
2.2 KiB
Java
125 lines
2.2 KiB
Java
import java.math.BigInteger;
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import java.util.Random;
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import java.io.*;
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public class RSA {
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private BigInteger p;
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private BigInteger q;
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private BigInteger N;
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private BigInteger phi;
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private BigInteger e;
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private BigInteger d;
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private int bitlength = 1024;
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private int blocksize = 256;
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//blocksize in byte
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private Random r;
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public RSA() {
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r = new Random();
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p = BigInteger.probablePrime(bitlength, r);
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q = BigInteger.probablePrime(bitlength, r);
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N = p.multiply(q);
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phi = p.subtract(BigInteger.ONE).multiply(q.subtract(BigInteger.ONE));
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e = BigInteger.probablePrime(bitlength/2, r);
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while (phi.gcd(e).compareTo(BigInteger.ONE) > 0 && e.compareTo(phi) < 0 ) {
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e.add(BigInteger.ONE);
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}
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d = e.modInverse(phi);
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}
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public RSA(BigInteger e, BigInteger d, BigInteger N) {
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this.e = e;
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this.d = d;
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this.N = N;
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}
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public static void main (String[] args) throws IOException {
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RSA rsa = new RSA();
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DataInputStream in=new DataInputStream(System.in);
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String teststring ;
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System.out.println("Enter the plain text:");
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teststring=in.readLine();
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System.out.println("Encrypting String: " + teststring);
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System.out.println("String in Bytes: " + bytesToString(teststring.getBytes()));
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// encrypt
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byte[] encrypted = rsa.encrypt(teststring.getBytes());
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System.out.println("Encrypted String in Bytes: " + bytesToString(encrypted));
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// decrypt
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byte[] decrypted = rsa.decrypt(encrypted);
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System.out.println("Decrypted String in Bytes: " + bytesToString(decrypted));
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System.out.println("Decrypted String: " + new String(decrypted));
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}
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private static String bytesToString(byte[] encrypted) {
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String test = "";
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for (byte b : encrypted) {
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test += Byte.toString(b);
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}
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return test;
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}
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//Encrypt message
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public byte[] encrypt(byte[] message) {
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return (new BigInteger(message)).modPow(e, N).toByteArray();
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}
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// Decrypt message
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public byte[] decrypt(byte[] message) {
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return (new BigInteger(message)).modPow(d, N).toByteArray();
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}
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} |