99 lines
2.5 KiB
Java
99 lines
2.5 KiB
Java
package ciphers;
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import java.math.BigInteger;
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import java.security.SecureRandom;
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import javax.swing.JOptionPane;
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/**
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* @author Nguyen Duy Tiep on 23-Oct-17.
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*/
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public final class RSA {
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/**
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* Trivial test program.
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*
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* @param args
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* @deprecated TODO remove main and make JUnit Testing or any other
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* methodology
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*/
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public static void main(String[] args) {
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RSA rsa = new RSA(1024);
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String text1 = JOptionPane.showInputDialog("Enter a message to encrypt :");
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String ciphertext = rsa.encrypt(text1);
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JOptionPane.showMessageDialog(null, "Your encrypted message : " + ciphertext);
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JOptionPane.showMessageDialog(null, "Your message after decrypt : " + rsa.decrypt(ciphertext));
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}
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private BigInteger modulus, privateKey, publicKey;
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/**
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*
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* @param bits
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*/
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public RSA(int bits) {
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generateKeys(bits);
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}
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/**
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*
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* @param message
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* @return encrypted message
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*/
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public synchronized String encrypt(String message) {
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return (new BigInteger(message.getBytes())).modPow(publicKey, modulus).toString();
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}
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/**
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*
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* @param message
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* @return encrypted message as big integer
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*/
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public synchronized BigInteger encrypt(BigInteger message) {
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return message.modPow(publicKey, modulus);
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}
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/**
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*
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* @param encryptedMessage
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* @return plain message
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*/
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public synchronized String decrypt(String encryptedMessage) {
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return new String((new BigInteger(encryptedMessage)).modPow(privateKey, modulus).toByteArray());
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}
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/**
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*
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* @param encryptedMessage
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* @return plain message as big integer
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*/
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public synchronized BigInteger decrypt(BigInteger encryptedMessage) {
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return encryptedMessage.modPow(privateKey, modulus);
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}
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/**
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* Generate a new public and private key set.
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*
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* @param bits
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*/
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public synchronized void generateKeys(int bits) {
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SecureRandom r = new SecureRandom();
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BigInteger p = new BigInteger(bits / 2, 100, r);
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BigInteger q = new BigInteger(bits / 2, 100, r);
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modulus = p.multiply(q);
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BigInteger m = (p.subtract(BigInteger.ONE)).multiply(q.subtract(BigInteger.ONE));
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publicKey = new BigInteger("3");
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while (m.gcd(publicKey).intValue() > 1) {
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publicKey = publicKey.add(new BigInteger("2"));
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}
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privateKey = publicKey.modInverse(m);
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}
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}
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