Java/ciphers/RSA.java at master · QiuMM/Java · GitHub

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packageciphers;

importjava.math.BigInteger;
importjava.security.SecureRandom;
importjavax.swing.JOptionPane;

/**
 * @author Nguyen Duy Tiep on 23-Oct-17.
 */
publicfinalclassRSA {

/**
 * Trivial test program.
 *
 * @param args
 * @deprecated TODO remove main and make JUnit Testing or any other
 * methodology
 */
publicstaticvoidmain(String[] args) {

RSArsa = newRSA(1024);
Stringtext1 = JOptionPane.showInputDialog("Enter a message to encrypt :");

Stringciphertext = rsa.encrypt(text1);
JOptionPane.showMessageDialog(null, "Your encrypted message : " + ciphertext);

JOptionPane.showMessageDialog(null, "Your message after decrypt : " + rsa.decrypt(ciphertext));
 }

privateBigIntegermodulus, privateKey, publicKey;

/**
 *
 * @param bits
 */
publicRSA(intbits) {
generateKeys(bits);
 }

/**
 *
 * @param message
 * @return encrypted message
 */
publicsynchronizedStringencrypt(Stringmessage) {
return (newBigInteger(message.getBytes())).modPow(publicKey, modulus).toString();
 }

/**
 *
 * @param message
 * @return encrypted message as big integer
 */
publicsynchronizedBigIntegerencrypt(BigIntegermessage) {
returnmessage.modPow(publicKey, modulus);
 }

/**
 *
 * @param encryptedMessage
 * @return plain message
 */
publicsynchronizedStringdecrypt(StringencryptedMessage) {
returnnewString((newBigInteger(encryptedMessage)).modPow(privateKey, modulus).toByteArray());
 }

/**
 *
 * @param encryptedMessage
 * @return plain message as big integer
 */
publicsynchronizedBigIntegerdecrypt(BigIntegerencryptedMessage) {
returnencryptedMessage.modPow(privateKey, modulus);
 }

/**
 * Generate a new public and private key set.
 *
 * @param bits
 */
publicsynchronizedvoidgenerateKeys(intbits) {
SecureRandomr = newSecureRandom();
BigIntegerp = newBigInteger(bits / 2, 100, r);
BigIntegerq = newBigInteger(bits / 2, 100, r);
modulus = p.multiply(q);

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

publicKey = newBigInteger("3");

while (m.gcd(publicKey).intValue() > 1) {
publicKey = publicKey.add(newBigInteger("2"));
 }

privateKey = publicKey.modInverse(m);
 }

}