import java.security.Key;
import java.security.KeyFactory;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.SecureRandom;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;
import javax.crypto.Cipher;
public class MoonRsaFullSample {
private static String publicKey = "";
private static String privateKey = "";
public static void main(String[] args) throws Exception {
createRsaGenKey(); // key 생성
String encStr = "가나다라마ABCDefghi되는거냐";
System.out.println(encStr);
String decStr = rsaEnc(encStr);
System.out.println(decStr);
String finalEncStr = rsaDec(decStr);
System.out.println(finalEncStr);
}
/**
* "smart" 를 이용해 random 값을 추출하여 2048bit에 해당하는 키 생성
* @throws Exception
*/
private static void createRsaGenKey() throws Exception{
String pubkey = "smart";
SecureRandom random = new SecureRandom(pubkey.getBytes());
KeyPairGenerator generator = KeyPairGenerator.getInstance("RSA","SunJSSE"); // OK
generator.initialize(2048, random); // 여기에서는 2048 bit 키를 생성하였음
KeyPair pair = generator.generateKeyPair();
Key pubKey = pair.getPublic(); // Kb(pub) 공개키
Key privKey = pair.getPrivate();// Kb(pri) 개인키
System.out.println("pubKeyHex:\n" + byteArrayToHex(pubKey.getEncoded())+"\n");
System.out.println("privKeyHex:\n" + byteArrayToHex(privKey.getEncoded())+"\n");
publicKey = byteArrayToHex(pubKey.getEncoded());
privateKey = byteArrayToHex(privKey.getEncoded());
}
/**
* 암호화
* @param encStr
* @return byteArrayToHex(cipherText)
* @throws Exception
*/
private static String rsaEnc(String encStr) throws Exception{
Cipher cipher = Cipher.getInstance("RSA/ECB/PKCS1PADDING", "SunJCE"); // 알고리즘 명 / Cipher 알고리즘 mode / padding
X509EncodedKeySpec ukeySpec = new X509EncodedKeySpec(hexToByteArray(publicKey));
KeyFactory ukeyFactory = KeyFactory.getInstance("RSA");
PublicKey publickey = null;
try {
// PublicKey에 공용키 값 설정
publickey = ukeyFactory.generatePublic(ukeySpec);
} catch (Exception e) {
e.printStackTrace();
}
byte[] input = encStr.getBytes();
cipher.init(Cipher.ENCRYPT_MODE, publickey);
byte[] cipherText = cipher.doFinal(input);
return byteArrayToHex(cipherText);
}
/**
* 복호화
* @param byteArrayToHex(cipherText) ==> decStr
* @return
* @throws Exception
*/
private static String rsaDec(String decStr) throws Exception{
Cipher cipher = Cipher.getInstance("RSA/ECB/PKCS1PADDING", "SunJCE");
PKCS8EncodedKeySpec rkeySpec = new PKCS8EncodedKeySpec(hexToByteArray(privateKey));
KeyFactory rkeyFactory = KeyFactory.getInstance("RSA");
PrivateKey privateKey = null;
try {
privateKey = rkeyFactory.generatePrivate(rkeySpec);
} catch (Exception e) {
e.printStackTrace();
}
// 복호
cipher.init(Cipher.DECRYPT_MODE, privateKey);
byte[] plainText = cipher.doFinal(hexToByteArray(decStr));
String returnStr = new String(plainText);
return returnStr;
}
// hex string to byte[]
public static byte[] hexToByteArray(String hex) {
if (hex == null || hex.length() == 0) {
return null;
}
byte[] ba = new byte[hex.length() / 2];
for (int i = 0; i < ba.length; i++) {
ba[i] = (byte) Integer.parseInt(hex.substring(2 * i, 2 * i + 2), 16);
}
return ba;
}
// byte[] to hex sting
public static String byteArrayToHex(byte[] ba) {
if (ba == null || ba.length == 0) {
return null;
}
StringBuffer sb = new StringBuffer(ba.length * 2);
String hexNumber;
for (int x = 0; x < ba.length; x++) {
hexNumber = "0" + Integer.toHexString(0xff & ba[x]);
sb.append(hexNumber.substring(hexNumber.length() - 2));
}
return sb.toString();
}
}
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