RSA 암호화

ByteUtil.java

해당 소스에 사용된 ByteUtil 클래스

TestRsa.java

import java.security.InvalidKeyException;
import java.security.Key;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;
import javax.crypto.BadPaddingException;
import javax.crypto.Cipher;
import javax.crypto.IllegalBlockSizeException;
import javax.crypto.NoSuchPaddingException;
 
public class TestRsa {
    public static void main(String[] args) 
           throws NoSuchAlgorithmException, NoSuchPaddingException, InvalidKeyException, IllegalBlockSizeException, BadPaddingException {
        SecureRandom random = new SecureRandom();
        KeyPairGenerator generator = KeyPairGenerator.getInstance("RSA");
        generator.initialize(2048, random);
 
        KeyPair pair = generator.generateKeyPair();
        Key publicKey = pair.getPublic();
        System.out.println("publicKey = " + publicKey);
 
        Key privateKey = pair.getPrivate();
        System.out.println("privateKey = " + privateKey);
 
        Cipher cipher = Cipher.getInstance("RSA");
        cipher.init(Cipher.ENCRYPT_MODE, publicKey, random);
        
        String text = "RSA 암호화!!";
        System.out.println("원본 : " + text);
 
        // String -> byte 변환
        byte[] t0 = text.getBytes();
        System.out.println("원본 바이트 : " + ByteUtil.toHexString(t0));
        
 
        // 인코딩
        byte[] b0 = cipher.doFinal(t0);
        System.out.println("인코딩 : " + ByteUtil.toHexString(b0));
        
        // 디코딩
        cipher.init(Cipher.DECRYPT_MODE, privateKey);
        byte[] b1 = cipher.doFinal(b0);
        
        System.out.println("디코딩 : " + ByteUtil.toHexString(b1));
        System.out.println("디코딩된 원본:" + new String(b1));
    }
}

########### Console 결과 ###########

publicKey = Sun RSA public key, 2048 bits
  modulus: 24375096591711126055210512185359957069059389332115666685656256009167572767173223522908531449043521360276825613201726594898353846423279278285747007266846094212573914607322409575412719234320181695009686453504284619499201124842375042929556510354483722116550582489225345515352818937465595047638810682064411880791025358297049816845633188104939146545275383717858564379062518328967892129218263037788613461088589973921632894302911326334363077605546489131720190553333874412384419644166222126318457219924457347665925613430947371080765753200018907246728766599325596504477911485731278280070273136297987513034643007577899945186837
  public exponent: 65537
privateKey = sun.security.rsa.RSAPrivateCrtKeyImpl@ffc92d04
원본 : RSA 암호화!!
원본 바이트 : 52534120ec9594ed98b8ed99942121
인코딩 : 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
디코딩 : 52534120ec9594ed98b8ed99942121
디코딩된 원본:RSA 암호화!!