비대칭 암호화

패딩 ( PKCS#1, OAEP ) 

 대칭키와 다르게 암복호화 하는데 개인키, 공개키가 존재한다 

JAVA에서 해당 키를 관리하기 위하여 KeyPair, PublicKey, PrivateKey, KeyPairGenerator ) 클래스를 제공한다 

 

java.security.KeyPair

KeyPair는 공개키 개인 키 쌍을 캡슐화 한 클래스이다, doPublic(), doPrivate() 공개키, 개인키를 반환하는데 쓰인다 

 

java.security.PublicKey

공개키의 인터페이스이다, 

java.security.PrivateKey

개인키의 인터페이스이다 

java.security.KeyPairGenerator 

공개키 개인키 키쌍을 생성하는 방법을 제공한다 

 

공개키 / 개인키 암복호화 예제

import javax.crypto.*;
import java.security.*;
import java.util.Base64;

public class Main {
    public static void main(String[] args) throws NoSuchAlgorithmException, NoSuchPaddingException, InvalidKeyException, IllegalBlockSizeException, BadPaddingException {
       // 대칭키 발행
        KeyGenerator keyGenerator = KeyGenerator.getInstance("Blowfish");
        keyGenerator.init(128);
        Key blowfishKey = keyGenerator.generateKey();
        System.out.println("blowfishKey: "+ Base64.getEncoder().encodeToString(blowfishKey.getEncoded()));

        // 공개키 발행
        KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance("RSA");
        keyPairGenerator.initialize(1024);
        KeyPair keyPair = keyPairGenerator.generateKeyPair();
        PublicKey publicKey = keyPair.getPublic();
        PrivateKey privateKey = keyPair.getPrivate();

        String base64PublicKeyStr = Base64.getEncoder().encodeToString(publicKey.getEncoded());
        String base64PrivateKeyStr = Base64.getEncoder().encodeToString(privateKey.getEncoded());
        System.out.println(base64PublicKeyStr.length()+"/ "+base64PublicKeyStr);
        System.out.println(base64PrivateKeyStr.length()+"/ "+base64PrivateKeyStr);

        Cipher sameKey = Cipher.getInstance("BlowFish/ECB/PKCS5Padding");
        sameKey.init(Cipher.ENCRYPT_MODE, blowfishKey);
        byte[] encryptedData = sameKey.doFinal("test".getBytes());
        System.out.println("encrypted Data: "+Base64.getEncoder().encodeToString(encryptedData));

        Cipher cipher = Cipher.getInstance("RSA/ECB/PKCS1Padding");
        cipher.init(Cipher.ENCRYPT_MODE, publicKey);
        byte[] encrypted = cipher.doFinal(Base64.getEncoder().encodeToString(encryptedData).getBytes());
        StringBuilder sb = new StringBuilder();
        for(byte i : encrypted){
            sb.append(String.format("%02x", i));
        }
        System.out.println("publicKey Encrypted :"+Base64.getEncoder().encodeToString(encrypted));

        cipher.init(Cipher.DECRYPT_MODE, privateKey);
        byte[] decode = cipher.doFinal(encrypted);
        String decodeStr = new String(decode);
        System.out.println("PrivateKe Decrypt: "+decodeStr);

        sameKey.init(Cipher.DECRYPT_MODE, blowfishKey);
        byte[] plainData = sameKey.doFinal(Base64.getDecoder().decode(decodeStr));
        String plainDatStr = new String(plainData);
        System.out.println("plainDatStr: "+plainDatStr);
    }
}

 

blowfishKey: JoIODTTnNr2C/rq3m4Jj/Q==
216/ MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQCYsUnfTSpw3o6LyivqifcPJEvQ2xSGfHZv8T4Ps5XNGRs4IcSHX+oYg6wJHdxvqmKU577oDUJg4c8BgKe2XGdjSNSBAmtqJfCFzkU66XtTp0l+sRFBMHprF8CldsjW+brhAPRU2B/j8z7+VshGQWcBwGk7p+3nSXwIq7ZsXT1oUwIDAQAB
848/ 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
encrypted Data: JZJDyOeyL78=
publicKey Encrypted :VN4khcPzzTSFInzN//BR2+PnQB1HC2DhEaSoIuDxxHSZpz3hUAeIOJyWewJZfd7NqJEzgPRMPSNrFAWRq4LLYqEQZVtCJI/QpKOmSZnJ3NIrC2+XzjOUtYhzWqi9xFHKb9cACKgGhSY3sQXFE33QUOb55RiLmM7ttM2O3j6yIy4=
PrivateKe Decrypt: JZJDyOeyL78=
plainDatStr: test