java rsa 기반의 암호화

@Test

public void test() throws Exception {

// 서버 RSA 생성 및 클라이언트에 공개키 전달

KeyPairGenerator generator = KeyPairGenerator.getInstance("RSA");

generator.initialize(KEY_SIZE);

KeyPair keyPair = generator.genKeyPair();

KeyFactory keyFactory = KeyFactory.getInstance("RSA");

PublicKey publicKey = keyPair.getPublic();

PrivateKey privateKey = keyPair.getPrivate();

// 비밀키

// session.setAttribute("__rsaPrivateKey__", privateKey);

RSAPublicKeySpec publicSpec = keyFactory.getKeySpec(publicKey, RSAPublicKeySpec.class);

String publicKeyModulus = publicSpec.getModulus().toString(16);

String publicKeyExponent = publicSpec.getPublicExponent().toString(16);

// 공개키 정보

// System.out.println(publicKeyModulus);

// System.out.println(publicKeyExponent);

// client

// 공개키 만들기

RSAPublicKeySpec cPublicSpec = new RSAPublicKeySpec(new BigInteger(publicKeyModulus, 16), new BigInteger(publicKeyExponent, 16));

KeyFactory cKeyFactory = KeyFactory.getInstance("RSA");

PublicKey cPublicKey = cKeyFactory.generatePublic(cPublicSpec);

// 공개키 암호화

String password = "aaaa1111";

Cipher cCipher = Cipher.getInstance("RSA");

cCipher.init(Cipher.ENCRYPT_MODE, cPublicKey);

byte[] cArrCipherData = cCipher.doFinal(password.getBytes());

String strCipher = new String(Base64.encodeBase64(cArrCipherData));

// 서버 복호화

Cipher cipher = Cipher.getInstance("RSA");

cipher.init(Cipher.DECRYPT_MODE, privateKey);

byte[] data = cipher.doFinal(Base64.decodeBase64(strCipher));

System.out.println(new String(data));

}

public byte[] hexToByteArray(String hex) {

if (hex == null || hex.length() % 2 != 0) {

return new byte[] {};

}

byte[] bytes = new byte[hex.length() / 2];

for (int i = 0; i < hex.length(); i += 2) {

byte value = (byte) Integer.parseInt(hex.substring(i, i + 2), 16);

bytes[(int) Math.floor(i / 2)] = value;

}

return bytes;

}