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package iwa.crypt;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.PrivateKey;
import java.security.PublicKey;
import javax.crypto.Cipher;
import javax.crypto.CipherOutputStream;
public class CryptTest {
public static final int bufSize = 1024;
// 파일 암호화
public void encryptFile(String in, String out) throws Exception {
Cipher cipher = Cipher.getInstance("RSA/ECB/PKCS1Padding");
ObjectInputStream ois = new ObjectInputStream(new FileInputStream("PublicKey.ser"));
PublicKey publicKey = (PublicKey) ois.readObject();
ois.close();
cipher.init(Cipher.ENCRYPT_MODE, publicKey);
FileInputStream fis = new FileInputStream(in);
FileOutputStream fos = new FileOutputStream(out);
CipherOutputStream cos = new CipherOutputStream(fos, cipher);
byte[] buffer = new byte[bufSize];
int length;
while ((length = fis.read(buffer)) != -1)
cos.write(buffer, 0, length);
fis.close();
fos.close();
}
// 파일 복호화
public void decryptFile(String in, String out) throws Exception {
Cipher cipher = Cipher.getInstance("RSA/ECB/PKCS1Padding");
ObjectInputStream ois = new ObjectInputStream(new FileInputStream("PrivateKey.ser"));
PrivateKey privateKey = (PrivateKey) ois.readObject();
ois.close();
cipher.init(Cipher.DECRYPT_MODE, privateKey);
FileInputStream fis = new FileInputStream(in);
FileOutputStream fos = new FileOutputStream(out);
CipherOutputStream cos = new CipherOutputStream(fos, cipher);
byte[] buffer = new byte[bufSize];
int length;
while ((length = fis.read(buffer)) != -1)
cos.write(buffer, 0, length);
fis.close();
fos.close();
}
// 키 생성
public void genKey() throws Exception {
KeyPairGenerator key = KeyPairGenerator.getInstance("RSA");
key.initialize(1024);
KeyPair kp = key.genKeyPair();
PrivateKey privateKey = kp.getPrivate();
PublicKey publicKey = kp.getPublic();
ObjectOutputStream out = new ObjectOutputStream(new FileOutputStream("PrivateKey.ser"));
out.writeObject(privateKey);
out.close();
out = new ObjectOutputStream(new FileOutputStream("PublicKey.ser"));
out.writeObject(publicKey);
out.close();
}
public static void main(String[] args) {
CryptTest c = new CryptTest();
try {
// 키 생성
c.genKey();
// 파일 암호화
c.encryptFile("a.txt", "b.txt");
// 파일 복호화
c.decryptFile("b.txt", "c.txt");
} catch (Exception e) {
e.printStackTrace();
}
}
} | 
CryptTest.java