java - Java类中RSA加密的问题

Question

public class MyEncrypt {

    public void saveToFile(String fileName, BigInteger mod, BigInteger exp) throws IOException {
        ObjectOutputStream oout = new ObjectOutputStream(new BufferedOutputStream(new FileOutputStream(fileName)));
          try {
                oout.writeObject(mod);
                oout.writeObject(exp);
          } catch (Exception e) {
          throw new IOException("Unexpected error", e);
          } finally {
            oout.close();
          }
    }

    public static void main(String[] args) throws Exception {
                MyEncrypt myEncrypt = new MyEncrypt();
        KeyPairGenerator kpg = KeyPairGenerator.getInstance("RSA");
        kpg.initialize(128);
        KeyPair kp = kpg.genKeyPair();
        RSAPublicKey publicKey = (RSAPublicKey) kp.getPublic();
        RSAPrivateKey privateKey = (RSAPrivateKey) kp.getPrivate();
        KeyFactory fact = KeyFactory.getInstance("RSA");        
        RSAPublicKeySpec pub = fact.getKeySpec(kp.getPublic(), RSAPublicKeySpec.class);
        RSAPrivateKeySpec priv = fact.getKeySpec(kp.getPrivate(), RSAPrivateKeySpec.class);

        myEncrypt.saveToFile("public.key", pub.getModulus(), pub.getPublicExponent());
        myEncrypt.saveToFile("private.key", priv.getModulus(), priv.getPrivateExponent());
        String encString = myEncrypt.bytes2String(myEncrypt.rsaEncrypt("pritesh".getBytes()));
        System.out.println("encrypted : " + encString);
        String decString = myEncrypt.bytes2String(myEncrypt.rsaDecrypt(encString.getBytes()));
        System.out.println("decrypted : " + decString);
    }   

    PublicKey readKeyFromFile(String keyFileName) throws Exception {
      InputStream in = new FileInputStream(keyFileName);
      ObjectInputStream oin = new ObjectInputStream(new BufferedInputStream(in));
      try {
        BigInteger m = (BigInteger) oin.readObject();
        BigInteger e = (BigInteger) oin.readObject();
        RSAPublicKeySpec keySpec = new RSAPublicKeySpec(m, e);
        KeyFactory fact = KeyFactory.getInstance("RSA");
        PublicKey pubKey = fact.generatePublic(keySpec);
        return pubKey;
      } catch (Exception e) {
        throw new RuntimeException("Spurious serialisation error", e);
      } finally {
        oin.close();
      }
    }

    PrivateKey readPrivateKeyFromFile(String keyFileName) throws Exception {
      InputStream in = new FileInputStream(keyFileName);
      ObjectInputStream oin = new ObjectInputStream(new BufferedInputStream(in));
      try {
        BigInteger m = (BigInteger) oin.readObject();
        BigInteger e = (BigInteger) oin.readObject();
        RSAPrivateKeySpec keySpec = new RSAPrivateKeySpec(m, e);
        KeyFactory fact = KeyFactory.getInstance("RSA");
        PrivateKey pubKey = fact.generatePrivate(keySpec);
        return pubKey;
      } catch (Exception e) {
        throw new RuntimeException("Spurious serialisation error", e);
      } finally {
        oin.close();
      }
    }

    public byte[] rsaEncrypt(byte[] data) throws Exception {
      byte[] src = new byte[] { (byte) 0xbe, (byte) 0xef };
      PublicKey pubKey = this.readKeyFromFile("public.key");
      Cipher cipher = Cipher.getInstance("RSA");
      cipher.init(Cipher.ENCRYPT_MODE, pubKey);
      byte[] cipherData = cipher.doFinal(data);
      return cipherData;
    }

    public byte[] rsaDecrypt(byte[] data) throws Exception {
      byte[] src = new byte[] { (byte) 0xbe, (byte) 0xef };
      PrivateKey pubKey = this.readPrivateKeyFromFile("private.key");
      Cipher cipher = Cipher.getInstance("RSA");
      cipher.init(Cipher.DECRYPT_MODE, pubKey);
      byte[] cipherData = cipher.doFinal(data);
      return cipherData;
    }

    private String bytes2String(byte[] bytes) {
        StringBuilder string = new StringBuilder();
        for (byte b: bytes) {
                String hexString = Integer.toHexString(0x00FF & b);
                string.append(hexString.length() == 1 ? "0" + hexString : hexString);
        }
        return string.toString();
    }
}

我收到这个错误:

Exception in thread "main" java.security.InvalidParameterException: RSA keys must be at least 512 bits long
    at sun.security.rsa.RSAKeyPairGenerator.initialize(RSAKeyPairGenerator.java:70)
    at java.security.KeyPairGenerator$Delegate.initialize(KeyPairGenerator.java:631)
    at java.security.KeyPairGenerator.initialize(KeyPairGenerator.java:340)
    at MyEncrypt.main(MyEncrypt.java:42)

我已经从 http://www.javamex.com/tutorials/cryptography/rsa_encryption_2.shtml 示例创建了这个类

---



<p>public class MyEncrypt {</p>

<pre><code>static final String HEXES = "0123456789ABCDEF";
byte[] buf = new byte[1024];

public void saveToFile(String fileName, BigInteger mod, BigInteger exp) throws IOException {
ObjectOutputStream oout = new ObjectOutputStream(new BufferedOutputStream(new FileOutputStream(fileName)));
try {
oout.writeObject(mod);
oout.writeObject(exp);
} catch (Exception e) {
throw new IOException("Unexpected error", e);
} finally {
oout.close();
}
}

public static void main(String[] args) throws Exception {
MyEncrypt myEncrypt = new MyEncrypt();
KeyPairGenerator kpg = KeyPairGenerator.getInstance("RSA");
kpg.initialize(2048);
KeyPair kp = kpg.genKeyPair();
RSAPublicKey publicKey = (RSAPublicKey) kp.getPublic();
RSAPrivateKey privateKey = (RSAPrivateKey) kp.getPrivate();
KeyFactory fact = KeyFactory.getInstance("RSA");
RSAPublicKeySpec pub = fact.getKeySpec(kp.getPublic(), RSAPublicKeySpec.class);
RSAPrivateKeySpec priv = fact.getKeySpec(kp.getPrivate(), RSAPrivateKeySpec.class);

myEncrypt.saveToFile("public.key", pub.getModulus(), pub.getPublicExponent());
myEncrypt.saveToFile("private.key", priv.getModulus(), priv.getPrivateExponent());
String encString = myEncrypt.rsaEncrypt("pritesh");
System.out.println("encrypted : " + encString);
String decString = myEncrypt.rsaDecrypt(encString);
System.out.println("decrypted : " + decString);

String main_file_path = "resume.doc";
String main_encrypt_file_path = "encrypt.doc";
String main_decrypt_file_path = "decrypt.doc";

myEncrypt.rsaEncrypt(new FileInputStream(main_file_path),new FileOutputStream(main_encrypt_file_path));
// Decrypt
myEncrypt.rsaDecrypt(new FileInputStream(main_encrypt_file_path),new FileOutputStream(main_decrypt_file_path));
}

PublicKey readKeyFromFile(String keyFileName) throws Exception {
InputStream in = new FileInputStream(keyFileName);
ObjectInputStream oin = new ObjectInputStream(new BufferedInputStream(in));
try {
BigInteger m = (BigInteger) oin.readObject();
BigInteger e = (BigInteger) oin.readObject();
RSAPublicKeySpec keySpec = new RSAPublicKeySpec(m, e);
KeyFactory fact = KeyFactory.getInstance("RSA");
PublicKey pubKey = fact.generatePublic(keySpec);
return pubKey;
} catch (Exception e) {
throw new RuntimeException("Spurious serialisation error", e);
} finally {
oin.close();
}
}

PrivateKey readPrivateKeyFromFile(String keyFileName) throws Exception {
InputStream in = new FileInputStream(keyFileName);
ObjectInputStream oin = new ObjectInputStream(new BufferedInputStream(in));
try {
BigInteger m = (BigInteger) oin.readObject();
BigInteger e = (BigInteger) oin.readObject();
RSAPrivateKeySpec keySpec = new RSAPrivateKeySpec(m, e);
KeyFactory fact = KeyFactory.getInstance("RSA");
PrivateKey pubKey = fact.generatePrivate(keySpec);
return pubKey;
} catch (Exception e) {
throw new RuntimeException("Spurious serialisation error", e);
} finally {
oin.close();
}
}

public String rsaEncrypt(String plaintext) throws Exception {
PublicKey pubKey = this.readKeyFromFile("public.key");
Cipher cipher = Cipher.getInstance("RSA");
cipher.init(Cipher.ENCRYPT_MODE, pubKey);
byte[] ciphertext = cipher.doFinal(plaintext.getBytes("UTF-8"));
return this.byteToHex(ciphertext);
}

public void rsaEncrypt(InputStream in, OutputStream out) throws Exception {
try {
PublicKey pubKey = this.readKeyFromFile("public.key");
Cipher cipher = Cipher.getInstance("RSA");
cipher.init(Cipher.ENCRYPT_MODE, pubKey);
// Bytes written to out will be encrypted
out = new CipherOutputStream(out, cipher);

// Read in the cleartext bytes and write to out to encrypt
int numRead = 0;
while ((numRead = in.read(buf)) >= 0){
out.write(buf, 0, numRead);
}
out.close();
}
catch (java.io.IOException e){
e.printStackTrace();
}
}

public void rsaDecrypt(InputStream in, OutputStream out) throws Exception {
try {
PrivateKey pubKey = this.readPrivateKeyFromFile("private.key");
Cipher dcipher = Cipher.getInstance("RSA");
dcipher.init(Cipher.DECRYPT_MODE, pubKey);
// Bytes read from in will be decrypted
in = new CipherInputStream(in, dcipher);

// Read in the decrypted bytes and write the cleartext to out
int numRead = 0;
while ((numRead = in.read(buf)) >= 0) {
out.write(buf, 0, numRead);
}
out.close();
} catch (java.io.IOException e) {
e.printStackTrace();
}
}

public String rsaDecrypt(String hexCipherText) throws Exception {
PrivateKey pubKey = this.readPrivateKeyFromFile("private.key");
Cipher cipher = Cipher.getInstance("RSA");
cipher.init(Cipher.DECRYPT_MODE, pubKey);
String plaintext = new String(cipher.doFinal(this.hexToByte(hexCipherText)), "UTF-8");
return plaintext;
}

public static String byteToHex( byte [] raw ) {
if ( raw == null ) {
return null;
}
final StringBuilder hex = new StringBuilder( 2 * raw.length );
for ( final byte b : raw ) {
hex.append(HEXES.charAt((b & 0xF0) >> 4))
.append(HEXES.charAt((b & 0x0F)));
}
return hex.toString();
}

public static byte[] hexToByte( String hexString){
int len = hexString.length();
byte[] ba = new byte[len / 2];
for (int i = 0; i < len; i += 2) {
ba[i/2] = (byte) ((Character.digit(hexString.charAt(i), 16) << 4) + Character.digit(hexString.charAt(i+1), 16));
}
return ba;
}
</code></pre>



}


它适用于文本文件，但对 docx 和视频等文件有任何想法吗？

Answer 1

错误说明了一切:您正在使用 128 的 key 集进行初始化，而 RSA 预计至少为 512。