为什么在Java中加密的RSA字节是变量？

我尝试编写一种混合加密，以在服务器和客户端之间进行通信。因此，我从客户端发送了一个公共RSA密钥，服务器加密了他的AES密钥并将其发送回去。但是，如果我在客户端站点上对其进行解密，则密钥的长度比我发送的密钥长，而且我不知道为什么...

这里的代码：

客户：

socket.getOutputStream().write(security.getKeyPair().getPublic().getEncoded());
byte[] keyBuffer = new byte[512];
socket.getInputStream().read(keyBuffer);
security.setKey(new SecretKeySpec(security.decryptRSA(keyBuffer).getBytes(), "AES"));```
服务器：

byte[] keyBuffer = new byte[550]; this.socket.getInputStream().read(keyBuffer); PublicKey publicKey = KeyFactory.getInstance("RSA").generatePublic(new X509EncodedKeySpec(keyBuffer)); this.socket.getOutputStream().write(this.security.encryptRSA(this.security.getKey().getEncoded(), publicKey));``` 安全类方法：

public byte[] encryptRSA(byte[] message, PublicKey key) {
        byte[] buffer = message;
        try {
            this.cipher = Cipher.getInstance("RSA");
            this.cipher.init(Cipher.ENCRYPT_MODE, key);
            buffer = this.cipher.doFinal(buffer);
        } catch (NoSuchAlgorithmException | NoSuchPaddingException | InvalidKeyException | IllegalBlockSizeException | BadPaddingException e) {
            e.printStackTrace();
        }

        return buffer;
    }


public String decryptRSA(byte[] message) {
        byte[] buffer = message;
        try {
            this.cipher = Cipher.getInstance("RSA");
            this.cipher.init(Cipher.DECRYPT_MODE, this.keyPair.getPrivate());
            buffer = this.cipher.doFinal(buffer);
        } catch (NoSuchAlgorithmException | NoSuchPaddingException | InvalidKeyException | IllegalBlockSizeException | BadPaddingException e) {
            e.printStackTrace();
        }

        return new String(buffer);
    }

谢谢！

问题来源：Stack Overflow