使用RSA Cipher进行线程安全

正如标题所说,我想知道在给定RSA算法的情况下如何在多线程环境中最好地使用Cipher实例.

我已经阅读了关于这个主题的几个问题,以及我收集的内容：

>密码不是线程安全的,因为它在加密/解密时保持内部状态
>如果使用AES,则doFinal()会将初始化向量重置为上一个已知值,因此每次都应生成新的Cipher实例

我的问题

>如果选择的算法是RSA,是否只能调用一次cipher.init()？这与第二个子弹相反,如下面的代码所示.我相信因为没有初始化向量.此外,密码仅用于解密数据.
>我应该只在cipher.doFinal()调用上同步吗？
>如果我将密码池作为某个代理后面的阻塞队列,那么处理多个线程请求加密服务的常用方法是什么？

代码示例：

public class RsaPrototype {

private static PrivateKey privKey;
private static Cipher cipher;
private static final String PRIVATE_KEY_PATH ="./privK.pem";

/*
 * ALGORITHM/BLOCKING_MODE/PADDING_SCHEMA
 */
private static final String CIPHER_SPECIFICATION = "RSA/None/NoPadding";
private static final String RSA_PROVIDER ="BC";

static {

    Security.addProvider(new BouncyCastleProvider());
    importPrivateKey();
    cipher = getCipher();

}

/**
 * Initializes cipher with RSA algorithm,without blocking mode and padding.
 * Implementation provider is bouncy castle.
 * 
 * @return cipher instance.
 */
private static Cipher getCipher() {

    try 
    {

            Cipher cipher = Cipher.getInstance(CIPHER_SPECIFICATION,RSA_PROVIDER);
            cipher.init(Cipher.DECRYPT_MODE,privKey);
            return cipher;

    } catch (NoSuchAlgorithmException | NoSuchPaddingException | NoSuchProviderException e) {

        throw new RuntimeException(e.getMessage());
    }
}

/**
 * Imports public key from the given .PEM file into application cache.
 */
private static void importPrivateKey() {

    try (BufferedReader reader = 
            new BufferedReader(new FileReader(PRIVATE_KEY_PATH));

        PEMParser pemParser = 
            new PEMParser(reader);) {


        privKey = new JcaPEMKeyConverter().getPrivateKey((PrivateKeyInfo) pemParser.readObject());
    }

    catch (IOException ignorable) {
         // not handled
        }
    }

public static String decrypt(byte[] encryptedText) {

    byte[] plainText;

    synchronized (cipher) {

         plainText = cipher.doFinal(encryptedText);
    }

    return new String(plainText,StandardCharsets.UTF_8);
  }
}