使用java将RSA公钥导出到PEM String [英] Export RSA public key to PEM String using java

问题描述

所以我使用Spongy Castle（Android）为RSA公钥生成PEM编码字符串，该字符串将上传到服务器。
这就是我目前正在做的事情：

So I'm using Spongy Castle (Android) to generate a PEM encoded string for an RSA public key that will be uploaded to a server. This is what I'm currently doing:

    PublicKey publicKey = keyPair.getPublic();
    StringWriter writer = new StringWriter();
    PemWriter pemWriter = new PemWriter(writer);
    pemWriter.writeObject(new PemObject("RSA PUBLIC KEY", publicKey.getEncoded()));
    pemWriter.flush();
    pemWriter.close();
    return writer.toString();

现在你可能会说我不知道​​如何构建 PemObject 或者如果有更简单的方法可以做到这一点。

Now as you can probably tell I'm not sure how to construct the PemObject or if there is an easier way to do this.

使用Bouncy Case时，我曾经这样做过这样的

When using Bouncy Case I used to do this like this

    StringWriter writer = new StringWriter();
    PEMWriter pemWriter = new PEMWriter(writer);
    pemWriter.writeObject(keyPair.getPublic());
    pemWriter.flush();
    pemWriter.close();
    return writer.toString();

但由于某种原因，Spongy Castle中不存在PEMWriter类

But for some reason the PEMWriter class does not exist in Spongy Castle

推荐答案

那么这可能不是最聪明的方式（或者可能是？），但是在检查了的来源之后PEMWriter 这个类基本上是这样做的：

Ok So this is probably not the smartest way (or maybe it is?) to do it, but after checking out the sources for PEMWriter this class basically does this under the hood:

1. 当调用 writeObject 它创建一个 MiscPEMGenerator的实例



2. MiscPEMGenerator 然后通过检查构造函数参数的类型创建 PemObject ，以下是 MiscPEMGenerator 的摘录来源：

1. when calling writeObject it creates an instance of MiscPEMGenerator

2. MiscPEMGenerator then creates the PemObject by checking the type of the constructor's argument, the following is an excerpt from MiscPEMGenerator's source:

private PemObject createPemObject(Object o){
  ...
  else if (o instanceof PublicKey)
  {
      type = "PUBLIC KEY";

      encoding = ((PublicKey)o).getEncoded();
  }
  ...
  return new PemObject(type, encoding);
}

所以可以从 MiscPEMGenerator 代码看，我唯一要改变的是从RSA PUBLIC KEY到PUBLIC KEY的类型参数。这是最终代码。

So as can be seen from the MiscPEMGenerator code the only thing I had to change was the type parameter from "RSA PUBLIC KEY" to just "PUBLIC KEY". Here is the final code.

PublicKey publicKey = keyPair.getPublic();
StringWriter writer = new StringWriter();
PemWriter pemWriter = new PemWriter(writer);
pemWriter.writeObject(new PemObject("PUBLIC KEY", publicKey.getEncoded()));
pemWriter.flush();
pemWriter.close();
return writer.toString();

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