android - java : How can I generate PrivateKey from a string?

Question

我正在尝试使用 SH1 RSA 对消息进行编码，但除了有关 RSA 的一些基本信息外，我没有安全主题方面的经验。我得到了一个作为 String 的私钥。我已经设法编写了以下代码块来完成这项工作，但我不确定我是否安全且正确地完成了这项工作。

我不是专家，但我猜将我的私钥作为字符串放入代码中并不安全。谁能指导我？

String privateKeyString = "mykeyhere...";
byte[] privateKeyBytes = privateKeyString.getBytes();
String encodedPrivateKey = Base64.encodeToString(privateKeyBytes, Base64.URL_SAFE);

KeyFactory factory = KeyFactory.getInstance(RSA);
PKCS8EncodedKeySpec keySpec = new PKCS8EncodedKeySpec(encodedPrivateKey.getBytes());
RSAPrivateKey privateKey = (RSAPrivateKey) factory.generatePrivate(keySpec);

Signature instance = Signature.getInstance(ALGORITHM);
instance.initSign(privateKey);
instance.update(content.getBytes());
return new String(instance.sign());

我的私钥格式如下:

"-----BEGIN PRIVATE KEY-----\n"+
"MIIE...\n"+
"cH0iRj...\n"+
"O0Hhj...\n"+
.
.
.
"fG6...\n"+
"B6/hF...\n"+
"3Mq38...\n"+
"-----END PRIVATE KEY-----\n"

Answer 1

您的 key 格式是 unencrypted base64-encoded PKCS8-encoded private key .这是如何将其解码为私钥的示例。 (在这个例子中不用担心私钥的安全性，这只是例子的一次性)。

import java.io.*;
import java.security.KeyFactory;
import java.security.PrivateKey;
import java.security.spec.PKCS8EncodedKeySpec;
import android.util.Base64;

public class ReadPKCS8Pem {

    private final static String PRIVATE_KEY = 
            "-----BEGIN PRIVATE KEY-----\n"
            + "MIICdQIBADANBgkqhkiG9w0BAQEFAASCAl8wggJbAgEAAoGBAM7t8Ub1DP+B91NJ\n"
            + "nC45zqIvd1QXkQ5Ac1EJl8mUglWFzUyFbhjSuF4mEjrcecwERfRummASbLoyeMXl\n"
            + "eiPg7jvSaz2szpuV+afoUo9c1T+ORNUzq31NvM7IW6+4KhtttwbMq4wbbPpBfVXA\n"
            + "IAhvnLnCp/VyY/npkkjAid4c7RoVAgMBAAECgYBcCuy6kj+g20+G5YQp756g95oN\n"
            + "dpoYC8T/c9PnXz6GCgkik2tAcWJ+xlJviihG/lObgSL7vtZMEC02YXdtxBxTBNmd\n"
            + "upkruOkL0ElIu4S8CUwD6It8oNnHFGcIhwXUbdpSCr1cx62A0jDcMVgneQ8vv6vB\n"
            + "/YKlj2dD2SBq3aaCYQJBAOvc5NDyfrdMYYTY+jJBaj82JLtQ/6K1vFIwdxM0siRF\n"
            + "UYqSRA7G8A4ga+GobTewgeN6URFwWKvWY8EGb3HTwFkCQQDgmKtjjJlX3BotgnGD\n"
            + "gdxVgvfYG39BL2GnotSwUbjjce/yZBtrbcClfqrrOWWw7lPcX1d0v8o3hJfLF5dT\n"
            + "6NAdAkA8qAQYUCSSUwxJM9u0DOqb8vqjSYNUftQ9dsVIpSai+UitEEx8WGDn4SKd\n"
            + "V8kupy/gJlau22uSVYI148fJSCGRAkBz+GEHFiJX657YwPI8JWHQBcBUJl6fGggi\n"
            + "t0F7ibceOkbbsjU2U4WV7sHyk8Cei3Fh6RkPf7i60gxPIe9RtHVBAkAnPQD+BmND\n"
            + "By8q5f0Kwtxgo2+YkxGDP5bxDV6P1vd2C7U5/XxaN53Kc0G8zu9UlcwhZcQ5BljH\n"
            + "N24cUWZOo+60\n"
            + "-----END PRIVATE KEY-----";
    
    public static void main(String[] args) throws Exception {
        // Read in the key into a String
        StringBuilder pkcs8Lines = new StringBuilder();
        BufferedReader rdr = new BufferedReader(new StringReader(PRIVATE_KEY));
        String line;
        while ((line = rdr.readLine()) != null) {
            pkcs8Lines.append(line);
        }
        
        // Remove the "BEGIN" and "END" lines, as well as any whitespace
        
        String pkcs8Pem = pkcs8Lines.toString();
        pkcs8Pem = pkcs8Pem.replace("-----BEGIN PRIVATE KEY-----", "");
        pkcs8Pem = pkcs8Pem.replace("-----END PRIVATE KEY-----", "");
        pkcs8Pem = pkcs8Pem.replaceAll("\\s+","");
        
        // Base64 decode the result
        
        byte [] pkcs8EncodedBytes = Base64.decode(pkcs8Pem, Base64.DEFAULT);
        
        // extract the private key
        
        PKCS8EncodedKeySpec keySpec = new PKCS8EncodedKeySpec(pkcs8EncodedBytes);
        KeyFactory kf = KeyFactory.getInstance("RSA");
        PrivateKey privKey = kf.generatePrivate(keySpec);
        System.out.println(privKey);
    }

}