C# 解密使用 RSA DER 格式公钥的文件
本文关键字：格式 公钥 文件 DER RSA 解密 密使 | 更新日期: 2023-09-27 18:32:09
我见过很多问题，没有一个能真正提供好的答案，或者如果他们尝试，他们会认为提出问题的人并没有问他实际上在问什么。只是为了记录，我不是在问签名、加密或 PEM 文件！
就我而言，我将收到一个小的加密数据文件。它已使用 RSA 密钥对的私钥进行加密。
我可用的公钥是 ASN.1 格式的 DER 文件，它本身不是证书，也没有签名。
在Java中，这很容易，在c#中，据我所知，这是一场噩梦。X509Certificate2 声称"找不到对象"，当我尝试解析它时，键的字节数组。
密钥是使用以下 openSSL 命令生成的：
>openssl genrsa -out private_key.pem 2048
Generating RSA private key, 2048 bit long modulus
...........+++
....................................................................................................
...........................+++
e is 65537 (0x10001)
>openssl pkcs8 -topk8 -inform PEM -outform DER -in private_key.pem -out private_key.der -nocrypt
>openssl rsa -in private_key.pem -pubout -outform DER -out public_key.der
writing RSA key
编辑：我正在尝试的代码：
private byte[] ReadBytesFromStream(string streamName)
{
using (Stream stream = this.GetType().Assembly.GetManifestResourceStream(streamName))
{
byte[] result = new byte[stream.Length];
stream.Read(result, 0, (int) stream.Length);
return result;
}
}
public void LoadPublicKey()
{
byte[] key = ReadBytesFromStream("my.namespace.Resources.public_key.der");
X509Certificate2 myCertificate;
try
{
myCertificate = new X509Certificate2(key);
}
catch (Exception e)
{
throw new CryptographicException(String.Format("Unable to open key file. {0}", e));
}
}
ReadBytesFromStream 方法确实返回正确的字节流，public_key.der 文件是一个嵌入的资源。
只是为了完善这个。下面的代码虽然仍然有点混乱，但它似乎是我可以开始工作的。
我们不能使用公钥在 Windows 中解密消息的原因解释如下：http://www.derkeiler.com/Newsgroups/microsoft.public.dotnet.security/2004-05/0270.html
接下来，您需要 c# 代码中的公钥模数和指数，无论是在文件中还是嵌入，这里真的不是问题。不过，我确实使用 Base64 来包装二进制密钥。我放弃了生成Windows实际导入的密钥。此外，对于我需要的东西，公钥将是一个嵌入式资源。
我遇到的最后一个问题是从键生成的模数在Windows（c#）上不起作用。这篇StackOverflow帖子确实掌握了解决这个问题的关键，Windows中的模数不能包含前导零。安卓应用内计费 点网收货验证（C#）
从Java生成的模数在c#上不起作用。使用该帖子中的stripLeadingZeros代码创建一个有效的公钥模数：
private static byte[] stripLeadingZeros(byte[] a) {
int lastZero = -1;
for (int i = 0; i < a.length; i++) {
if (a[i] == 0) {
lastZero = i;
}
else {
break;
}
}
lastZero++;
byte[] result = new byte[a.length - lastZero];
System.arraycopy(a, lastZero, result, 0, result.length);
return result;
}
对于初学者来说，这就是我生成密钥文件的方式：
$ openssl genrsa -out private_key.pem 2048
$ openssl pkcs8 -topk8 -inform PEM -outform DER -in private_key.pem -out private_key.der -nocrypt
$ openssl rsa -in private_key.pem -pubout -outform DER -out public_key.der
Java 代码：
package com.example.signing;
import java.io.BufferedOutputStream;
import java.io.BufferedReader;
import java.io.DataInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.FileReader;
import java.io.IOException;
import java.security.KeyFactory;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.Signature;
import java.security.interfaces.RSAPrivateKey;
import java.security.interfaces.RSAPublicKey;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;
import jcifs.util.Base64;
public class SigningExample {
private static String PRIVATE_KEY_FILE = "private_key.der";
private static String PUBLIC_KEY_FILE = "public_key.der";
/**
* @param args
*/
public static void main(String[] args) {
SigningExample.sign();
}
private static void sign() {
try {
String text = new String(SigningExample.loadFromFile("message.xml"));
String message = Base64.encode(text.getBytes());
RSAPrivateKey privateKey = PrivateRSAKeyReader.getKeyFile(SigningExample.PRIVATE_KEY_FILE);
RSAPublicKey publicKey = PublicRSAKeyReader.getKeyFile(SigningExample.PUBLIC_KEY_FILE);
byte[] modulusBytes = publicKey.getModulus().toByteArray();
byte[] exponentBytes = publicKey.getPublicExponent().toByteArray();
modulusBytes = SigningExample.stripLeadingZeros(modulusBytes);
String modulusB64 = Base64.encode(modulusBytes);
String exponentB64 = Base64.encode(exponentBytes);
System.out.println("Copy these two into your c# code:");
System.out.println("DotNet Modulus : " + modulusB64);
System.out.println("DotNet Exponent: " + exponentB64);
// Testing
byte[] signature = SigningExample.sign(message.getBytes(), privateKey, "SHA1withRSA");
String signedMessage = message + "'n" + Base64.encode(signature);
SigningExample.saveToBase64File("message.signed", signedMessage.getBytes());
System.out.println("'nMessage :'n" + signedMessage);
String[] newkey = new String(SigningExample.loadFromBase64File("message.signed")).split("''n");
System.out.println("Verified : " + SigningExample.verify(newkey[0].getBytes(), publicKey, "SHA1withRSA", Base64.decode(newkey[1])));
} catch (Exception e) {
e.printStackTrace();
}
}
private static byte[] stripLeadingZeros(byte[] a) {
int lastZero = -1;
for (int i = 0; i < a.length; i++) {
if (a[i] == 0) {
lastZero = i;
} else {
break;
}
}
lastZero++;
byte[] result = new byte[a.length - lastZero];
System.arraycopy(a, lastZero, result, 0, result.length);
return result;
}
private static byte[] sign(byte[] data, PrivateKey prvKey,
String sigAlg) throws Exception {
Signature sig = Signature.getInstance(sigAlg);
sig.initSign(prvKey);
sig.update(data, 0, data.length);
return sig.sign();
}
private static boolean verify(byte[] data, PublicKey pubKey,
String sigAlg, byte[] sigbytes) throws Exception {
Signature sig = Signature.getInstance(sigAlg);
sig.initVerify(pubKey);
sig.update(data, 0, data.length);
return sig.verify(sigbytes);
}
public static void saveToBase64File(String fileName, byte[] data) throws IOException {
BufferedOutputStream out = new BufferedOutputStream(new FileOutputStream(fileName));
try {
String b64 = Base64.encode(data);
int lineLength = 64;
int idx = 0;
int len = b64.length();
while (len - idx >= lineLength) {
out.write(b64.substring(idx, idx + lineLength).getBytes());
out.write(''n');
idx += lineLength;
}
out.write(b64.substring(idx, len).getBytes());
} catch (Exception e) {
throw new IOException("Unexpected error", e);
} finally {
out.close();
}
}
public static byte[] loadFromBase64File(String fileName) throws IOException {
BufferedReader br = new BufferedReader(new FileReader(fileName));
try {
StringBuffer sb = new StringBuffer();
String buffer;
while ((buffer = br.readLine()) != null) {
sb.append(buffer);
}
return Base64.decode(sb.toString());
} catch (Exception e) {
throw new IOException("Unexpected error", e);
} finally {
br.close();
}
}
public static void saveToFile(String fileName, byte[] data) throws IOException {
BufferedOutputStream out = new BufferedOutputStream(new FileOutputStream(fileName));
try {
out.write(data);
} catch (Exception e) {
throw new IOException("Unexpected error", e);
} finally {
out.close();
}
}
public static byte[] loadFromFile(String fileName) throws IOException {
BufferedReader br = new BufferedReader(new FileReader(fileName));
try {
StringBuffer sb = new StringBuffer();
String buffer;
while ((buffer = br.readLine()) != null) {
sb.append(buffer);
}
return sb.toString().getBytes();
} catch (Exception e) {
throw new IOException("Unexpected error", e);
} finally {
br.close();
}
}
}
class PrivateRSAKeyReader {
public static RSAPrivateKey getKeyFile(String filename) throws Exception {
File f = new File(filename);
FileInputStream fis = new FileInputStream(f);
DataInputStream dis = new DataInputStream(fis);
byte[] keyBytes = new byte[(int) f.length()];
dis.readFully(keyBytes);
dis.close();
return PrivateRSAKeyReader.generateKey(keyBytes);
}
public static RSAPrivateKey getKey(String base64) throws Exception {
byte[] keyBytes = Base64.decode(base64);
return PrivateRSAKeyReader.generateKey(keyBytes);
}
private static RSAPrivateKey generateKey(byte[] keyBytes) throws Exception {
PKCS8EncodedKeySpec spec = new PKCS8EncodedKeySpec(keyBytes);
return (RSAPrivateKey) KeyFactory.getInstance("RSA").generatePrivate(spec);
}
}
class PublicRSAKeyReader {
public static RSAPublicKey getKeyFile(String filename) throws Exception {
File f = new File(filename);
FileInputStream fis = new FileInputStream(f);
DataInputStream dis = new DataInputStream(fis);
byte[] keyBytes = new byte[(int) f.length()];
dis.readFully(keyBytes);
dis.close();
return PublicRSAKeyReader.generateKey(keyBytes);
}
public static RSAPublicKey getKey(String base64) throws Exception {
byte[] keyBytes = Base64.decode(base64);
return PublicRSAKeyReader.generateKey(keyBytes);
}
private static RSAPublicKey generateKey(byte[] keyBytes) throws Exception {
X509EncodedKeySpec spec = new X509EncodedKeySpec(keyBytes);
return (RSAPublicKey) KeyFactory.getInstance("RSA").generatePublic(spec);
}
}
在 c# 中，此代码片段应该执行以下技巧：
String signedMessage = ""; // load Base64 coded the message generated in Java here.
byte[] message = Convert.FromBase64String(signedMessage);
String messageString = Encoding.ASCII.GetString(message);
String[] lines = Regex.Split(messageString, "'n");
byte[] content = Convert.FromBase64String(lines[0]); // first line of the message were the content
byte[] signature = Convert.FromBase64String(lines[1]); // second line were the signature
RSACryptoServiceProvider rsaObj = new RSACryptoServiceProvider(2048);
//Create a new instance of the RSAParameters structure.
RSAParameters rsaPars = new RSAParameters();
rsaPars.Modulus = Convert.FromBase64String("insert your modulus revealed in the Java example here");
rsaPars.Exponent = Convert.FromBase64String("AQAB"); // Exponent. Should always be this.
// Import key parameters into RSA.
rsaObj.ImportParameters(rsaPars);
// verify the message
Console.WriteLine(rsaObj.VerifyData(Encoding.ASCII.GetBytes(lines[0]), "SHA1", signature));
代码使用 ：
using System.Security;
using System.Security.Cryptography;
using System.Security.Cryptography.X509Certificates;
using System.Text;
我坦率地承认，将最终消息打包到Base64的另一层中有点矫枉过正，应该进行更改。