C# Bouncy Castle 中的 RSA/ECB/OAEPWITHSHA-256ANDMGF1PADDING - 输入对于 RSA 密码来说太大答案

【问题标题】：RSA/ECB/OAEPWITHSHA-256ANDMGF1PADDING in C# Bouncy Castle - input too large for RSA cipherC# Bouncy Castle 中的 RSA/ECB/OAEPWITHSHA-256ANDMGF1PADDING - 输入对于 RSA 密码来说太大
【发布时间】：2020-11-24 14:09:22
【问题描述】：

您好，我正在尝试将一段 Java 代码转换为 C#，以便使用 RSA 密钥进行解密

Java 代码

import javax.crypto.Cipher;
import javax.crypto.spec.OAEPParameterSpec;
import javax.crypto.spec.PSource;

import sun.misc.BASE64Decoder;
public static String decryptWithRSAKey(String encryptedString, Key pk) throws Exception {
        
        Security.addProvider(new org.bouncycastle.jce.provider.BouncyCastleProvider());
        
        Cipher cipher = Cipher.getInstance("RSA/ECB/OAEPWITHSHA-256ANDMGF1PADDING");
        OAEPParameterSpec oaepParameterSpec = new OAEPParameterSpec("SHA-256", "MGF1", MGF1ParameterSpec.SHA256, PSource.PSpecified.DEFAULT);
        cipher.init(Cipher.DECRYPT_MODE, pk,oaepParameterSpec);        
        return new String(cipher.doFinal(new BASE64Decoder().decodeBuffer(encryptedString)),"UTF-8");//1.6.031->rt.jar -> sun.misc.Base64Decoder 
    }

C#代码

using javax.crypto;
using javax.crypto.spec;
using java.security.spec;
using Org.BouncyCastle.Crypto.Engines;
using Org.BouncyCastle.Crypto.Digests;
using Org.BouncyCastle.Crypto.Encodings;
using java.security;
 public static String DecryptWithRSAKey(String encryptedString, Org.BouncyCastle.Crypto.Parameters.RsaKeyParameters pk)
        {
            
            var decrypter = new OaepEncoding(new RsaEngine(), new Sha256Digest(), new Sha256Digest(), null);
            decrypter.Init(false, pk);           
            var encrypted = decrypter.ProcessBlock(System.Text.Encoding.UTF8.GetBytes(encryptedString), 0, encryptedString.Length);            
            return Base64Encoder.Encode(encrypted);            
        }

触发器

PrivateKeyfilePath =PATH TO PRIVATE KEY
RSAPrivateKey privateKey1 = (RSAPrivateKey)objAc.GetPrivate(PrivateKeyfilePath);

var rsaPri1 = new Org.BouncyCastle.Crypto.Parameters.RsaKeyParameters(true, new Org.BouncyCastle.Math.BigInteger(privateKey1.getModulus().ToString()),
                    new Org.BouncyCastle.Math.BigInteger(privateKey1.getPrivateExponent().ToString()));
String decryptedAESKeyString = RSAEncryptionWithAES.DecryptWithRSAKey(encryptedResponseKey, rsaPri1);

运行时我收到一个错误输入对于 RSA 密码来说太大

如何在 C# Bouncy Castle 中正确指定密码 RSA/ECB/OAEPWITHSHA-256ANDMGF1PADDING？

对于与此相关的 RSA 密码，错误输入是否也太大？

【问题讨论】：

标签： java c# rsa bouncycastle

【解决方案1】：

为了使 C# 代码在功能上对应于 Java 代码，在 C# 代码中encryptedString 必须在解密之前进行 Base64 解码（而不是 UTF8 编码）。解密后的数据必须是 UTF8 解码（而不是 Base64 编码）：

public static string DecryptWithRSAKey(string encryptedString, RsaKeyParameters pk)
{
    var decrypter = new OaepEncoding(new RsaEngine(), new Sha256Digest(), new Sha256Digest(), null);
    decrypter.Init(false, pk);
    var encryptedBytes = Convert.FromBase64String(encryptedString);
    var decrypted = decrypter.ProcessBlock(encryptedBytes, 0, encryptedBytes.Length);
    return Encoding.UTF8.GetString(decrypted);
}

【讨论】：