C# 加密/解密大型文件（.NET）

我必须加密、存储然后在以后解密大型文件。最好的方法是什么？我听说RSA加密非常昂贵，建议使用RSA加密AES密钥，然后使用AES密钥加密大型文件。任何有范例的建议都会很好

通常，当数据在一台机器（如服务器）上加密，然后由另一台机器（客户端）解密时，会使用您描述的策略。服务器将使用新生成的密钥使用对称密钥加密（为了性能）对数据进行加密，并使用公钥（与客户端的私钥匹配）对该对称密钥进行加密。服务器向客户端发送加密数据和加密对称密钥。客户端可以使用其私钥解密对称密钥，然后使用此对称密钥解密数据。

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如果您在同一台机器上加密和解密数据，那么同时使用RSA和AES可能没有意义，因为您不会试图将加密密钥传递给另一台机器。

一个有机体的大是另一个有机体的小，尽管我们看到它时都知道它很昂贵。眨眼，眨眼

尝试在您的环境中进行如下基准测试，看看您的情况：

《编辑》2012年2月13日：代码已经更新，因为我（不知不觉地）变得更聪明了，并且注意到一些剪切粘贴错误已经悄悄出现。我有罪

使用系统；
使用System.IO；
使用System.Security.Cryptography；
使用系统文本；
...
//Rfc2898DeriveBytes常量：
公共只读字节[]salt=新字节[]{0x00，0x00，0x00，0x00，0x00，0x00，0x00，0x00，0x00}；//必须至少为8个字节。把这个加盐！
公共常量int迭代次数=1042；//建议大于等于1000。
///解密一个文件。
///注意：“填充无效，无法删除。”是Universal CryptoServices错误。在紧张之前，确保密码、salt和迭代是正确的。
///要解密的文件的完整路径和名称。
///要输出的文件的完整路径和名称。
///解密的密码。
///要应用于密码的salt。
///在为解密生成密钥和初始化向量之前，应使用Rfc2898DeriveBytes的迭代次数。
公共无效解密文件（字符串sourceFilename、字符串destinationFilename、字符串密码、字节[]salt、int迭代次数）
{
aes管理aes=新aes管理（）；
aes.BlockSize=aes.LegalBlockSize[0].MaxSize；
aes.KeySize=aes.LegalKeySizes[0].MaxSize；
//注意：Rfc2898DeriveBytes初始化和对GetBytes的后续调用在加密和解密端都必须完全相同，包括顺序。
Rfc2898DeriveBytes键=新的Rfc2898DeriveBytes（密码、salt、迭代次数）；
aes.Key=Key.GetBytes（aes.KeySize/8）；
aes.IV=key.GetBytes（aes.BlockSize/8）；
aes.Mode=CipherMode.CBC；
ICryptoTransform transform=aes.CreateDecryptor（aes.Key，aes.IV）；
使用（FileStream destination=newfilestream（destinationFilename，FileMode.CreateNew，FileAccess.Write，FileShare.None））
{
使用（CryptoStream CryptoStream=新的CryptoStream（目标、转换、CryptoStreamMode.Write））
{
尝试
{
使用（FileStream source=newfilestream（sourceFilename，FileMode.Open，FileAccess.Read，FileShare.Read））
{
source.CopyTo（加密流）；
}
}
捕获（加密异常）
{
if（exception.Message==“填充无效，无法删除。”）
抛出新的ApplicationException（“通用Microsoft加密异常（不可信！）”，异常；
其他的
投掷；
}
}
}
}
///加密文件。
///要加密的文件的完整路径和名称。
///要输出的文件的完整路径和名称。
///加密的密码。
///要应用于密码的salt。
///在为解密生成密钥和初始化向量之前，应使用Rfc2898DeriveBytes的迭代次数。
public void EncryptFile（字符串sourceFilename、字符串destinationFilename、字符串密码、字节[]salt、int迭代次数）
{
aes管理aes=新aes管理（）；
aes.BlockSize=aes.LegalBlockSize[0].MaxSize；
aes.KeySize=aes.LegalKeySizes[0].MaxSize；
//注意：Rfc2898DeriveBytes初始化和对GetBytes的后续调用在加密和解密端都必须完全相同，包括顺序。
Rfc2898DeriveBytes键=新的Rfc2898DeriveBytes（密码、salt、迭代次数）；
aes.Key=Key.GetBytes（aes.KeySize/8）；
aes.IV=key.GetBytes（aes.BlockSize/8）；
aes.Mode=CipherMode.CBC；
ICryptoTransform transform=aes.CreateEncryptor（aes.Key，aes.IV）；
使用（FileStream destination=newfilestream（destinationFilename，FileMode.CreateNew，FileAccess.Write，FileShare.None））
{
使用（CryptoStream CryptoStream=新的CryptoStream（目标、转换、CryptoStreamMode.Write））
{
使用（FileStream source=newfilestream（sourceFilename，FileMode.Open，FileAccess.Read，FileShare.Read））
{
source.CopyTo（加密流）；
}
}
}
}

正如您所听到的，非对称加密（如RSA）比对称加密（如AES）慢得多，但它确实有它的优点（更简单的密钥管理，如保护单个私钥）

密钥（双关语的目的）是利用两者的优点（非对称私钥和对称速度）

using System;
using System.IO;
using System.Security.Cryptography;
using System.Text;

...

    // Rfc2898DeriveBytes constants:
    public readonly byte[] salt = new byte[] { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 }; // Must be at least eight bytes.  MAKE THIS SALTIER!
    public const int iterations = 1042; // Recommendation is >= 1000.

    /// <summary>Decrypt a file.</summary>
    /// <remarks>NB: "Padding is invalid and cannot be removed." is the Universal CryptoServices error.  Make sure the password, salt and iterations are correct before getting nervous.</remarks>
    /// <param name="sourceFilename">The full path and name of the file to be decrypted.</param>
    /// <param name="destinationFilename">The full path and name of the file to be output.</param>
    /// <param name="password">The password for the decryption.</param>
    /// <param name="salt">The salt to be applied to the password.</param>
    /// <param name="iterations">The number of iterations Rfc2898DeriveBytes should use before generating the key and initialization vector for the decryption.</param>
    public void DecryptFile(string sourceFilename, string destinationFilename, string password, byte[] salt, int iterations)
    {
        AesManaged aes = new AesManaged();
        aes.BlockSize = aes.LegalBlockSizes[0].MaxSize;
        aes.KeySize = aes.LegalKeySizes[0].MaxSize;
        // NB: Rfc2898DeriveBytes initialization and subsequent calls to   GetBytes   must be eactly the same, including order, on both the encryption and decryption sides.
        Rfc2898DeriveBytes key = new Rfc2898DeriveBytes(password, salt, iterations);
        aes.Key = key.GetBytes(aes.KeySize / 8);
        aes.IV = key.GetBytes(aes.BlockSize / 8);
        aes.Mode = CipherMode.CBC;
        ICryptoTransform transform = aes.CreateDecryptor(aes.Key, aes.IV);

        using (FileStream destination = new FileStream(destinationFilename, FileMode.CreateNew, FileAccess.Write, FileShare.None))
        {
            using (CryptoStream cryptoStream = new CryptoStream(destination, transform, CryptoStreamMode.Write))
            {
                try
                {
                    using (FileStream source = new FileStream(sourceFilename, FileMode.Open, FileAccess.Read, FileShare.Read))
                    {
                        source.CopyTo(cryptoStream);
                    }
                }
                catch (CryptographicException exception)
                {
                    if (exception.Message == "Padding is invalid and cannot be removed.")
                        throw new ApplicationException("Universal Microsoft Cryptographic Exception (Not to be believed!)", exception);
                    else
                        throw;
                }
            }
        }
    }

    /// <summary>Encrypt a file.</summary>
    /// <param name="sourceFilename">The full path and name of the file to be encrypted.</param>
    /// <param name="destinationFilename">The full path and name of the file to be output.</param>
    /// <param name="password">The password for the encryption.</param>
    /// <param name="salt">The salt to be applied to the password.</param>
    /// <param name="iterations">The number of iterations Rfc2898DeriveBytes should use before generating the key and initialization vector for the decryption.</param>
    public void EncryptFile(string sourceFilename, string destinationFilename, string password, byte[] salt, int iterations)
    {
        AesManaged aes = new AesManaged();
        aes.BlockSize = aes.LegalBlockSizes[0].MaxSize;
        aes.KeySize = aes.LegalKeySizes[0].MaxSize;
        // NB: Rfc2898DeriveBytes initialization and subsequent calls to   GetBytes   must be eactly the same, including order, on both the encryption and decryption sides.
        Rfc2898DeriveBytes key = new Rfc2898DeriveBytes(password, salt, iterations);
        aes.Key = key.GetBytes(aes.KeySize / 8);
        aes.IV = key.GetBytes(aes.BlockSize / 8);
        aes.Mode = CipherMode.CBC;
        ICryptoTransform transform = aes.CreateEncryptor(aes.Key, aes.IV);

        using (FileStream destination = new FileStream(destinationFilename, FileMode.CreateNew, FileAccess.Write, FileShare.None))
        {
            using (CryptoStream cryptoStream = new CryptoStream(destination, transform, CryptoStreamMode.Write))
            {
                using (FileStream source = new FileStream(sourceFilename, FileMode.Open, FileAccess.Read, FileShare.Read))
                {
                    source.CopyTo(cryptoStream);
                }
            }
        }
    }

/// Encrypts a file using Rijndael algorithm.
///</summary>
///<param name="inputFile"></param>
///<param name="outputFile"></param>
private void EncryptFile(string inputFile, string outputFile)
{

    try
    {
        string password = @"myKey123"; // Your Key Here
        UnicodeEncoding UE = new UnicodeEncoding();
        byte[] key = UE.GetBytes(password);

        string cryptFile = outputFile;
        FileStream fsCrypt = new FileStream(cryptFile, FileMode.Create);

        RijndaelManaged RMCrypto = new RijndaelManaged();

        CryptoStream cs = new CryptoStream(fsCrypt,
            RMCrypto.CreateEncryptor(key, key),
            CryptoStreamMode.Write);

        FileStream fsIn = new FileStream(inputFile, FileMode.Open);

        int data;
        while ((data = fsIn.ReadByte()) != -1)
            cs.WriteByte((byte)data);


        fsIn.Close();
        cs.Close();
        fsCrypt.Close();
    }
    catch
    {
        MessageBox.Show("Encryption failed!", "Error");
    }
}

///
/// Decrypts a file using Rijndael algorithm.
///</summary>
///<param name="inputFile"></param>
///<param name="outputFile"></param>
private void DecryptFile(string inputFile, string outputFile)
{

    {
        string password = @"myKey123"; // Your Key Here

        UnicodeEncoding UE = new UnicodeEncoding();
        byte[] key = UE.GetBytes(password);

        FileStream fsCrypt = new FileStream(inputFile, FileMode.Open);

        RijndaelManaged RMCrypto = new RijndaelManaged();

        CryptoStream cs = new CryptoStream(fsCrypt,
            RMCrypto.CreateDecryptor(key, key),
            CryptoStreamMode.Read);

        FileStream fsOut = new FileStream(outputFile, FileMode.Create);

        int data;
        while ((data = cs.ReadByte()) != -1)
            fsOut.WriteByte((byte)data);

        fsOut.Close();
        cs.Close();
        fsCrypt.Close();

    }
}

void Save()
{
    var encryptedFilePath = Directory.GetCurrentDirectory() + "\\data.bin.aes";
    using(var fileStream = File.Create(encryptedFilePath))
    {
        using (var cryptoStream = Security.FileEncryptor.CreateEncryptor(fileStream, passwordHere))
        {
            var formatter = new BinaryFormatter();
            formatter.Serialize(cryptoStream, myObject);
            cryptoStream.Flush();
        }

    }
}

void Load()
{
    var encryptedFilePath = Directory.GetCurrentDirectory() + "\\data.bin.aes";

    using(var fileStream = File.Open(encryptedFilePath, FileMode.Open))
    {
        using (var cryptoStream = Security.FileEncryptor.CreateDecryptor(fileStream, passwordHere))
        {
            var formatter = new BinaryFormatter();
            var myObject = (myObjectType)formatter.Deserialize(cryptoStream);
        }
    }
}

using System.IO;
using System.Security.Cryptography;
using System;

namespace Security
{

    class FileEncryptor
    {
        public static Stream CreateEncryptor(Stream source, string password)
        {
            byte[] SaltBytes = new byte[16];
            RandomNumberGenerator.Fill(SaltBytes); //RandomNumberGenerator is used for .Net Core 3

            AesManaged aes = new AesManaged();
            aes.BlockSize = aes.LegalBlockSizes[0].MaxSize;
            aes.KeySize = aes.LegalKeySizes[0].MaxSize;

            Rfc2898DeriveBytes key = new Rfc2898DeriveBytes(password, SaltBytes, iterations);
            aes.Key = key.GetBytes(aes.KeySize / 8);

            byte[] IVBytes = new byte[aes.BlockSize / 8];
            RandomNumberGenerator.Fill(IVBytes); //RandomNumberGenerator is used for .Net Core 3
            aes.IV = IVBytes;

            aes.Mode = CipherMode.CBC;
            ICryptoTransform transform = aes.CreateEncryptor(aes.Key, aes.IV);

            //Store/Send the Salt and IV - this can be shared. It's more important that it's very random, than being private.
            source.WriteByte((byte)SaltBytes.Length);
            source.Write(SaltBytes, 0, SaltBytes.Length);
            source.WriteByte((byte)IVBytes.Length);
            source.Write(IVBytes, 0, IVBytes.Length);
            source.Flush();

            var cryptoStream = new CryptoStream(source, transform, CryptoStreamMode.Write);
            return cryptoStream;
        }

        public static Stream CreateDecryptor(Stream source, string password)
        {
            var ArrayLength = source.ReadByte();
            if (ArrayLength == -1) throw new Exception("Salt length not found");
            byte[] SaltBytes = new byte[ArrayLength];
            var readBytes = source.Read(SaltBytes, 0, ArrayLength);
            if (readBytes != ArrayLength) throw new Exception("No support for multiple reads");

            ArrayLength = source.ReadByte();
            if (ArrayLength == -1) throw new Exception("Salt length not found");
            byte[] IVBytes = new byte[ArrayLength];
            readBytes = source.Read(IVBytes, 0, ArrayLength);
            if (readBytes != ArrayLength) throw new Exception("No support for multiple reads");

            AesManaged aes = new AesManaged();
            aes.BlockSize = aes.LegalBlockSizes[0].MaxSize;
            aes.KeySize = aes.LegalKeySizes[0].MaxSize;
            aes.IV = IVBytes;

            Rfc2898DeriveBytes key = new Rfc2898DeriveBytes(password, SaltBytes, iterations);
            aes.Key = key.GetBytes(aes.KeySize / 8);

            aes.Mode = CipherMode.CBC;
            ICryptoTransform transform = aes.CreateDecryptor(aes.Key, aes.IV);

            var cryptoStream = new CryptoStream(source, transform, CryptoStreamMode.Read);
            return cryptoStream;
        }

        public const int iterations = 1042; // Recommendation is >= 1000.
    }
}