加密/解密大文件(.NET)
本文关键字：NET 文件 解密 加密 | 更新日期: 2023-09-27 18:24:01
我必须加密、存储大文件，然后再解密。最好的方法是什么？我听说RSA加密很昂贵，建议使用RSA加密AES密钥，然后使用AES密钥加密大型文件。任何有例子的建议都会很棒。
一个生物体的大就是另一个生物体小，尽管我们看到它时都知道它很贵。Wink，Wink。
尝试在您的环境中进行类似以下的基准测试，看看您所处的位置：
2012年2月13日编辑：代码已经更新，因为我变得（不知不觉地）更聪明了，还注意到了一些偷拍错误。真是罪有应得
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);
}
}
}
}
这可能有助于
/// 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();
}
}
来源：http://www.codeproject.com/Articles/26085/File-Encryption-and-Decryption-in-C
通常，当数据在一台机器上（如服务器）加密，然后由另一台机器（客户端）解密时，会使用您所描述的策略。服务器将使用新生成的密钥使用对称密钥加密（为了提高性能）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的数据和加密的对称密钥。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。如果您在同一台机器上对数据进行加密和解密，则同时使用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。
正如您所听到的，非对称密码学，如RSA，比对称密码学（如AES）慢得多，但它确实有的优点（更简单的密钥管理，如要保护的单个私钥）。
密钥（双关语）是利用两者的优点（非对称的私钥和对称的速度），而忽略了另一个的不便（密钥多，速度慢）。
您可以通过每个文件使用一次RSA（不会对性能产生巨大影响）来加密用于加密（更快）大型文件的（对称）密钥来做到这一点。对称密钥的*包装使您只能管理单个私钥。
这里有一个链接到我以前的（但仍然是真实的）博客文章，它给出了一个使用C#和.NET框架（微软的Mono）实现这一点的例子。
RSA
的确，非对称密码学（RSA、ECC等）比对称密码学（AES、ChaCha20等）慢。RSA和其他技术非常适合保护随机对称密钥（或建立一个）。AES和其他技术非常适合与完整性检查（HMAC）一起使用的高效加密。
重要的是，成熟的对称密码没有任何已知的理论弱点。除非攻击者拥有对称密钥，否则无法破坏加密。目前，所有成熟的非对称密码学（RSA，ECC）都基于数学特性，这些特性很容易被未来的量子计算机破解（如果真的出现的话）。
此外，公钥/私钥的处理也成了一个问题。人类记住密码很简单——他们的大脑不会被黑客入侵。对于公钥/私钥，它们需要存储在某个地方。特别是私钥是敏感的。计算机具有TDM组件，可以创建和存储独立于CPU的公钥/私钥。这使用起来非常复杂。
因此，考虑到这一点，只有在绝对必要的情况下才应该使用RSA。
AES
这是我最近写的一个完整版本，它返回了包装拖缆，所以你可以根据需要使用它。
此外，该方法从随机生成器生成IV，而不是密码摘要。这是最佳实践，例如7z会这样做-请参阅https://crypto.stackexchange.com/questions/61945/is-it-ok-to-transmit-an-iv-as-a-custom-http-header.IV包含在输出的标题中。
用法：
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);
}
}
}
实用程序：
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.
}
}