融资平台公司定义宁波seo排名方案优化公司
[作者:张赐荣]
对称加密是一种加密技术，它使用相同的密钥来加密和解密数据。换句话说，加密者和解密者需要共享同一个密钥，才能进行通信。
对称加密的优点是速度快，效率高，适合大量数据的加密。对称加密的缺点是密钥的管理和分发比较困难，如果密钥泄露或被破解，那么加密的数据就会失去保密性。
AES是一种高级加密标准，它是一种对称加密算法，也就是说，它使用相同的密钥来加密和解密数据。AES是美国国家标准技术研究所（NIST）在2001年选定的一种加密算法，用于替代旧的DES算法。AES支持三种不同的密钥长度：128位，192位和256位。AES的安全性很高，目前还没有找到有效的攻击方法。
下面两个函数使用AES，加/解密文件。
需要引用 "System.Security.Cryptography" 命名空间。
// 加密文件
public static async Task<bool> EncryptFileAsync (string inputFilePath, string outputFilePath, string key, Action<double> progressCallback = default, CancellationToken cancellationToken = default)
{
HashSet<IDisposable> disposables = new HashSet<IDisposable>();
try
{
var md5 = MD5.Create();
disposables.Add(md5);
var md5Key = md5.ComputeHash(Encoding.Unicode.GetBytes(key));
var aes = Aes.Create();
disposables.Add(aes);
aes.Key = md5Key;
var aesEncryptor = aes.CreateEncryptor();
disposables.Add(aesEncryptor);
var inputStream = File.OpenRead(inputFilePath);
disposables.Add(inputStream);
var outputStream = File.OpenWrite(outputFilePath);
disposables.Add(outputStream);
aes.GenerateIV();
await outputStream.WriteAsync(aes.IV,0,aes.IV.Length,cancellationToken);
var encryptoWriterStream = new CryptoStream(outputStream,aesEncryptor,CryptoStreamMode.Write);
disposables.Add(encryptoWriterStream);
var buffer = new byte[65536];
var readLength = -1;
while ((readLength = await inputStream.ReadAsync(buffer,0,buffer.Length,cancellationToken)) > 0)
{
await encryptoWriterStream.WriteAsync(buffer,0,readLength,cancellationToken);
progressCallback?.Invoke(Math.Round(((double)(inputStream.Position +1 - aes.IV.Length) / inputStream.Length) * 100,2));
}
if (!encryptoWriterStream.HasFlushedFinalBlock)
{
encryptoWriterStream.FlushFinalBlock();
progressCallback?.Invoke(100.00);
}
return (true);
}
catch (Exception ex)
{
return (false);
}
finally
{
foreach (var disposableObject in disposables)
{
try
{
disposableObject.Dispose();
}
catch (Exception ex)
{
continue;
}
}
}
}
// 解密文件
public static async Task<bool> DecryptFileAsync (string inputFilePath, string outputFilePath, string key, Action<double> progressCallback = default, CancellationToken cancellationToken = default)
{
HashSet<IDisposable> disposables = new HashSet<IDisposable>();
try
{
var md5 = MD5.Create();
disposables.Add(md5);
var md5Key = md5.ComputeHash(Encoding.Unicode.GetBytes(key));
var inputStream = File.OpenRead(inputFilePath);
disposables.Add(inputStream);
byte[] iv = new byte[16];
await inputStream. ReadAsync(iv,0,iv.Length,cancellationToken);
var aes = Aes.Create();
disposables.Add(aes);
aes.Key = md5Key;
aes.IV = iv;
var aesDecryptor = aes.CreateDecryptor();
disposables.Add(aesDecryptor);
var DecryptorReaderStream = new CryptoStream(inputStream,aesDecryptor,CryptoStreamMode.Read);
disposables.Add(DecryptorReaderStream);
var outputStream = File.OpenWrite(outputFilePath);
disposables.Add(outputStream);
var buffer = new byte[65536];
var readLength = -1;
while ((readLength = await DecryptorReaderStream.ReadAsync(buffer,0,buffer.Length,cancellationToken)) > 0)
{
await outputStream.WriteAsync(buffer,0,readLength,cancellationToken);
progressCallback?.Invoke(Math.Round(((double)(inputStream.Position + 1) / inputStream.Length) * 100, 2));
}
if (!DecryptorReaderStream.HasFlushedFinalBlock)
{
DecryptorReaderStream.FlushFinalBlock();
progressCallback?.Invoke(100.00);
}
return (true);
}
catch (Exception ex)
{
return (false);
}
finally
{
foreach (var disposableObject in disposables)
{
try
{
disposableObject.Dispose();
}
catch (Exception ex)
{
continue;
}
}
}
}