从C中长度未知的流计算哈希#

开始:

HashAlgorithm hasher = ..;
hasher.Initialize();

byte[] buffer = ..;
int bytesReceived = ..;
hasher.TransformBlock(buffer, 0, bytesReceived, null, 0);

要完成并检索哈希:

hasher.TransformFinalBlock(new byte[0], 0, 0);
byte[] hash = hasher.Hash;

此模式适用于从 HashAlgorithm MD5CryptoServiceProvider SHA1Managed .

哈希算法 ComputeHash 这需要一个 Stream 对象;但是,此方法将阻止线程,直到流被使用为止。使用 TransformBlock 这种方法允许在数据到达时计算“异步哈希”,而不使用线程。

这个 System.Security.Cryptography.MD5 ComputeHash 方法 byte[] 或 Stream . 退房 the documentation .

ComputeHash() :

private static string CalculateMd5(string filePathName) {
   using (var stream = File.OpenRead(filePathName))
   using (var md5 = MD5.Create()) {
      var hash = md5.ComputeHash(stream);
      var base64String = Convert.ToBase64String(hash);
      return base64String;
   }
}

因为流和MD5都实现了idisposable,所以您需要使用 using(...){...}

代码示例中的方法返回与Azure Blob存储中的MD5校验和相同的字符串。

这似乎是一个完美的用例 CryptoStream ( docs ).

标准接口 用于处理未知长度的数据库结果流,这些结果需要gzip压缩,然后与压缩文件的哈希一起通过网络传输。插入 标准接口

基本方法如下所示:

var hasher = MD5.Create();
using (FileStream outFile = File.Create(filePath))
using (CryptoStream crypto = new CryptoStream(outFile, hasher, CryptoStreamMode.Write))
using (GZipStream compress = new GZipStream(crypto, CompressionMode.Compress))
using (StreamWriter writer = new StreamWriter(compress))
{
    foreach (string line in GetLines())
        writer.WriteLine(line);
}
// at this point the streams are closed so the hash is ready
string hash = BitConverter.ToString(hasher.Hash).Replace("-", "").ToLowerInvariant();

C#.NET核心中有两种可能性:

private static System.Security.Cryptography.HashAlgorithm GetHashAlgorithm(System.Security.Cryptography.HashAlgorithmName hashAlgorithmName)
{
    if (hashAlgorithmName == System.Security.Cryptography.HashAlgorithmName.MD5)
        return (System.Security.Cryptography.HashAlgorithm) System.Security.Cryptography.MD5.Create();
    if (hashAlgorithmName == System.Security.Cryptography.HashAlgorithmName.SHA1)
        return (System.Security.Cryptography.HashAlgorithm) System.Security.Cryptography.SHA1.Create();
    if (hashAlgorithmName == System.Security.Cryptography.HashAlgorithmName.SHA256)
        return (System.Security.Cryptography.HashAlgorithm) System.Security.Cryptography.SHA256.Create();
    if (hashAlgorithmName == System.Security.Cryptography.HashAlgorithmName.SHA384)
        return (System.Security.Cryptography.HashAlgorithm) System.Security.Cryptography.SHA384.Create();
    if (hashAlgorithmName == System.Security.Cryptography.HashAlgorithmName.SHA512)
        return (System.Security.Cryptography.HashAlgorithm) System.Security.Cryptography.SHA512.Create();

    throw new System.Security.Cryptography.CryptographicException($"Unknown hash algorithm \"{hashAlgorithmName.Name}\".");
}


protected override byte[] HashData(System.IO.Stream data,
    System.Security.Cryptography.HashAlgorithmName hashAlgorithm)
{
    using (System.Security.Cryptography.HashAlgorithm hashAlgorithm1 = 
    GetHashAlgorithm(hashAlgorithm))
    return hashAlgorithm1.ComputeHash(data);
}

或使用BouncyCastle:

private static Org.BouncyCastle.Crypto.IDigest GetBouncyAlgorithm(
    System.Security.Cryptography.HashAlgorithmName hashAlgorithmName)
{
    if (hashAlgorithmName == System.Security.Cryptography.HashAlgorithmName.MD5)
        return new Org.BouncyCastle.Crypto.Digests.MD5Digest();
    if (hashAlgorithmName == System.Security.Cryptography.HashAlgorithmName.SHA1)
        return new Org.BouncyCastle.Crypto.Digests.Sha1Digest();
    if (hashAlgorithmName == System.Security.Cryptography.HashAlgorithmName.SHA256)
        return new Org.BouncyCastle.Crypto.Digests.Sha256Digest();
    if (hashAlgorithmName == System.Security.Cryptography.HashAlgorithmName.SHA384)
        return new Org.BouncyCastle.Crypto.Digests.Sha384Digest();
    if (hashAlgorithmName == System.Security.Cryptography.HashAlgorithmName.SHA512)
        return new Org.BouncyCastle.Crypto.Digests.Sha512Digest();

    throw new System.Security.Cryptography.CryptographicException(
        $"Unknown hash algorithm \"{hashAlgorithmName.Name}\"."
    );
} // End Function GetBouncyAlgorithm  



protected override byte[] HashData(System.IO.Stream data,
    System.Security.Cryptography.HashAlgorithmName hashAlgorithm)
{
    Org.BouncyCastle.Crypto.IDigest digest = GetBouncyAlgorithm(hashAlgorithm);

    byte[] buffer = new byte[4096];
    int cbSize;
    while ((cbSize = data.Read(buffer, 0, buffer.Length)) > 0)
        digest.BlockUpdate(buffer, 0, cbSize);

    byte[] hash = new byte[digest.GetDigestSize()];
    digest.DoFinal(hash, 0);
    return hash;
}