SHA256 類別
定義
重要
部分資訊涉及發行前產品，在發行之前可能會有大幅修改。 Microsoft 對此處提供的資訊，不做任何明確或隱含的瑕疵擔保。
計算輸入資料的 SHA256 雜湊。
public ref class SHA256 abstract : System::Security::Cryptography::HashAlgorithmpublic abstract class SHA256 : System.Security.Cryptography.HashAlgorithm[System.Runtime.InteropServices.ComVisible(true)]
public abstract class SHA256 : System.Security.Cryptography.HashAlgorithmtype SHA256 = class
inherit HashAlgorithm[<System.Runtime.InteropServices.ComVisible(true)>]
type SHA256 = class
inherit HashAlgorithmPublic MustInherit Class SHA256
Inherits HashAlgorithm- 繼承
- 衍生
- 屬性
範例
下列範例會計算目錄中所有檔案的SHA-256哈希。
using namespace System;
using namespace System::IO;
using namespace System::Security::Cryptography;
// Print the byte array in a readable format.
void PrintByteArray( array<Byte>^array )
{
int i;
for ( i = 0; i < array->Length; i++ )
{
Console::Write( String::Format( "{0:X2}", array[ i ] ) );
if ( (i % 4) == 3 )
Console::Write( " " );
}
Console::WriteLine();
}
int main()
{
array<String^>^args = Environment::GetCommandLineArgs();
if ( args->Length < 2 )
{
Console::WriteLine( "Usage: hashdir <directory>" );
return 0;
}
try
{
// Create a DirectoryInfo object representing the specified directory.
DirectoryInfo^ dir = gcnew DirectoryInfo( args[ 1 ] );
// Get the FileInfo objects for every file in the directory.
array<FileInfo^>^files = dir->GetFiles();
// Initialize a SHA256 hash object.
SHA256 ^ mySHA256 = SHA256Managed::Create();
array<Byte>^hashValue;
// Compute and print the hash values for each file in directory.
System::Collections::IEnumerator^ myEnum = files->GetEnumerator();
while ( myEnum->MoveNext() )
{
FileInfo^ fInfo = safe_cast<FileInfo^>(myEnum->Current);
// Create a fileStream for the file.
FileStream^ fileStream = fInfo->Open( FileMode::Open );
// Compute the hash of the fileStream.
hashValue = mySHA256->ComputeHash( fileStream );
// Write the name of the file to the Console.
Console::Write( "{0}: ", fInfo->Name );
// Write the hash value to the Console.
PrintByteArray( hashValue );
// Close the file.
fileStream->Close();
}
return 0;
}
catch ( DirectoryNotFoundException^ )
{
Console::WriteLine( "Error: The directory specified could not be found." );
}
catch ( IOException^ )
{
Console::WriteLine( "Error: A file in the directory could not be accessed." );
}
}
using System;
using System.IO;
using System.Security.Cryptography;
public class HashDirectory
{
public static void Main(string[] args)
{
if (args.Length < 1)
{
Console.WriteLine("No directory selected.");
return;
}
string directory = args[0];
if (Directory.Exists(directory))
{
// Create a DirectoryInfo object representing the specified directory.
var dir = new DirectoryInfo(directory);
// Get the FileInfo objects for every file in the directory.
FileInfo[] files = dir.GetFiles();
// Initialize a SHA256 hash object.
using (SHA256 mySHA256 = SHA256.Create())
{
// Compute and print the hash values for each file in directory.
foreach (FileInfo fInfo in files)
{
using (FileStream fileStream = fInfo.Open(FileMode.Open))
{
try
{
// Create a fileStream for the file.
// Be sure it's positioned to the beginning of the stream.
fileStream.Position = 0;
// Compute the hash of the fileStream.
byte[] hashValue = mySHA256.ComputeHash(fileStream);
// Write the name and hash value of the file to the console.
Console.Write($"{fInfo.Name}: ");
PrintByteArray(hashValue);
}
catch (IOException e)
{
Console.WriteLine($"I/O Exception: {e.Message}");
}
catch (UnauthorizedAccessException e)
{
Console.WriteLine($"Access Exception: {e.Message}");
}
}
}
}
}
else
{
Console.WriteLine("The directory specified could not be found.");
}
}
// Display the byte array in a readable format.
public static void PrintByteArray(byte[] array)
{
for (int i = 0; i < array.Length; i++)
{
Console.Write($"{array[i]:X2}");
if ((i % 4) == 3) Console.Write(" ");
}
Console.WriteLine();
}
}
Imports System.IO
Imports System.Security.Cryptography
Public Module HashDirectory
Public Sub Main(ByVal args() As String)
If args.Length < 1 Then
Console.WriteLine("No directory selected")
Return
End If
Dim targetDirectory As String = args(0)
If Directory.Exists(targetDirectory) Then
' Create a DirectoryInfo object representing the specified directory.
Dim dir As New DirectoryInfo(targetDirectory)
' Get the FileInfo objects for every file in the directory.
Dim files As FileInfo() = dir.GetFiles()
' Initialize a SHA256 hash object.
Using mySHA256 As SHA256 = SHA256.Create()
' Compute and print the hash values for each file in directory.
For Each fInfo As FileInfo In files
Try
' Create a fileStream for the file.
Dim fileStream = fInfo.Open(FileMode.Open)
' Be sure it's positioned to the beginning of the stream.
fileStream.Position = 0
' Compute the hash of the fileStream.
Dim hashValue() As Byte = mySHA256.ComputeHash(fileStream)
' Write the name of the file to the Console.
Console.Write(fInfo.Name + ": ")
' Write the hash value to the Console.
PrintByteArray(hashValue)
' Close the file.
fileStream.Close()
Catch e As IOException
Console.WriteLine($"I/O Exception: {e.Message}")
Catch e As UnauthorizedAccessException
Console.WriteLine($"Access Exception: {e.Message}")
End Try
Next
End Using
Else
Console.WriteLine("The directory specified could not be found.")
End If
End Sub
' Print the byte array in a readable format.
Public Sub PrintByteArray(array() As Byte)
For i As Integer = 0 To array.Length - 1
Console.Write($"{array(i):X2}")
If i Mod 4 = 3 Then
Console.Write(" ")
End If
Next
Console.WriteLine()
End Sub
End Module
備註
哈希是用來做為代表大量數據之固定大小的唯一值。 如果對應數據也相符，則兩組數據的哈希應該相符。 對數據的小型變更會導致哈希中發生大量無法預測的變更。
演算法的 SHA256 哈希大小為256位。
這是 abstract 類別。
建構函式
| SHA256() |
初始化 SHA256 的新執行個體。 |
欄位
| HashSizeInBits |
SHA256 演算法所產生的哈希大小，以位為單位。 |
| HashSizeInBytes |
SHA256 演算法所產生的哈希大小，以位元組為單位。 |
| HashSizeValue |
代表計算出來之雜湊碼的大小，以位元為單位。 (繼承來源 HashAlgorithm) |
| HashValue |
表示計算出來的雜湊碼的值。 (繼承來源 HashAlgorithm) |
| State |
表示雜湊計算的狀態。 (繼承來源 HashAlgorithm) |
屬性
| CanReuseTransform |
取得值，表示目前的轉換是否可重複使用。 (繼承來源 HashAlgorithm) |
| CanTransformMultipleBlocks |
在衍生類別中覆寫時，取得值以指出是否有多個區塊可被轉換。 (繼承來源 HashAlgorithm) |
| Hash |
取得計算出來之雜湊碼的值。 (繼承來源 HashAlgorithm) |
| HashSize |
取得計算出來之雜湊碼的大小，以位元為單位。 (繼承來源 HashAlgorithm) |
| InputBlockSize |
在衍生類別中覆寫時，取得輸入區塊的大小。 (繼承來源 HashAlgorithm) |
| OutputBlockSize |
在衍生類別中覆寫時，取得輸出區塊的大小。 (繼承來源 HashAlgorithm) |
方法
明確介面實作
| IDisposable.Dispose() |
釋放 HashAlgorithm 所使用的 Unmanaged 資源，並選擇性地釋放 Managed 資源。 (繼承來源 HashAlgorithm) |
