SHA256 类
定义
重要
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计算输入数据的 SHA256 哈希值。
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- 继承
- 派生
- 属性
示例
以下示例计算目录中所有文件的 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
注解
哈希用作表示大量数据的固定大小的唯一值。 当并且仅当相应数据也匹配时，两组数据的哈希应匹配。 对数据的小更改会导致哈希中出现大量不可预知的更改。
算法的 SHA256 哈希大小为 256 位。
这是一个抽象类。
构造函数
| SHA256() |
初始化 SHA256 的新实例。 |
字段
| HashSizeInBits |
SHA256 算法生成的哈希大小（以位为单位）。 |
| HashSizeInBytes |
SHA256 算法生成的哈希大小（以字节为单位）。 |
| HashSizeValue |
表示计算所得的哈希代码的大小（以位为单位）。 (继承自 HashAlgorithm) |
| HashValue |
表示计算所得的哈希代码的值。 (继承自 HashAlgorithm) |
| State |
表示哈希计算的状态。 (继承自 HashAlgorithm) |
属性
| CanReuseTransform |
获取一个值，该值指示是否可重复使用当前转换。 (继承自 HashAlgorithm) |
| CanTransformMultipleBlocks |
当在派生类中重写时，获取一个值，该值指示是否可以转换多个块。 (继承自 HashAlgorithm) |
| Hash |
获取计算所得的哈希代码的值。 (继承自 HashAlgorithm) |
| HashSize |
获取计算所得的哈希代码的大小（以位为单位）。 (继承自 HashAlgorithm) |
| InputBlockSize |
当在派生类中重写时，获取输入块的大小。 (继承自 HashAlgorithm) |
| OutputBlockSize |
当在派生类中重写时，获取输出块的大小。 (继承自 HashAlgorithm) |
方法
显式接口实现
| IDisposable.Dispose() |
释放由 HashAlgorithm 占用的非托管资源，还可以另外再释放托管资源。 (继承自 HashAlgorithm) |
