HashAlgorithm.ComputeHash Metoda

Definice

Obor názvů:

System.Security.Cryptography

Sestavení:

System.Security.Cryptography.dll

Vypočítá hodnotu hash pro vstupní data.

Přetížení

ComputeHash(Byte[])	Vypočítá hodnotu hash zadaného pole bajtů.
ComputeHash(Stream)	Vypočítá hodnotu hash pro zadaný Stream objekt.
ComputeHash(Byte[], Int32, Int32)	Vypočítá hodnotu hash pro zadanou oblast zadaného pole bajtů.

ComputeHash(Byte[])

Zdroj:

HashAlgorithm.cs

Vypočítá hodnotu hash zadaného pole bajtů.

public:
 cli::array <System::Byte> ^ ComputeHash(cli::array <System::Byte> ^ buffer);

public byte[] ComputeHash (byte[] buffer);

member this.ComputeHash : byte[] -> byte[]

Public Function ComputeHash (buffer As Byte()) As Byte()

Parametry

buffer

Byte[]

Vstup pro výpočet hashového kódu.

Návraty

Byte[]

Vypočítaný kód hash.

Výjimky

ArgumentNullException

buffer je null.

ObjectDisposedException

Objekt již byl odstraněn.

Příklady

Následující příklad vypočítá SHA256 hodnotu hash řetězce a vrátí hodnotu hash jako řetězec v šestnáctkovém formátu 64 znaků. Řetězec hash vytvořený tímto příkladem kódu je kompatibilní s libovolnou funkcí hash SHA256 (na libovolné platformě), která vytvoří 64znakový šestnáctkový hashovací řetězec.

using System;
using System.Security.Cryptography;
using System.Text;

public class Program
{
    public static void Main()
    {
        string source = "Hello World!";
        using (SHA256 sha256Hash = SHA256.Create())
        {
            string hash = GetHash(sha256Hash, source);

            Console.WriteLine($"The SHA256 hash of {source} is: {hash}.");

            Console.WriteLine("Verifying the hash...");

            if (VerifyHash(sha256Hash, source, hash))
            {
                Console.WriteLine("The hashes are the same.");
            }
            else
            {
                Console.WriteLine("The hashes are not same.");
            }
        }
    }

    private static string GetHash(HashAlgorithm hashAlgorithm, string input)
    {

        // Convert the input string to a byte array and compute the hash.
        byte[] data = hashAlgorithm.ComputeHash(Encoding.UTF8.GetBytes(input));

        // Create a new Stringbuilder to collect the bytes
        // and create a string.
        var sBuilder = new StringBuilder();

        // Loop through each byte of the hashed data
        // and format each one as a hexadecimal string.
        for (int i = 0; i < data.Length; i++)
        {
            sBuilder.Append(data[i].ToString("x2"));
        }

        // Return the hexadecimal string.
        return sBuilder.ToString();
    }

    // Verify a hash against a string.
    private static bool VerifyHash(HashAlgorithm hashAlgorithm, string input, string hash)
    {
        // Hash the input.
        var hashOfInput = GetHash(hashAlgorithm, input);

        // Create a StringComparer an compare the hashes.
        StringComparer comparer = StringComparer.OrdinalIgnoreCase;

        return comparer.Compare(hashOfInput, hash) == 0;
    }
}
// The example displays the following output:
//    The SHA256 hash of Hello World! is: 7f83b1657ff1fc53b92dc18148a1d65dfc2d4b1fa3d677284addd200126d9069.
//    Verifying the hash...
//    The hashes are the same.

Imports System.Security.Cryptography
Imports System.Text

Public Module Program
    Public Sub Main()
        Dim source As String = "Hello World!"
        Using sha256Hash As SHA256 = SHA256.Create()

            Dim hash As String = GetHash(sha256Hash, source)

            Console.WriteLine($"The SHA256 hash of {source} is: {hash}.")

            Console.WriteLine("Verifying the hash...")

            If VerifyHash(sha256Hash, source, hash) Then
                Console.WriteLine("The hashes are the same.")
            Else
                Console.WriteLine("The hashes are not same.")
            End If
        End Using
    End Sub 

    Private Function GetHash(ByVal hashAlgorithm As HashAlgorithm, ByVal input As String) As String

        ' Convert the input string to a byte array and compute the hash.
        Dim data As Byte() = hashAlgorithm.ComputeHash(Encoding.UTF8.GetBytes(input))

        ' Create a new Stringbuilder to collect the bytes
        ' and create a string.
        Dim sBuilder As New StringBuilder()

        ' Loop through each byte of the hashed data 
        ' and format each one as a hexadecimal string.
        For i As Integer = 0 To data.Length - 1
            sBuilder.Append(data(i).ToString("x2"))
        Next

        ' Return the hexadecimal string.
        Return sBuilder.ToString()
    End Function

    ' Verify a hash against a string.
    Private Function VerifyHash(hashAlgorithm As HashAlgorithm, input As String, hash As String) As Boolean
        ' Hash the input.
        Dim hashOfInput As String = GetHash(hashAlgorithm, input)

        ' Create a StringComparer an compare the hashes.
        Dim comparer As StringComparer = StringComparer.OrdinalIgnoreCase

        Return comparer.Compare(hashOfInput, hash) = 0
    End Function
End Module
' The example displays the following output:
'    The SHA256 hash of Hello World! is: 7f83b1657ff1fc53b92dc18148a1d65dfc2d4b1fa3d677284addd200126d9069.
'    Verifying the hash...
'    The hashes are the same.

ComputeHash(Stream)

Zdroj:

HashAlgorithm.cs

Vypočítá hodnotu hash pro zadaný Stream objekt.

public:
 cli::array <System::Byte> ^ ComputeHash(System::IO::Stream ^ inputStream);

public byte[] ComputeHash (System.IO.Stream inputStream);

member this.ComputeHash : System.IO.Stream -> byte[]

Public Function ComputeHash (inputStream As Stream) As Byte()

Parametry

inputStream

Stream

Vstup pro výpočet hashového kódu.

Návraty

Byte[]

Vypočítaný kód hash.

Výjimky

ObjectDisposedException

Objekt již byl odstraněn.

Příklady

Následující příklad vypočítá SHA256 hodnotu hash pro všechny soubory v adresáři.

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

ComputeHash(Byte[], Int32, Int32)

Zdroj:

HashAlgorithm.cs

Vypočítá hodnotu hash pro zadanou oblast zadaného pole bajtů.

public:
 cli::array <System::Byte> ^ ComputeHash(cli::array <System::Byte> ^ buffer, int offset, int count);

public byte[] ComputeHash (byte[] buffer, int offset, int count);

member this.ComputeHash : byte[] * int * int -> byte[]

Public Function ComputeHash (buffer As Byte(), offset As Integer, count As Integer) As Byte()

Parametry

buffer

Byte[]

Vstup pro výpočet hashového kódu.

offset

Int32

Posun pole bajtů, ze kterého chcete začít používat data.

count

Int32

Počet bajtů v poli, které se mají použít jako data.

Návraty

Byte[]

Vypočítaný kód hash.

Výjimky

ArgumentException

count je neplatná hodnota.

-nebo-

buffer délka je neplatná.

ArgumentNullException

buffer je null.

ArgumentOutOfRangeException

offset je mimo rozsah. Tento parametr vyžaduje nezáporné číslo.

ObjectDisposedException

Objekt již byl odstraněn.