ECDiffieHellmanCng 類別

定義

public ref class ECDiffieHellmanCng sealed : System::Security::Cryptography::ECDiffieHellman

public sealed class ECDiffieHellmanCng : System.Security.Cryptography.ECDiffieHellman

type ECDiffieHellmanCng = class
    inherit ECDiffieHellman

Public NotInheritable Class ECDiffieHellmanCng
Inherits ECDiffieHellman

繼承

Object

AsymmetricAlgorithm

ECAlgorithm

ECDiffieHellman

ECDiffieHellmanCng

繼承

Object

AsymmetricAlgorithm

ECDiffieHellman

ECDiffieHellmanCng

範例

以下範例展示了如何利用該 ECDiffieHellmanCng 類別建立金鑰交換，以及如何利用該金鑰加密可透過公共通道傳送並由接收方解密的訊息。

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

class Alice
{
    public static byte[] alicePublicKey;

    public static void Main(string[] args)
    {
        using (ECDiffieHellmanCng alice = new ECDiffieHellmanCng())
        {

            alice.KeyDerivationFunction = ECDiffieHellmanKeyDerivationFunction.Hash;
            alice.HashAlgorithm = CngAlgorithm.Sha256;
            alicePublicKey = alice.PublicKey.ToByteArray();
            Bob bob = new Bob();
            CngKey bobKey = CngKey.Import(bob.bobPublicKey, CngKeyBlobFormat.EccPublicBlob);
            byte[] aliceKey = alice.DeriveKeyMaterial(bobKey);
            byte[] encryptedMessage = null;
            byte[] iv = null;
            Send(aliceKey, "Secret message", out encryptedMessage, out iv);
            bob.Receive(encryptedMessage, iv);
        }
    }

    private static void Send(byte[] key, string secretMessage, out byte[] encryptedMessage, out byte[] iv)
    {
        using (Aes aes = new AesCryptoServiceProvider())
        {
            aes.Key = key;
            iv = aes.IV;

            // Encrypt the message
            using (MemoryStream ciphertext = new MemoryStream())
            using (CryptoStream cs = new CryptoStream(ciphertext, aes.CreateEncryptor(), CryptoStreamMode.Write))
            {
                byte[] plaintextMessage = Encoding.UTF8.GetBytes(secretMessage);
                cs.Write(plaintextMessage, 0, plaintextMessage.Length);
                cs.Close();
                encryptedMessage = ciphertext.ToArray();
            }
        }
    }
}
public class Bob
{
    public byte[] bobPublicKey;
    private byte[] bobKey;
    public Bob()
    {
        using (ECDiffieHellmanCng bob = new ECDiffieHellmanCng())
        {

            bob.KeyDerivationFunction = ECDiffieHellmanKeyDerivationFunction.Hash;
            bob.HashAlgorithm = CngAlgorithm.Sha256;
            bobPublicKey = bob.PublicKey.ToByteArray();
            bobKey = bob.DeriveKeyMaterial(CngKey.Import(Alice.alicePublicKey, CngKeyBlobFormat.EccPublicBlob));
        }
    }

    public void Receive(byte[] encryptedMessage, byte[] iv)
    {

        using (Aes aes = new AesCryptoServiceProvider())
        {
            aes.Key = bobKey;
            aes.IV = iv;
            // Decrypt the message
            using (MemoryStream plaintext = new MemoryStream())
            {
                using (CryptoStream cs = new CryptoStream(plaintext, aes.CreateDecryptor(), CryptoStreamMode.Write))
                {
                    cs.Write(encryptedMessage, 0, encryptedMessage.Length);
                    cs.Close();
                    string message = Encoding.UTF8.GetString(plaintext.ToArray());
                    Console.WriteLine(message);
                }
            }
        }
    }
}

Imports System.IO
Imports System.Security.Cryptography
Imports System.Text




Class Alice
    Public Shared alicePublicKey() As Byte


    Public Shared Sub Main(ByVal args() As String)
        Using alice As New ECDiffieHellmanCng()
            alice.KeyDerivationFunction = ECDiffieHellmanKeyDerivationFunction.Hash
            alice.HashAlgorithm = CngAlgorithm.Sha256
            alicePublicKey = alice.PublicKey.ToByteArray()
            Dim bob As New Bob()
            Dim k As CngKey = CngKey.Import(bob.bobPublicKey, CngKeyBlobFormat.EccPublicBlob)
            Dim aliceKey As Byte() = alice.DeriveKeyMaterial(CngKey.Import(bob.bobPublicKey, CngKeyBlobFormat.EccPublicBlob))
            Dim encryptedMessage As Byte() = Nothing
            Dim iv As Byte() = Nothing
            Send(aliceKey, "Secret message", encryptedMessage, iv)
            bob.Receive(encryptedMessage, iv)
        End Using
    End Sub


    Private Shared Sub Send(ByVal key() As Byte, ByVal secretMessage As String, ByRef encryptedMessage() As Byte, ByRef iv() As Byte)
        Using aes As New AesCryptoServiceProvider()
            aes.Key = key
            iv = aes.IV

            ' Encrypt the message
            Using ciphertext As New MemoryStream()
                Using cs As New CryptoStream(ciphertext, aes.CreateEncryptor(), CryptoStreamMode.Write)
                    Dim plaintextMessage As Byte() = Encoding.UTF8.GetBytes(secretMessage)
                    cs.Write(plaintextMessage, 0, plaintextMessage.Length)
                    cs.Close()
                    encryptedMessage = ciphertext.ToArray()
                End Using
            End Using
        End Using

    End Sub
End Class

Public Class Bob
    Public bobPublicKey() As Byte
    Private bobKey() As Byte

    Public Sub New()
        Using bob As New ECDiffieHellmanCng()

            bob.KeyDerivationFunction = ECDiffieHellmanKeyDerivationFunction.Hash
            bob.HashAlgorithm = CngAlgorithm.Sha256
            bobPublicKey = bob.PublicKey.ToByteArray()
            bobKey = bob.DeriveKeyMaterial(CngKey.Import(Alice.alicePublicKey, CngKeyBlobFormat.EccPublicBlob))
        End Using

    End Sub


    Public Sub Receive(ByVal encryptedMessage() As Byte, ByVal iv() As Byte)

        Using aes As New AesCryptoServiceProvider()
                aes.Key = bobKey
                aes.IV = iv
                ' Decrypt the message
            Using plaintext As New MemoryStream()
                Using cs As New CryptoStream(plaintext, aes.CreateDecryptor(), CryptoStreamMode.Write)
                    cs.Write(encryptedMessage, 0, encryptedMessage.Length)
                    cs.Close()
                    Dim message As String = Encoding.UTF8.GetString(plaintext.ToArray())
                    Console.WriteLine(message)
                End Using
            End Using
        End Using
    End Sub
End Class

備註

此 ECDiffieHellmanCng 類別允許雙方即使透過公開通道通訊，也能交換私鑰資料。 雙方可以計算相同的秘密值，這在管理 Diffie-Hellman 類別中稱為 秘密協議 。 秘密協議可用於多種用途，包括作為對稱密鑰。 然而，該 ECDiffieHellmanCng 類別並未直接揭露秘密協議，而是在提供價值前對協議進行後續處理。 此後處理稱為 金鑰推導函數（KDF）;你可以選擇想使用的 KDF，並透過 Diffie-Hellman 物件實例上的一組屬性設定參數。

將秘密協議傳遞給金鑰導出函式後，會產生一個位元組陣列，可用於您的應用程式作為金鑰材料。 產生的金鑰資料位元組數取決於金鑰推導函數;例如，SHA-256 會產生 256 位元的金鑰材料，而 SHA-512 則會產生 512 位元的金鑰材料。 ECDH 金鑰交換的基本流程如下：

1. Alice 和 Bob 建立一對金鑰對，用於 Diffie-Hellman 金鑰交換操作

2. Alice 和 Bob 用他們同意的參數配置 KDF。

3. 愛麗絲把她的公鑰寄給鮑勃。

4. Bob 把他的公開金鑰傳給 Alice。

5. Alice 和 Bob 使用彼此的公鑰來產生秘密協議，並將 KDF 應用於秘密協議以產生密鑰材料。