vbnet 3DES 算法代码 指定键的大小对于此算法无效。

在VB.NET中使用3DES算法进行加密和解密，可以使用TripleDESCryptoServiceProvider类。以下是一个示例代码：

Imports System.Security.Cryptography
Imports System.Text

Public Class TripleDESExample
    Public Shared Sub Main()
        Dim plainText As String = "Hello World!"
        Dim key As String = "123456789012345678901234"
        Dim iv As String = "12345678"
        
        Dim encryptedText As String = Encrypt(plainText, key, iv)
        Console.WriteLine("Encrypted Text: " & encryptedText)
        
        Dim decryptedText As String = Decrypt(encryptedText, key, iv)
        Console.WriteLine("Decrypted Text: " & decryptedText)
    End Sub
    
    Public Shared Function Encrypt(plainText As String, key As String, iv As String) As String
        Dim tripleDes As New TripleDESCryptoServiceProvider()
        tripleDes.Key = Encoding.UTF8.GetBytes(key)
        tripleDes.IV = Encoding.UTF8.GetBytes(iv)
        
        Dim encryptor As ICryptoTransform = tripleDes.CreateEncryptor()
        Dim plainBytes As Byte() = Encoding.UTF8.GetBytes(plainText)
        Dim encryptedBytes As Byte() = encryptor.TransformFinalBlock(plainBytes, 0, plainBytes.Length)
        
        Return Convert.ToBase64String(encryptedBytes)
    End Function
    
    Public Shared Function Decrypt(encryptedText As String, key As String, iv As String) As String
        Dim tripleDes As New TripleDESCryptoServiceProvider()
        tripleDes.Key = Encoding.UTF8.GetBytes(key)
        tripleDes.IV = Encoding.UTF8.GetBytes(iv)
        
        Dim decryptor As ICryptoTransform = tripleDes.CreateDecryptor()
        Dim encryptedBytes As Byte() = Convert.FromBase64String(encryptedText)
        Dim decryptedBytes As Byte() = decryptor.TransformFinalBlock(encryptedBytes, 0, encryptedBytes.Length)
        
        Return Encoding.UTF8.GetString(decryptedBytes)
    End Function
End Class

在上面的示例中，key是一个24字节的字符串，iv是一个8字节的字符串。这两个参数指定了3DES算法的密钥和初始化向量。请确保密钥和向量的长度正确，否则可能导致无效的结果