MachineKey生成

 https://support.microsoft.com/zh-cn/help/2915218/resolving-view-state-message-authentication-code-mac-errors#appendixa

安全警告：
只需单击一下按钮，您就可以通过许多网站生成 <machineKey> 元素。切勿使用通过这些网站获得的 <machineKey> 元素。这些密钥是否安全创建或者是否记录到秘密数据库，都无从而知。必须使用您自己创建的 <machineKey> 配置元素。

打开PowerShell然后粘贴以下代码回车

# 生成一个可复制并粘贴到 Web.config 文件中的 <machineKey> 元素。
function Generate-MachineKey {
[CmdletBinding()]
param (
[ValidateSet("AES", "DES", "3DES")]
[string]$decryptionAlgorithm = 'AES',
[ValidateSet("MD5", "SHA1", "HMACSHA256", "HMACSHA384", "HMACSHA512")]
[string]$validationAlgorithm = 'HMACSHA256'
  )
process {
function BinaryToHex {
[CmdLetBinding()]
param($bytes)
process {
$builder = new-object System.Text.StringBuilder
foreach ($b in $bytes) {
$builder = $builder.AppendFormat([System.Globalization.CultureInfo]::InvariantCulture, "{0:X2}", $b)
            }
$builder
        }
    }
switch ($decryptionAlgorithm) {
"AES" { $decryptionObject = new-object System.Security.Cryptography.AesCryptoServiceProvider }
"DES" { $decryptionObject = new-object System.Security.Cryptography.DESCryptoServiceProvider }
"3DES" { $decryptionObject = new-object System.Security.Cryptography.TripleDESCryptoServiceProvider }
    }
$decryptionObject.GenerateKey()
$decryptionKey = BinaryToHex($decryptionObject.Key)
$decryptionObject.Dispose()
switch ($validationAlgorithm) {
"MD5" { $validationObject = new-object System.Security.Cryptography.HMACMD5 }
"SHA1" { $validationObject = new-object System.Security.Cryptography.HMACSHA1 }
"HMACSHA256" { $validationObject = new-object System.Security.Cryptography.HMACSHA256 }
"HMACSHA385" { $validationObject = new-object System.Security.Cryptography.HMACSHA384 }
"HMACSHA512" { $validationObject = new-object System.Security.Cryptography.HMACSHA512 }
    }
$validationKey = BinaryToHex($validationObject.Key)
$validationObject.Dispose()
[string]::Format([System.Globalization.CultureInfo]::InvariantCulture,
"<machineKey decryption=`"{0}`" decryptionKey=`"{1}`" validation=`"{2}`" validationKey=`"{3}`" />",
$decryptionAlgorithm.ToUpperInvariant(), $decryptionKey,
$validationAlgorithm.ToUpperInvariant(), $validationKey)
  }
}

对于 ASP.NET 4.0 应用程序，您只需调用 Generate-MachineKey（不带参数），就能生成 <machineKey> 元素，如下所示：

PS> Generate-MachineKey
<machineKey decryption="AES" decryptionKey="..." validation="HMACSHA256" validationKey="..."/>

ASP.NET 2.0 和 3.5 应用程序不支持 HMACSHA256。您可以改为指定 SHA1 来生成一个兼容的 <machineKey> 元素，如下所示：

PS> Generate-MachineKey -validation sha1
<machineKey decryption="AES" decryptionKey="..." validation="SHA1" validationKey="..."/>