ConvertFrom-SecureString is a cmdlet in Windows PowerShell used to convert a secure string into an encrypted standard string representation. This is particularly useful when you need to store or transmit sensitive information, such as passwords, in a secure manner. The resulting string can be stored in a file or passed over a network, and it can only be decrypted by a user with the appropriate permissions and access to the encryption key.

Examples:

1. Basic Usage of ConvertFrom-SecureString

   To convert a secure string to an encrypted standard string, you first need to create a secure string. This can be done using the ConvertTo-SecureString cmdlet. Here’s a step-by-step example:

   # Create a secure string from a plain text password
   $securePassword = ConvertTo-SecureString "P@ssw0rd!" -AsPlainText -Force
   
   # Convert the secure string to an encrypted standard string
   $encryptedString = $securePassword | ConvertFrom-SecureString
   
   # Display the encrypted string
   Write-Output $encryptedString

   In this example, ConvertTo-SecureString is used to create a secure string from a plain text password. The ConvertFrom-SecureString cmdlet then converts this secure string into an encrypted string that can be safely stored or transmitted.

2. Storing the Encrypted String in a File

   You can store the encrypted string in a file for later use. Here’s how you can do it:

   # Convert the secure string to an encrypted standard string
   $encryptedString = $securePassword | ConvertFrom-SecureString
   
   # Save the encrypted string to a file
   $filePath = "C:\secure\encryptedPassword.txt"
   Set-Content -Path $filePath -Value $encryptedString

   This script saves the encrypted string to a file located at C:\secure\encryptedPassword.txt. Ensure that the directory is secure and accessible only to authorized users.

3. Decrypting the Encrypted String

   To use the encrypted string, you need to convert it back to a secure string and then to plain text (if necessary). Here’s how you can decrypt the string:

   # Read the encrypted string from the file
   $encryptedString = Get-Content -Path $filePath
   
   # Convert the encrypted string back to a secure string
   $securePassword = ConvertTo-SecureString -String $encryptedString
   
   # Convert the secure string back to plain text (only if necessary and secure to do so)
   $plainPassword = [System.Runtime.InteropServices.Marshal]::PtrToStringAuto([System.Runtime.InteropServices.Marshal]::SecureStringToBSTR($securePassword))
   
   # Display the plain text password
   Write-Output $plainPassword

   Note: Converting a secure string back to plain text should be done with caution and only when absolutely necessary, as it exposes the sensitive information.