PowerShell script to convert string to encrypted password and back again

I’ve found it useful to store an encrypted password in a file on disk. However, this is not generally a good idea but at least the password is encrypted to the user/machine. Here is a rough outline of the process:

-- convert to encrypted password from clear text

$password = ConvertTo-SecureString 'SomePassword' -AsPlainText –Force

-- write to file as user/machine encrypted string which cannot be unencrypted by any other user on any other machine

$password|convertFrom-SecureString|set-content "c:\temp\cred.txt"

$password

 

To make the file really useable, preface the password with the username and query for the username:

— query for user name from file

$username = "UserName";

-- convert password to a secure string that can be sent through to Windows for authentication

$password = Get-Content "c:\temp\cred.txt" | Select-String $Username | foreach{$_ -replace $Username, ""} | foreach{$_ -replace " ",""} | ConvertTo-SecureString;

 

Finally, you can go a step further and crack open the password:

-- convert from encrypted password to clear text

$Ptr = [System.Runtime.InteropServices.Marshal]::SecureStringToCoTaskMemUnicode($password);

$password = [System.Runtime.InteropServices.Marshal]::PtrToStringUni($Ptr);[System.Runtime.InteropServices.Marshal]::ZeroFreeCoTaskMemUnicode($Ptr);

$password