How to Decrypt Password Files that Have Been Encrypted with a Key

Decrypt-SecurePasswords.ps1

$keyPath  = 'path.key'  
$passPath = 'path.txt'
$account  = 'username'

$key  = Get-Content -Path $keyPath
$pass = Get-Content -Path $passPath | ConvertTo-SecureString -Key $key

# POWERSHELL 5.1, 6
$credentials = New-Object -TypeName System.Management.Automation.PSCredential($account,$pass)
$clearPass   = $credentials.GetNetworkCredential().Password

# POWERSHELL 7
$clearPass = ConvertFrom-SecureString -SecureString $pass -AsPlainText

Overview

Examples on how to derive a cleartext password from an encrypted string when you have access to the key that was used to encrypt it.

Resources & Documentation

• Encrypting Passwords in a PowerShell Script
• ConvertFrom-SecureString (PS7)
• Using the PowerShell Get-Credential Cmdlet and all things credentials
• PSCredential Class