Unprotect-AESMessage.ps1
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Function Unprotect-AESMessage { <# .SYNOPSIS Decrypt AES256 message .PARAMETER Message Message to decrypt. .PARAMETER Password Password to decrypt message. .PARAMETER Salt Salt to decrypt message. Encrypt and decrypt must use the same salt. .PARAMETER HashAlgorithm HashAlgorithm used for key to encrypt message. .EXAMPLE $Result = "WdwAzBT1QZ5njJAJQ8yM6xKBP+iuq87MJP70AuIyD/A=" Unprotect-AESMessage -Message $Result -Password "A Secret Password" -Salt @(1,2,3,4,5,6,7,9,10,11,252,253,254) .NOTES Michal Gajda #> [CmdletBinding()] Param( [Parameter(Mandatory=$true)] [String]$Message, [Parameter(Mandatory=$true)] [String]$Password, [Parameter(Mandatory=$false)] [Byte[]]$Salt, [Parameter()] [ValidateSet("MD5","SHA1","SHA256","SHA384","SHA512")] [String]$HashAlgorithm = "SHA512" ) $MessageBytes = [System.Convert]::FromBase64String($Message) $PasswordBytes = [System.Text.Encoding]::ASCII.GetBytes($Password) # Salt must have at least 8 Bytes! [Byte[]]$SaltBytes = @(21,251,43,109,115,57,88,24,249,222,68,134,79,196,197,169) if($Salt.Count -ge 8) { $SaltBytes = $Salt } [System.IO.MemoryStream] $MemoryStream = New-Object System.IO.MemoryStream [System.Security.Cryptography.Aes]$AES = [System.Security.Cryptography.Aes]::Create() $AES.KeySize = 256 $AES.BlockSize = 128 [System.Security.Cryptography.Rfc2898DeriveBytes] $Key = New-Object System.Security.Cryptography.Rfc2898DeriveBytes($PasswordBytes, $SaltBytes, 1000, [System.Security.Cryptography.HashAlgorithmName]::$HashAlgorithm) $AES.Key = $Key.GetBytes($AES.KeySize / 8) $AES.IV = $Key.GetBytes($AES.BlockSize / 8) $AES.Mode = [System.Security.Cryptography.CipherMode]::CBC $CryptoStream = New-Object System.Security.Cryptography.CryptoStream($MemoryStream, $AES.CreateDecryptor(), [System.Security.Cryptography.CryptoStreamMode]::Write) try { $CryptoStream.Write($MessageBytes, 0, $MessageBytes.Length) $CryptoStream.Close() } catch [Exception] { $Result = "Error occured while decoding string. Password, Salt or HashAlgorithm incorrect?" return $Result } $DecryptedBytes = $MemoryStream.ToArray() $Result = [System.Text.Encoding]::UTF8.GetString($DecryptedBytes) return $Result } |