Encryption & Decryption using native .NET classes

Encrypt-Decrypt-WithDotNet.ps1

## Encryption & Decryption using native .NET functions

## This is Symetrical encryption. Which means the same key is used to both encrypt and decrypt.

## The encryption method is based on AES 256bit.

## The major difference between this option and the ConvertFrom/To-SecureString functions
## is that this way produces much smaller encrypted files.
## I have not compared the 2 options in regards to performance though, as-in which one is faster.


function Encrypt-String {
[cmdletbinding()]
param (
    [ValidateLength(32,32)]
    [string]$Key,

    [string]$InputString
)
$ByteKey              = [Byte[]][Char[]]$Key
$bytes                = [System.Text.Encoding]::UTF8.GetBytes($InputString)
$aesManaged           = [System.Security.Cryptography.AesManaged]::new()
$aesManaged.Mode      = [System.Security.Cryptography.CipherMode]::CBC
$aesManaged.Padding   = [System.Security.Cryptography.PaddingMode]::PKCS7
$aesManaged.BlockSize = 128
$aesManaged.KeySize   = 256
$aesManaged.Key       = $ByteKey
$aesManaged.IV        = $ByteKey[0..15]
$encryptor            = $aesManaged.CreateEncryptor()
$encryptedData        = $encryptor.TransformFinalBlock($bytes, 0, $bytes.Length)
$EncryptedString      = [System.Convert]::ToBase64String($encryptedData)
$aesManaged.Dispose()

Write-Output $EncryptedString
}


function Decrypt-String {
[cmdletbinding()]
param (
    [ValidateLength(32,32)]
    [string]$Key,

    [string]$InputString
)
$ByteKey              = [Byte[]][Char[]]$Key
$bytes                = [System.Convert]::FromBase64String($InputString)
$aesManaged           = [System.Security.Cryptography.AesManaged]::new()
$aesManaged.Mode      = [System.Security.Cryptography.CipherMode]::CBC
$aesManaged.Padding   = [System.Security.Cryptography.PaddingMode]::PKCS7
$aesManaged.BlockSize = 128
$aesManaged.KeySize   = 256
$aesManaged.Key       = $ByteKey
$aesManaged.IV        = $ByteKey[0..15]
$decryptor            = $aesManaged.CreateDecryptor()
$unencryptedData      = $decryptor.TransformFinalBlock($bytes, 0, $bytes.Length)
$DecryptedString      = [Text.Encoding]::UTF8.GetString($unencryptedData).Trim([char]0)
$aesManaged.Dispose()

Write-Output $DecryptedString
}