PowerShell – Symmetric Encryption

Alex Ø. T. Hansen

17/05/2018

PowerShell – Symmetric Encryption

You can use this PowerShell function to encrypt/decrypt data with a secret key.

I re-wrote the functions from Travis Gan, for a better overview and also added comments to the code.

Use free of charge!

#Generate a secret key.
Function Set-SecretKey
{
    [CmdletBinding()]
    Param
    (
        [string]$Key
    )

    #Get key length.
    $Length = $Key.Length;
    
    #Pad length.
    $Pad = 32-$Length;
    
    #If the length is less than 16 or more than 32.
    If(($Length -lt 16) -or ($Length -gt 32))
    {
        #Throw exception.
        Throw "String must be between 16 and 32 characters";
    }
    
    #Create a new ASCII encoding object.
    $Encoding = New-Object System.Text.ASCIIEncoding;

    #Get byte array.
    $Bytes = $Encoding.GetBytes($Key + "0" * $Pad);

    #Return byte array.
    Return $Bytes;
}

#Encrypt data with a secret key.
Function Set-EncryptedData
{
    [CmdletBinding()]
    Param
    (
        $Key,
        [string]$TextInput
    )
    
    #Create a new secure string object.
    $SecureString = New-Object System.Security.SecureString;

    #Convert the text input to a char array.
    $Chars = $TextInput.ToCharArray();
    
    #Foreach char in the array.
    ForEach($Char in $Chars)
    {
        #Append the char to the secure string.
        $SecureString.AppendChar($Char);
    }
    
    #Encrypt the data from the secure string.
    $EncryptedData = ConvertFrom-SecureString -SecureString $SecureString -Key $Key;

    #Return the encrypted data.
    Return $EncryptedData;
}

#Decrypt data with a secret key.
Function Get-EncryptedData
{
    [CmdletBinding()]
    Param
    (
        $Key,
        $TextInput
    )

    #Decrypt the text input with the secret key.
    $Result = $TextInput | ConvertTo-SecureString -Key $Key | ForEach-Object {[Runtime.InteropServices.Marshal]::PtrToStringAuto([Runtime.InteropServices.Marshal]::SecureStringToBSTR($_))};

    #Return the decrypted data.
    Return $Result;
}

#Text you want to encrypt.
$TextInput = "This is my secret text.";

#Create a secret key (between 16 or 32 in length).
$Key = Set-EncryptedKey -Key "<My secret key>";

#Encrypt data with the secret key.
$EncryptedData = Set-EncryptedData -Key $Key -TextInput $TextInput;

#Decrypt data with the secret key.
$DecryptedData = Get-EncryptedData -Key $Key -TextInput $EncryptedData;

#Show decrypted data.
Write-Output ($DecryptedData);

#Generate a secret key.

Function Set-SecretKey

{

[CmdletBinding()]

Param

(

[string]$Key

)

#Get key length.

$Length = $Key.Length;

#Pad length.

$Pad = 32-$Length;

#If the length is less than 16 or more than 32.

If(($Length -lt 16) -or ($Length -gt 32))

{

#Throw exception.

Throw "String must be between 16 and 32 characters";

}

#Create a new ASCII encoding object.

$Encoding = New-Object System.Text.ASCIIEncoding;

#Get byte array.

$Bytes = $Encoding.GetBytes($Key + "0" * $Pad);

#Return byte array.

Return $Bytes;

}

#Encrypt data with a secret key.

Function Set-EncryptedData

{

[CmdletBinding()]

Param

(

$Key,

[string]$TextInput

)

#Create a new secure string object.

$SecureString = New-Object System.Security.SecureString;

#Convert the text input to a char array.

$Chars = $TextInput.ToCharArray();

#Foreach char in the array.

ForEach($Char in $Chars)

{

#Append the char to the secure string.

$SecureString.AppendChar($Char);

}

#Encrypt the data from the secure string.

$EncryptedData = ConvertFrom-SecureString -SecureString $SecureString -Key $Key;

#Return the encrypted data.

Return $EncryptedData;

}

#Decrypt data with a secret key.

Function Get-EncryptedData

{

[CmdletBinding()]

Param

(

$Key,

$TextInput

)

#Decrypt the text input with the secret key.

$Result = $TextInput | ConvertTo-SecureString -Key $Key | ForEach-Object {[Runtime.InteropServices.Marshal]::PtrToStringAuto([Runtime.InteropServices.Marshal]::SecureStringToBSTR($_))};

#Return the decrypted data.

Return $Result;

}

#Text you want to encrypt.

$TextInput = "This is my secret text.";

#Create a secret key (between 16 or 32 in length).

$Key = Set-EncryptedKey -Key "<My secret key>";

#Encrypt data with the secret key.

$EncryptedData = Set-EncryptedData -Key $Key -TextInput $TextInput;

#Decrypt data with the secret key.

$DecryptedData = Get-EncryptedData -Key $Key -TextInput $EncryptedData;

#Show decrypted data.

Write-Output ($DecryptedData);

About Alex Ø. T. Hansen

Experienced advanced operations engineer with a demonstrated history of working in the information technology and services industry. Skilled in Windows Server, Azure, Ethical Hacking, Office 365, Exchange, Jenkins, SCCM, Octopus Deploy and PowerShell to name a few. Strong engineering professional with a big passion for knowledge.

3 Comments

Ramesh

16/10/2020 at 07:52

I am not able to run your script , it is like failing to pass write values to Key & Text.
#Encrypt data with a secret key.

ex: Set-EncryptedData 28122012 WelomeToPowerShellEncryption

failed that

ConvertFrom-SecureString : Cannot bind parameter ‘Key’. Cannot convert value “28122012” to type “System.Byte”. Error: “Value was either too large or too small for
an unsigned byte.”
At C:\Users\rkunamneni\Desktop\powershell\Vfs-Scripts.ps1:616 char:80
+ … ata = ConvertFrom-SecureString -SecureString $SecureString -Key $Key;
+ ~~~~
+ CategoryInfo : InvalidArgument: (:) [ConvertFrom-SecureString], ParameterBindingException
+ FullyQualifiedErrorId : CannotConvertArgumentNoMessage,Microsoft.PowerShell.Commands.ConvertFromSecureStringCommand

will you please give me an example how to run your script?

Ramesh

16/10/2020 at 08:10

#Text you want to encrypt.
$TextInput = “This is my secret text.”;
should work now
#Create a secret key (between 16 or 32 in length).
$Key = Set-SecretKey -Key “28122012AnikaKunamneni”;

#Encrypt data with the secret key.
$EncryptedData = Set-EncryptedData -Key $Key -TextInput $TextInput;

#Decrypt data with the secret key.
$DecryptedData = Get-EncryptedData -Key $Key -TextInput $EncryptedData;

#Show decrypted data.
Write-Output ($DecryptedData);

amin benkhaled

28/04/2024 at 08:36

To fix the Script Change the name of the function ‘Set-SecretKey’ to ‘Set-EncryptedKey’
this Fixed the error for me

PowerShell – Symmetric Encryption

3 Comments

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