I had a need to decrypt some Cisco VPN enc_GroupPwd entries, but didn't want put client info into random web forms, and didn't to install python to use the first result I found. So I converted the python to PowerShell, and here we are :)

Decrypt-CiscoPassword.ps1

# Converted from https://github.com/axcheron/cisco_pwdecrypt/

[Diagnostics.CodeAnalysis.SuppressMessageAttribute('PSAvoidUsingPlainTextForPassword', 'CiscoPassword')]

[CmdletBinding(PositionalBinding = $false)]

[OutputType([String])]

Param (
    [Parameter(Mandatory = $true, ValueFromPipeline = $true)]
    [ValidateNotNullOrEmpty()]
    [string]
    $CiscoPassword
)

Begin {
    $3DES = New-Object -TypeName Security.Cryptography.TripleDESCng
    $SHA1 = New-Object -TypeName Security.Cryptography.SHA1Managed
}

Process {
    $HexStrings = $CiscoPassword -split "(?<=\G\w{2})(?=\w{2})"
    $ByteArray = $HexStrings | ForEach-Object -Process {[Convert]::ToByte($PSItem, 16)}

    $ht = $ByteArray[0..19]
    $enc = $ByteArray[40..($ByteArray.Count-1)]
    $iv = $ByteArray

    $ht[19] += 1
    $h2 = $SHA1.ComputeHash($ht)

    $ht[19] += 2
    $h3 = $SHA1.ComputeHash($ht)

    $key = $h2 + $h3[0..3]

    $h3des = $3DES.CreateDecryptor($key, $iv[0..7])
    $cleartext = [Text.Encoding]::UTF8.GetString($h3des.TransformFinalBlock($enc, 0, $enc.Count))

    return $cleartext
}

End {
}

Your mileage may vary. This worked for me, but I haven't tried to make it robust or work for all types of enc_GroupPwd, etc.