wiping SSD with GParted - ran into problem

Hi everyone,

I used DBAN first to wipe my HDD, but i also used it for the SSD, before realizing its not for SSDs.

Anyway, now I am using Gparted. My SSD is a 256GB Samsung 840 Pro.
I am following these steps: Use GParted to secure erase SSD - G.SKILL TECH FORUM

BUT, when I have to write 'hdparm --security-erase NULL /dev/sda' - it says:

security_password=" "
/dev/sda: Permission denied

Guess that means password is wrong?
I tried this: just after entering the desktop thing, i unplug the power of my SSD then plug back in. I read that it can get frozen so you just have to do that.
But it still didnt want to accept security erase and still said access denied.

Please, what the hell do I do?

Or should I use something else but gparted to wipe the SSD? the samsung magician software cannot create an iso for the samsungs secure erase, brcause I ran the magician on the other PC and it cannot detect any SSD (because there is not any). so the erase thing doesnt want to give me tbe iso.

Please, help, i am unexperienced in this and doing it for the first time!

Thanks in advance for help

Everything is good, installing windows now..

Thanks :)

I read that before already. It suggests HDDErase, which is outdated and could cause problems, and Parted Magic, which is no longer free.
I did (try to) use Gparted, which is a part of Parted Magic.