Bip39 Compliant Passphrase Wallet Application that carry out BIP39 only use 2048 iterations as a norm. Growing this parameter will maximize safety towards brute drive assault, but you will need to retail store this new parameter. Use private keys at brainwallet.org, but watch out - it can be very easy https://www.youtube.com/channel/UCUpxfyTJ0fb78SQ55hU6OCw