Bip39 Node Js To make a seed phrase by doing this, You'll have a calculator that includes a RANDOM functionality (for building entropy). Learn more about producing a seed phrase using an offline calculator listed here. Use private keys at brainwallet.org, but watch out - it may be very easy https://webdirectoryone.com/listings13016943/bip39-to-private-key-the-fact-about-bip39-phrase-that-no-one-is-suggesting