It's just encrypted gibberish without the passphrase. Since there's no character limit on the passphrase you can use a 140 character long phrase. Unbreakable.
You could encrypt your private keys and publicly publish them on the Bitcoin blockchain in an ordinal and it wouldn't matter.
Never heard of Edge is it open source? How do you know there isn’t a back door?
It's not open source but it is technically non-custodial.
https://edgeapp.zendesk.com/hc/en-us/articles/7019703449115-Edge-White-Paper
There was a security vulnerability recently back that they had to fix:
https://edge.app/blog/company-news/edge-security-incident-urgent-notice/?af=google-com
