'Safe' from the sense that it makes it difficult to compromise the security credentials of your account. However, this will do nothing to stop you from inadvertently uploading ransomware to your account.
This seems very similar to SQRL.... https://www.grc.com/sqrl/sqrl.htm how much does it differ?
well actually dropbox is highly relevant enough for the technology, i could grab a depth within this concept, just point i was lacking is about SQRL
AFAIK Dropbox is an untrusted computer.
https://en.wikipedia.org/wiki/Condoleeza_Rice#Role_in_author...