In end-to-end encryption, data is protected by default wherever it goes over its entire lifecycle. Sensitive data is encrypted the moment it is captured, in a point-of-sale (POS) device at a retail store, for example, and stays encrypted or is re-encrypted while it moves between systems and security domains. This notion of encryption as a data “bodyguard” that always accompanies data objects (files, documents, records, and so on) is appealing but raises questions about establishing trust relationships between different domains and interoperability when it comes to key management.

Why is it a disadvantage to have one copy? If you have something important just make another copy somewhere else.

What is end-to-end encryption?
End-to-end encryption utilizes a user-generated, private key to encrypt all entries before they reach Day One servers. With possession of the encryption key held only by the end user, maximum security is assured for journal data.

How do I use this feature?
End-to-end encryption is enabled on a journal-by-journal basis. Go to Journals in Day One's Settings, then select the journal you want to encrypt. Follow the on-screen instructions to complete this process. More instructions are found here.

Being a regular user of a messenger you will not notice any difference in usage. And I think it is stupid to send important information via a usual messenger, cause the information will not be protected for sure.

Thanks. Maybe I will check it out then. It is hard to use something new when you are used to using something else though.

I have heard about telegram's safety a lot lately. But for some reason I still use WhatsApp more than any other messenger cause I like how convenient and easy it is.

By the way, how can anyone be sure that the conversation is fully private or not? Cause I use whatsapp and haven't noticed any invasions of privacy yet.

There is a huge invasion in our privacy nowadays. So private communication totally makes sense to me. Obviously you have to pay for that kind of service.