Absolutely, the text you write is encrypted using aes-256 before being stored on our servers. We're also considering allowing an option to encrypt once more with a custom password set by the writer - the problem with this custom encryption is that if you lose the password you're not able to get your words back.
The encryption key is generated dynamically and it is not stored together with the encrypted content, thus in case of any leakage the words that were written are safe. The writing is decrypted and shown decrypted only to the writer itself and our team doesn't have access to see the words you've written.