Proof of certification now possible with SIGN web app
Sign web app is now live on mainnet and this allows you to prove whether a particular file exists or not on Waves blockchain. Developers behind SIGN app have churned out v0.9.3 that adds ability to revoke certification.
Also, the app gives enhanced warning about saving seed on initial connection. Other than that, many user interface related bugs. SIGN web app is using Waves Signer to connect your account and sign all transactions. To import an existing account, you will have to first add it in waves.exchange.
SIGN web app will never ask you to enter your private key as they are managed by Waves exchange. So, if a similar app is asking you to enter your private key, it is likely a scam.
To get started, enter your password or create a new account. If you already have an account, they will be listed on next screen. Then, you will be connected and be able to use the application. After that, click on manage accounts to access Waves exchange and get your recovery account seed. Make sure to write it down and keep it in safe place.