This conversion seems to be related to some attempts of conversion of various WhatsApp message backups, including the now old and somewhat obsolete .crypt8 files. Generally speaking, you can convert WhatsApp backups to the latest version used if you import them to the app and do the recover procedure. Sometimes, may require reinstalling of the app.
Convert WhatsApp Messenger message database to WhatsApp Messenger message database backup.
We found 2 software records in the database related to .db to .db.crypt8 file format conversion.
Articles and other information relating to db into db.crypt8 conversion:
How to convert WhatsApp CRYPT files - Decrypting WhatsApp message databases
Blackberry mobile phones and devices software - convert db to db.crypt8 on Blackberry
Cross-platform smartphone messenger also available for BlackBerry
Convert from db file format
The tables with software actions are a good pointer for what a certain program does with various file types and often may give users a good hint how to perform certain file conversion, for example the above-mentioned db to db.crypt8. However, it is not perfect and sometimes can show results which are not really usable because of how certain programs work with files and the possible conversion is thus actually not possible at all.
Windows Phone / Windows 10 Mobile software - convert db to db.crypt8 on Windows Phone
Instant messaging client for Windows Phone OS