https://www.bleepingcomputer.com/news/security/whatsapp-now-encrypts-contact-databases-for-privacy-preserving-synching/

The WhatsApp messenger platform has introduced Identity Proof Linked Storage (IPLS), a new privacy-preserving encrypted storage system designed for contact management.

The new system solves two long-standing problems WhatsApp users have been dealing with for years, namely the risk of losing their contact lists if they lose their phone and the inability to sync contacts between different devices.