A recovery key is an optional security feature that helps improve the security of your Apple Account. If you lose access to your account, you can use your recovery key to reset your password and regain access.| Apple Support
Advanced Data Protection for iCloud offers our highest level of cloud data security and protects the majority of your iCloud data using end-to-end encryption.| Apple Support
iCloud uses strong security methods, employs strict policies to protect your information and leads the industry in using privacy-preserving security technologies, such as end-to-end encryption for your data.| Apple Support
This is how to add end-to-end encryption to your iCloud account—and why you should.| Forbes