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Introduction

Introduction and high-level context coming soon.

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Technical Reference

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High-Level Overview

Coming soon.

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Backup Composition

Backup Composition
  • The is a collection of raw files stored locally on the device only. The structure of the is described in the Backup Composition & Sync section.
  • The user encrypts the with a that’s randomly generated by World App.
  • The user then encrypts the with each Factor Secret, creating nn . After the is encrypted with each Factor Secret, the user discards the secret key of the , and stores the public key (which is used to encrypt new versions of the to Sync the backup).
  • All the s are stored in the .
The reason for the layer is that when adding a new , the factor can be added without requiring to create a new . If Factor Secrets were used directly, nn versions of the would need to be stored.

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Factor Secrets

Main Factors are able to derive or store Factor Secrets. A Factor Secret is a key that is used to encrypt the . When decrypting the , the is decrypted first with the Factor Secret and then the Sealed Backup to retrieve the raw files. Each derives its Factor Secret this way:
  • For Passkeys, the Factor Secret is a PRF extension key which allows deriving a deterministic symmetric key.
  • For OIDC, the Factor Secret is a random 32 byte sequence that is generated in the user’s World App and then stored inside Turnkey’s Secure Enclaves as a Private Key. On recovery, the Secure Enclave provably authenticates the user before providing the secret.
  • For iCloud Keychain, a P-256 keypair is generated by the Security framework on iOS and stored in the keychain. The private key is used as a secret to encrypt the .

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Backup Metadata

The is a plain-text file that is stored in the backup service. It generally contains the following information (see source code for most up-to-date information):
  • The ID of the backup
  • The list of .
  • The list of s.
  • The list of s.