Encrypted key file and passphrase are processed only in this browser. The mailbox receives only an authenticated ciphertext frame.
Key export: frs-recovery-export-v1. Frame: AES-256-GCM v1. Epoch: cloudrun-api-39labo-20260526234312 — https://github.com/39labo/fm-receiver-archive/releases/latest/download/future-sender-archive.zip