Abstract
This disclosure describes zero-access storage of voicemail and similar recorded messages:
a carrier, PBX, VoIP service, contact centre or visual-voicemail provider records and stores
a message but can never read it. At deposit time, while the customer may be offline, the
recording and its metadata are sealed to a customer-controlled public key. The private key
stays in customer custody: on a phone or browser, a hardware token, a passkey PRF, a
password-derived wrap, a customer-managed KMS or HSM, or split custody. Keys and
ciphertext reach the customer by many routes: decryption APIs, browser or app
decryption, streaming, DTMF unlock digits, DTMF/FSK/fax-style carriage over the voice
channel, QR/NFC/Bluetooth, SMS/RCS, email, SIP INFO or RTP events, USB tokens, or
delivery to customer storage. A phone-channel variant plays the message in an ordinary
call after a separate API call authenticates the customer and releases the key, with
ephemeral server-side decryption wiped at hangup. Transcription runs on the device or in
an enclave and notifications carry no content. The core idea is old; this paper dates the
concrete combinations.
Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 License.
Recommended Citation
Boll, Joe, "Zero-Access Voicemail: Provider-Blind Recording Sealed to Customer-Held Keys, with Key Transmission and Out-of-Band Release Variants", Technical Disclosure Commons, ()
https://www.tdcommons.org/dpubs_series/12741