OPRF

Yandex Deploys OPRF Protocol to Protect Phone Numbers in Mandatory Audience Measurement Data Sharing

Yandex has detailed a cryptographic scheme using Oblivious Pseudorandom Function (OPRF) to help Russian audiovisual services comply with new legislation requiring transmission of user identifiers linked to phone numbers. The approach replaces a naive shared-secret hashing method that created a single point of compromise across dozens of competing companies. Instead, two independent third parties each hold separate secret keys and process blinded elliptic-curve points derived from normalized E.164 phone numbers. Services obtain deterministic identifiers without learning the third-party keys and without exposing raw numbers to the authorized research organization. The design distributes trust, limits offline brute-force attacks to scenarios requiring both keys plus final identifiers, and adds rate limits plus key-rotation capabilities to deter abuse. Yandex positions the solution as a practical compromise between regulatory demands, competitive secrecy, and user privacy.