A blind oracle is a cryptographic protocol based on zero-knowledge proofs that enable a user to send a confidential message to an entity known as an oracle. The oracle processes the message through operations like signing or encryption without gaining knowledge of the message's contents. The user can then verify the outcome without exposing the message to the oracle.

The Blockstream Jade hardware wallet utilizes this protocol in its oracle-enforced PIN protection feature. This feature encrypts Jade's recovery phrase (mnenomic) to protect against physical threats. It is akin to a virtual secure element that offers additional safeguarding for your funds. It significantly increases the difficulty for potential attackers since they would need to compromise both your locally encrypted flash and the remote PIN oracle. Moreover, this unique security model allows Jade to maintain its open-source nature, as it does not necessitate a built-in secure element.