oprf

OPRF

Oblivious pseudo-random function over an elliptic curve (ED25519)

Installation

npm install oprf

Security Guarantees

A client has input x while a server holds key k. The client receives the output of f_k(x) for some pseudorandom function family f_k. The server learns nothing.

Dependencies

• elliptic
• libsodium.js

Steps

1.) Client: hash input and mask it using a randomly generated 32-byte number

function maskInput(input: string): maskedData

2.) Server: salt the masked point using a secret key

function saltInput(maskedPoint: Array<Number>, key: string): Array<Number>

3.) Client: unmask the salted point from the server to get a high-entropy output

function unmaskInput(salted: Array<Number>, mask: BN): Array<Number>

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Implementation inspired by Burns et. al. https://pdfs.semanticscholar.org/5d33/ea1d3fda454875a6a6ee7c535c80c74af512.pdf