Deja Q: Encore! Un Petit IBE

摘要

We present an identity-based encryption (IBE) scheme in composite-order bilinear groups with essentially optimal parameters: the ciphertext overhead and the secret key are one group element each and decryption requires only one pairing. Our scheme achieves adaptive security and anonymity under standard decisional subgroup assumptions as used in Lewko and Waters (TCC '10). Our construction relies on a novel extension to the Deja Q framework of Chase and Meiklejohn (Eurocrypt '14).