Alexandre Duc (EPFL,
Dimitar Jetchev (EPFL,
We prove that if one can predict any of the bits of the input to an elliptic curve based one-way function over a finite field, then we can invert the function. In particular, our result implies that if one can predict any of the bits of the input to a classical pairing-based one-way function with non-negligible advantage over a random guess then one can efficiently invert this function and thus, solve the Fixed Argument Pairing Inversion problem (FAPI-1/FAPI-2). The latter sheds some light on the security of various pairing-based schemes such as the identity-based encryption scheme of Boneh--Franklin, Hess' identity based signature scheme, as well as Joux's three-party one-round key agreement protocol. Moreover, if one can solve FAPI-1 and FAPI-2 in polynomial time then one can solve the Computational Diffie--Hellman problem (CDH) in polynomial time.
Our result implies that all the bits of the one-way functions defined above are hard-to-compute. The argument is based on a list-decoding technique via discrete Fourier transforms due to Akavia--Goldwasser--Safra as well as an idea due to Boneh--Shparlinski.