We propose a new blind certification protocol that provides interesting properties while remaining efficient. It falls in the Groth-Sahai framework for witness-indistinguishable proofs, thus extended to a certified signature it immediately yields non-frameable group signatures. We then use it to build an efficient (offline) e-cash system that guarantees user anonymity and transferability of coins without increasing their size. As required for fair e-cash, in case of fraud, anonymity can be revoked by an authority, which is also crucial to deter from double spending.