International Association
for Cryptologic Research

In this short note, we present a simplified (but slower) version Clapoti of Clapotis, whose full description will appear later. Let ?/?_? be an elliptic curve with an effective primitive orientation by a quadratic imaginary order ? ⊂ End(?). Let ? be an invertible ideal in ?. Clapoti is a randomized polynomial time algorithm in ? ((log Δ_? + log ?)^?(1) ) operations to compute the class group action ? ↦ ?_? ≃ ?/?[?].