An encryption device performs elliptic curve encryption using a secret key. The encryption device includes an operation unit for performing scalar multiplication of a point on an elliptic curve a storage unit having a plurality of data storing areas and a determiner unit for determining, in accordance with a bit sequence of a given value (d) and with a random value (RNG), an address of one of the plurality of data storage areas that is to be coupled to the operation means for each scalar multiplication.