A method and device for protecting encrypted data are disclosed. In an embodiment an integrated circuit includes a secure module including a first register containing a first mask and a second register containing masked data, the first mask and the masked data forming a secret key and a processor configured to generate a second mask and mask the secret key with the second mask when the secret key is not used for an encryption operation and during reception of a validation signal, wherein the first and second registers are disposed in the secure module so that the outputs of the registers are not simultaneously optically viewable.