A method of operation concealment for a cryptographic system includes randomly selecting which one of at least two cryptographic operation blocks receives a key to apply a valid operation to data and outputs a result that is used for subsequent operations. Noise can be added by operating the other of the at least two cryptographic operation blocks using a modified key. The modified key can be generated by mixing the key with a block-unique-identifier, a device secret, a slowly adjusting output of a counter, or a combination thereof. In some cases, noise can be added to a cryptographic system by transforming input data of the other cryptographic operation block(s) by mixing the input data with the block-unique-identifier, device secret, counter output, or a combination thereof. A cryptographic system with operation concealment can further include a distributed (across a chip) or interweaved arrangement of subblocks of the cryptographic operation blocks.