Embodiments are directed to countermeasures against hardware side-channel attacks on cryptographic operations. An embodiment of an apparatus includes multiple crypto cores; and a current source including multiple current source blocks, the current source blocks including a respective current source block associated with each of the crypto cores, and wherein the current sources blocks are switchable to switch on a current source block associated with each active core of the multiple crypto cores and to switch off a current source associated with each inactive core of the multiple cryptographic cores.