In one embodiment, a processing device includes a memory to store an executable program including a multiplicity of encrypted component blocks such that different combinations of blocks selected from the encrypted component blocks are operative when decrypted and executed to perform a same functionally equivalent data transformation, each of the component blocks being operative upon execution to convert input data into output data, and a processor operative to receive a selection of cryptographic keys, decrypt some of the encrypted component blocks using the cryptographic keys such that each one of the some encrypted component blocks is decrypted with a different one of the cryptographic keys yielding a multiplicity of decrypted component blocks, and execute the executable program including the multiplicity of decrypted component blocks to perform the same functionally equivalent data transformation. Related apparatus and methods are also described.