An instruction decryption arrangement includes an input interface configured to receive an encrypted instruction, a decryption key updater configured to output a decryption key, and an instruction decrypter including a first input connected to the input interface and a second input connected to the decryption key updater, and configured to decrypt the encrypted instruction using the decryption key and to provide a decrypted instruction. The decryption key updater is further configured to update the decryption key using at least one of the encrypted instruction and the decrypted instruction. An alternative instruction decryption arrangement includes a key stream module configured to iteratively determine a key state corresponding to a current instruction for a computing unit and an instruction decrypter configured to receive an encrypted instruction related to the current instruction and decrypt the encrypted instruction using the key state to provide a decrypted instruction.