A method of protecting the integrity of a computer program running on a computer device includes a procedure of detecting whether or not an unauthorized modification of the address space of the program has occurred and terminating program execution if an authorized modification is detected and continuing program execution if no such modification has been detected. A communication method between at least two communication parties of a computing device includes the step of generating at each of the communication parties for every communication sequence at runtime a private key and a public key for a digital signature, making available the public key to the other communication parties and performing the communication between the communication parties using a digital signature based on the private and public keys. Both methods provide improved protection against possible violations of integrity and authenticity by malicious programs on a local computer system.