CAN CRYPTOGRAPHY PREVENT COMPUTER VIRUSES PPT And Paper Presentation

Some computer virus authors have made use of cryptography themselves, in attempts to make their creations more difficult to detect or more difficult to analyse, or as part of the destructive or annoying payloads they carry. While cryptography does not play a key role in most of the viruses currently responsible for the virus problem, the issue of cryptography in computer viruses is worth at least a passing glance. The most common use of encryption in computer viruses is as part of polymorphism. A polymorphic virus is one that changes form as it spreads, so that two different files infected with the virus will not necessarily have any significant byte-strings in common. In machine-language viruses, polymorphism is usually achieved by splitting the virus into three different sections: a short piece of decryptor code, a cryptographic key, and the main functional part of the virus. When the virus creates a new copy of itself, it selects a new cryptographic key, encrypts the main functional part of itself with that key, and generates (using any of a variety of methods) a new implementation of the decryptor code.