# Glossary

You can't use a tool effectively if you don't know the terminology specific to the corresponding subject. The following glossary explains terminology used in VMProtect. The glossary is not intended to be exhaustive, so some terms may provide meanings that differ from classic ones.

Bytecode - the code received after transcoding commands of the real processor to commands of the virtual machine.

Virtualization - a process that transforms a part of the executable code of the application to commands of the virtual machine featuring command system, architecture and operational logic that are unknown to a potential hacker. Virtualized fragments of code are executed by the interpreter of the virtual machine without transforming them to machine language code of the physical processor. Generally, reverse engineering of virtualized fragments comes down to building a disassembler with the same architecture as the processor the virtual machine imitates and analyzing of the resulting disassembled code.

Virtual machine - a program code directly executing bytecode in the protected application.

Watermarks - a unique for each user array of bytes that allows to definitely identify a legal owner of the hacked copy of the program.

Mutation - replacing an original command with an analogue or with a certain set of commands producing the same result

Obfuscation - a group of methods and techniques intended to complicate analysis of a program code. Depending on the programming language a protected program is written on, different obfuscation types are used. Obfuscation of applications written on interpreting languages (Perl, PHP and others) is made through modifying the source code: comments are removed, variables are given senseless names, string constants are encrypted and so on. Obfuscation of Java / .NET applications is performed through transforming the bytecode processed by the virtual machine. Obfuscation of compiled programs relies on modifying machine language codes: the obfuscator adds various "garbage" commands, "dead code", random jumps. Also, original commands mutate, a part of operations is moved to the stack, and a number of structural (or less frequently mathematical) transformations is made. Reverse engineering of obfuscated fragments of code attempts to bring the fragments back to their original state, and that is a time-consuming task as long as obfuscation is done properly.

Protector - software intended to protect other programs from being hacked. The majority of today's protectors do not modify the source code of an application, packing or encrypting the app instead. The main focus is put to protecting the unpacking/decrypting program or procedure.

Entry point - the initial address execution of the application loaded into the memory starts from.

Packing - a way to protect the program code by compressing the executable file of the program and/or libraries using non-typical algorithms. The protected fragments of code are compressed by the packer, and unpacked completely or partially at user's side when the application is executed.

Encryption protects a part of the application's code with strong cryptographic algorithms. Software protected by encryption requires an end-user to enter the activation code to remove limitations set by the developer for the unregistered version of the program.

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