Shulou(Shulou.com)06/03 Report--

In the computer field, program shelling means that a "shell" program is executed before the original program is run, and then the program is returned to the original program. The advantage of this is that the real entry point (OEP) of the executable program can not be easily found through conventional cracking methods, which can effectively prevent cracking of the source program and protect important information data.

Shell encryption is divided into camouflage shell, compression shell and other types, although the implementation details of the shell method are different, but its core encryption principle is unchanged, that is, to establish a separate protection mechanism outside the original program. Therefore, no matter for the source program to do compression, encryption or address disruption and other operations, the complete source code must be restored, so that it can work normally. This is a security risk of shell encryption, because shell encryption can be bypassed or stripped by many shelling software. Now there are a lot of free shelling software on the network, which can be easily shelled, so it is unwise to protect the source program by adding a shell.

Another small drawback of shell encryption is compatibility. Because of the differences of executable files in different system platforms, there are different requirements for shelling. For example: DOS executable file matters. Com at the end of the file, and there is no header, the default program execution address is 0x100ching Win32 platform PE file, does not support self-loading, the program needs to use its own method to manage data, so the standard is very inconsistent, resulting in the compatibility problem of shell encryption is not easy to solve.

In addition to shell encryption, there is also an algorithm transplantation scheme for PC software encryption, which is more popular in the market. The basic principle is to transplant part of the code functions of the executable file to another security hardware platform to ensure that the original program code is incomplete. The advantage of this is that the existing program and the transplanted program must be cracked together in order to achieve real cracking. For this encryption scheme, the security hardware platform outside PC is very important, the most common is the algorithm transplant encryption dog, generally choose the embedded security chip with very high security level to complete the operation of the transplant code. Because the security chip has many anti-cracking mechanisms, the code running inside it can not be read illegally, as long as the transplanted code is selected reasonably, it can greatly improve the security of executable software.

However, this software encryption scheme also has shortcomings, it requires developers to have a certain embedded programming ability, research and development will need to invest more time.

The above two encryption schemes have their own advantages and disadvantages, and users need to choose the appropriate encryption scheme according to their actual needs and application scenarios. If users pay more attention to security, then the encryption dog of the algorithm transplantation scheme will be more suitable.

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