Adventurer #06 28 февраля 1997

Программирование

Exchange of experience - Methods for protecting software code.

    Methods of protection code



            Review article


     To date, the image do a few methods to protect software 
code. Enumerate them.


1.Zaschita inverting the mask.

  (In the hoi polloi - KSORKA)

 Widely known and used method.
 Often used with the application of quality space in the mask 
register R and is characterized by Ed Kim monotony, though 
occasionally getting this program are masterpieces. Ma 
loeffektiven, although they often require no little time for 
hacking. Shining example  use: copier L-Copy (AB torus: Laptev).


2.Zaschita with different "perverted".

 "Distorted" - code that is written with the use of specially 
complicated algorithms with  to hide the direct address or 
launch a sub or entangling itself  program. Different to 
lichestvom unlimited options, but uses  relatively rare, 
because designed to  poor knowledge of assembler and principles

 programming. Currently, small loeffektiven. Examples of common 
daily activities locally, such as: the machinations of the 
stack,  conditional jumps and "implicit" exit

 through the stack at the correct address.

3.Metod using the PI code, or just
  novidnostey threaded code.

 PI code - assembler for an abstract ma bus, a sort of 
intermediate stage between  machine code and high-level 
language.  Threaded code - a specific version of the same PI 
code. 

 Very cool method of protection, in general, on hozhy on method 
2, but only rarely  applicable to the class PC Spectrum. Not 
wealth: "not weak" code size and more  lower than the "pure" 
code bystrodeys tvie. Effectiveness of the method is very high  
and breaking of the teeth only very experienced  programmers. 
Example: Any program  compiled in Pascal language Forth.

 At such a code can Spectrum'e generating vat compiler BLAST 
(the rest is generated ruyut "perverted", supra). 

4.Metod using kriptografiches
  FIR algorithms and passwords.

 Widely used in powerful PCs and
 different spyware "offices" method. Based on the van on a 
variety of mathematical algorithms for the FIR, the purpose of 
which - by  macabre calculations obtained from the source

 information block and a key Massie Islands (password), a file, 
decode  which can only be one who has this


 password. Hack a file can only be
 after studying forty pounds of a special mathematical 
literature, after  then you can safely offer their

 candidature for the post of CIA director.
 At Spectrum'e not effective because Password
 none but ourselves can not show,
 another couple of days later he learns all the
 country.

5.Metod which is based on IM2.

 In contrast to the above I do not
 caught, so that explains the speculative but. Based on 
"linking" the main prog Ramm and ISR (from the English .- 
"routine of processing interrupts" - Interrupt Service  
Routine) to organize the control  (For example, assume the 
checksum)  main program for infringing ments outside. Then 
opens wide  field experiments. You can, for examples py, 
organize data transmission through  ISR data from one array to 
another 

 or use the ISR for the dynamic
 encoding unused for the current
 time routines, etc. Complexity method in appropriate depth of 
the  and "matching" algorithms and ISR programs,

 to avoid the bugs and delays in work
 program because of aperiodic ISR,
 related to the complexity of determining time to time interval 
from DI EI. Very promising and  promising method.


     It seems that all other options
protection of software code are nothing more than special cases 
of the above or combinations thereof. Use of undocumented 
commands Z80 is not included in the article because of the 
trivial - The last time they actually are well known to all.


     I will be glad of any information on how to
information security and cooperation in this
area.

       Spinel Roman E. (SHRSOFT).