KR20040027826A - A method to protect computer software using file transformation - Google Patents

Abstract

PURPOSE: A method for protecting software using computer file transform is provided to prevent a stored important document from outflow through illegal copy or hacking and inadequate use by setting a password written by a user to the document. CONSTITUTION: For protecting a computer file, a matching file is formed by using the matching division for transforming the computer file. The first matching file is provided to the user. A use right of the user is certified. Without storing an additional matching file matched with the first matching file in a user computer, the computer file is remotely installed to the user computer by executing only an install file.

Description

A method to protect computer software using file transformation}

The present invention deals with an encryption method for preventing unauthorized copying, hacking prevention, and protecting various computer files by using file division and modification.

Currently, the software program is used to prevent unauthorized copying. The software is registered through the Internet after the software program is installed or after the software program is installed. However, non-registrants restrict their use or encourage the purchase of licenses. As a result, crack software programs are being developed and distributed over the Internet to skip or ignore such authentication or registration processes.

In addition, in order to prevent hacking, it is intended to prevent hackers from accessing important data by devising a multi-dimensional way to prevent hackers from accessing those who want to prevent hacking, but this also does not completely prevent hackers from hacking.

In addition, in case of individuals, in order to prevent others from accessing and using important documents created or software programs and various important files owned by individuals, encryption is performed during compression or encryption during the storage of documents. Although it uses a method of restricting the use of others that it does not know, this method also modifies the file using various methods when encrypting, but the password entered by the user as a password is stored in the encrypted file. Because of this, hackers can hack at any time to find out the password.

For this reason, after software developers sell only a few hundred copies of the software they have developed over the years with huge amounts of money, unauthorized copies of the software are already on the market, or software products developed at great expense are hacked onto the Internet by hacking. In addition, the important documents are used by various methods of hacking techniques to cause unauthorized problems.

The present invention is devised to prevent unauthorized use of important documents stored by unauthorized copying, leakage of important file data through hacking, and encryption created by individual users, which is contrary to the developer's intention in the process of supplying existing software. .

In detail, to prevent unauthorized copying of the target software (software that requires the consent of the developer for using the software: paid program software, various paid files supplied through the Internet, and documents encrypted by document creators, etc.). The file included in the software is divided into two or more files according to the principle of FIG. 1, and the divided files must be supplied with matching files in order to use one file through matching.

Such a matching partition is not only the meaning of partitioning, but also a dummy matching variable so that the primary matching file itself has no meaning, and the software is modified by modifying the dummy, and when installing or using the software later, the user authenticates the dummy. This includes removing the variable from the server.

In other words, if you want to supply software to 100 people when dividing one software, make 100 matching files by making 100 matching files according to 100 criteria and provide the first matching file to the user. If additional matching file is managed by server and provided remotely only during software installation, user cannot have additional matching file, it can be installed remotely only if they want to install, and the first matching file needs to be shared before user authentication process is required. It becomes impossible to use it.

In addition, the number of times the user installs the software is controlled by the server, and the number of installments can be determined at no additional cost through the purchase of the program. If the cost is variably calculated according to the number of installations, the problem of sharing personal information can also be solved, which can prevent indiscriminate sharing of software.

Thus, a file named A is divided by the criteria of A ', so that A_1, A_2, A_3,. . . If it is divided into A_1, A_2, A__3,. . . Is required, and the file named B works the same. To use the file A, A_1, B_2, B_3,. . . You will not be able to use the software with such files.

That is, even if A and B are the same file, they are divided according to different criteria, such as A_1, A_2, A_3,. . . And B_1, B_2, B_3,. . In order to use A_1, A_1 + A_2 + A_3 +,. . . Must be made through A, and in order to use B_1, a file named B should be composed by receiving B_2 or less. In this case, when the user wants to use and use A_1 and B_2, or wants to use A_2 and B_1, data overlap or data loss occurs as shown in Fig. 1_B of FIG. 1, and thus cannot perform the function of the original software.

In this case, the first matching file may be defined as a file which may be provided first among the matching files (the file matching A_1 of FIG. 1 is A_2 and the file matching B_1 is B_2), and the one-character matching file A file that is provided later that matches the primary matching file for use is defined as an additional matching file. In this case, the matching file may be composed of only the primary matching file through file transformation without additional matching file, and each primary matching file. And additional matching files may consist of two or more files.

In the figure, in order to fit each block as in a computer game Tetris, a block matching each block is required.

In addition, suppose that 100 files to be hacked are prevented and each file is divided into 10 files. In this case, a total of 100 * 10 = 1000 partitioned files exist. even going to import because you can not know if this combination should be complete file by hacking the files, if you want to create arbitrarily to the completed file to the file through a combination, to present the number of cases is close to the next infinity, look compute, ₁₀₀₀ C ₁₀ = 1000! / (100-10)! (10)! = 26340956046l970212832400 and thus finding one file with a combination requires almost infinite number of operations, and ₁₀₀₀ P if the combinations must be in order to restore a single file. ₁₀ becomes the case and the number becomes larger.

Therefore, even if a file is hacked and taken, it cannot be used, and it is useless. In order to figure out which data is used to construct a file called A through the server's CPU hacking, it is necessary to watch the CPU processing for a long time. It is impossible to extract the process by which all files of the file are used, and finding the connection path of each partitioned file by hacking the corresponding program installed on the server complicates the information extraction. If you change the file name from time to time through the program, you will not be able to use it even if you get the necessary information through CPU hacking.

In the case of important documents created by individuals, passwords are protected to prevent others from viewing them. In this case, all characters that a user enters for passwords are recognized by the computer as numerical values. The document creator or self-accessible document may be divided and mixed in each byte unit of the file, or divided and mixed through dilution of each byte, or by dividing and mixing the physical areas of the created document. When a password is entered to browse the file, it is not necessary to store the password to determine the correctness of the password, making it impossible to find the password through document hacking.

In addition, the number of characters represented by the keyboard keys commonly used by individual users of the computer is over 126 (numbers, symbols, uppercase letters, lowercase letters, Korean consonants, vowels). I would like to suggest a method to protect various software products by making it impossible to find the password of the encrypted document or the encrypted file arbitrarily and probabilistic with the probability of 1/126 ⁷ = 1/627485170000000.

Referring to the configuration and effect of the present invention in detail.

1 is the principle of file division in the present invention

2 is an encryption method in which a password is not stored in an encryption file

3 is a data file partition for hacking prevention

* Explanation of Terms in Drawings *

A, B: A and B are the same software (program files, document files, etc.) with the same performance

A_1, A_2, A_3,. . .: Computer file dividing software A according to certain criteria

B_1, B_2, B_3,. . .: Computer file that divides Software B according to its criteria

A_B: File, data overlap, or loss that consists of an inappropriate combination of split files occurs

2_1: Example of encryption according to each password input value

2_2: Example of operation of document based on password when entering password for encryption

2_3: Example of recovering documents in reverse order of manipulating documents according to password criteria when entering a password for decryption

P1, P2, P3, P4: Example of dividing the picture file for visual explanation. Combine P1 and P3 to make a complete picture. Combine P1 and P2, P1 and P4, or P2 and P4 to see the correct picture. none.

In order to achieve the object of the present invention, in order to prevent unauthorized use of the target software, the file is divided by the principle as shown in FIG. 1, but does not end in one division for one software, For each user, file splitting is done by several criteria.

In other words, if a partition such as A of FIG. 1 is partitioned to provide a user named A, and a partition such as B is partitioned to be provided to a user named A, the user A and A may exchange files owned by the user. In addition, it can not be provided to users of additionally existing bottles, and even if provided, the bottles will not be able to use the files, or they will be divided once for one file and share some of the divided files to users. If you allow them to do this and do not provide the rest of the files, they will be managed thoroughly by the server, which will prevent unauthorized copying and use of the files.

In this method, as shown in FIG. 1, each of the divided files is not able to use the remaining files unless each of the divided files is provided with each other, so that some of the divided files are not provided. In order to use a file, a partitioning method for partitioning a file so that another file corresponding to the file is required is defined as a matching partition, and the partitioned file is defined as a matching file.

In this case, it is not meaningful to exchange matching files between users, because an additional matching file required for use of the primary matching file cannot be obtained, and user authentication is required to obtain an additional matching file.

That is, if the program software named A is divided into A_1, A_2, A_3, ..., etc., the file divided into A_1, A_2, A_3, ..., etc. must be supplied to install or use the program software. do.

However, by dividing a file called B = A (the program software of A and B are the same software), B_1, B_2, B_3 ... (A_1 ≠ B_1, A_2 ≠ B_2, A_3 ≠ B_3,..., Ie A_1, 2 , Files of 3,... And files of B_1, 2, 3,... Are not the same), A_1, 2, 3,. . Some of them are provided as a primary matching file first, and then additional matching files are provided through user authentication, etc. In the case of providing a file in the form of a file, all files are retained by users and cracks are possible. Only the installation process is supported.

However, even in this case, there is a program (Ghost) that backs up a program already installed on the hard drive so that it can be installed on another computer, but there is also a program (Phantom) that prevents it.

This means that this type of backup method can be prevented through programming.

In some cases, the program software may be a single executable file. However, in general, the program software is composed of a large number of combinations of files. Is divided into X + Y and Z when the file is composed of X, Y and Z), and the program consisting of X, Y and Z is divided into X, Y_1, Z_1 and Y_2, Z_2 (Y_1 + Y_2 = Y, Z_1 + Z_2 = Z) may be divided.

In the case of the method used for partitioning, a process of dividing a file during compression and a method of directly dividing a target file of a target software are also possible.

If we look briefly at the principle of partitioning, the principle of partitioning can be divided into partitions of sets, partitions of characters, partitions of bytes, and so on. How to organize each matching file by extracting each one and inserting it into the matching file, and breaking each piece of software consisting of letters such as documents into letters and, if necessary, breaking the broken units of letters by a certain standard. Think about how to mix and match files.

In addition, a method of dividing by byte can be considered, which is one of the methods of dividing a file.

Some of the files divided in this way can be downloaded or shared for free (in this case, the file structure consists of files that are available to all users: primary matching files, and additional matching files). When sharing is used, one of the divided files has a function of inducing program software installation.

That is, the first step is to download the first matching file, which is divided and matched through this file, to authenticate the user, and to install the additional matching file instead of downloading the additional matching file remotely through the network. Installation is made through a process that includes the step of receiving.

In other words, the additional matching file installation support does not provide the additional matching file completely, but only supports the installation process with the stock price matching file left on the server.

As a result, the user cannot retain additional matching files.

In this case, the software for inducing the installation of the program software may be shared between individual users and may include some of the divided files, thereby downloading the primary matching file or additional matching file for the installation of the program software. In order to use this primary matching file, an additional matching file matching this primary matching file must be provided.

So far, the example of file division in three stages has been described, but only two stages of matching division are possible, and the primary matching file only needs to include a function of inducing installation.

However, in the case of an additional matching file for installation here, instead of downloading the file directly to the individual user from the server, if the file itself is left on the server and supported only for installation online, the individual user needs to retain the entire file. Software developers can minimize the possibility of unauthorized copying by providing the entire software.

In addition, in the case of a video or the like, when a service is to be provided through the web, the file is divided into two or more, some of them are shared among users, and a file owned by a user and a file serviced by a server must be combined. If you enable it, you can provide the corresponding service while minimizing the load on the server.

In addition, in supplying the software, if a dummy variable is assigned to the software to be supplied or if the user wants to execute it on the user's computer through another operation modification, the proper execution process may not be performed.

In other words, when a dummy variable is added or a manipulated file is to be installed, a dummy variable is removed from the server through a server connection or the manipulated file is restored to its original state.

In this case, a file in which the dummy variable is removed or a file whose operation is modified is restored to its original state may not be stored in the user computer, thereby preventing unauthorized copying of the software.

This can be prevented by running a program that prevents the storage of files that are restored to their original state when the software is required to be installed on the central server. The server checks whether the program is running correctly and provides services. .

In addition, if the number of installation of the program software is to be limited, the number of downloads of the matching file stored in the central server is limited, and in the case of the additional matching file that uses the permitted number of installations, the additional matching stored in the central server is used. If you delete a file, you can no longer use the file.

In addition, since the software is supplied online, it is possible to provide the software free of charge for individual users by grasping the state of the computer used by the user through IP, etc. It may be.

In addition, in order to prevent unauthorized copying of program software, program software is divided into two or more parts, some of which are installed on an individual user's computer, and some of the remaining important algorithms are installed on a server. In other words, if you just order work online from your personal computer, you can perform the operation on the central server and provide the result back to your personal computer. In this case, if the data needs to be processed, raw data can be transferred from the personal computer used by the individual to the central server.

In addition, these days, a significant problem, such as the hacking of important documents, such as the various forms of documents created by individual workers to prevent the use of other people at the same time to encrypt or compress the file password or password If you want to protect your data by typing, the currently used method is the encrypted document file or the password input by the user who encrypted the compressed file, so that the authorized user can save the document file or compressed file later. And other encrypted files, when it is determined that the same password is compared with the input password, decryption is allowed to view the document or use the file.

However, since this method stores the password entered by the user in a file protected by a password, there is room for analyzing the file where the password is stored and finding out the portion corresponding to the password. It should be suggested that no password be stored.

To do this, in the process of saving the password, all the character values (number, Korean consonants, vowels, lowercase letters, uppercase letters, key values corresponding to the languages of other countries, special characters) that can be entered as passwords for the modification of the file Operation method for file transformation, etc.) must be defined in the software programming process.

Referring to FIG. 2 as an example, in the case of protecting a document written as "Korea," when a number of 1 is entered as a password, two letters are defined to be exchanged, and the number 2 is defined as a password. It is defined to exchange vowels by pairing two letters when entered, and if the number 3 is entered as a password, it is assumed to represent consonants and vowels separately.If the number 4 is entered as a password, it is paired four by one. Suppose you have programmed and defined to exchange the fourth and the second and the third and the third, and you want to protect the document by typing password 1234 to protect it by password-protecting the document written "Korea." If it is, the process of splitting and mixing the document as shown in 2_2 of Figure 2, and of course entered as a password For other characters, the file's transformations must be pre-defined and programmed.

At this time, when a person who is allowed to view the document enters 1234 as a password and hits enter, the data is converted in the form of restoring the modified file again by an operation corresponding to the predefined number 4. A decryption process for restoring data corresponding to 3, 2, and 1 is performed, and the document “Korea” is presented before encryption through the same process as that of 2_3j in FIG. 2.

However, if an incorrect password 2431 is entered, the order of restoring the file is not correct, and the data corresponding to the order of 2431 occurs, so that the correct document "South Korea" cannot be output.

This is explained only by the letters of the document, but because all the letters in the document are defined as numeric values, and all kinds of computer files, or all software, are represented as binary values in binary, mathematically or physically Modifications to the location will hinder the presentation of the correct document.

The features and advantages of this method are that the methods that have been used so far, even if they use a variety of techniques, store passwords entered by the user in a passworded file or document. When trying to release a file, there is a disadvantage that the possibility of hacking always exists because the input password is stored in the encrypted file for comparison with the input password. However, the method proposed through the present invention provides a password in the encrypted file. Is free from hacking because it is not stored.

In addition, even if a hacker or the like knows an algorithm for modifying a file used for encryption, since the algorithm itself is based on a character entered as a password, there is no obvious solution when the user does not know the password.

In addition, in case of an online book that requires a computer file to be provided to an individual user, this is an input password for modifying a file to prevent indiscriminate sharing of the provided file. You can create and service a file with different characteristics for each user. Also, in all cases where you want to use the file, some of the passwords are selected by the user and some are selected by the server to check the license. If you combine these services properly, you will not be able to restore files with passwords that only you know unless your server allows them.

In addition, regardless of the suitability of the password, the file is presented unconditionally after processing the file with the formula corresponding to the password.If the password is correct, a file such as a document is presented. The non-presentation method is that when a file such as a document is not presented, it is impossible to use a software that automatically generates a password by randomly generating a password and repeating the operation until the password is correct. It is difficult to find out whether the document itself is correct by inputting an incorrect password because the program itself needs to check whether it is available by directly executing the program file. It is not possible to attempt decryption using a letter combination automatically. In addition, since the document or file is presented for the input password without asking for the correctness of the password, the operator needs to check the accuracy of the document with the naked eye. Since the combination of keys corresponds to astronomical probabilities, it is functionally better.

However, the problem with this software encryption method is that even if a user who wants to use a software file, such as a document, enters a wrong password, the file is deformed and converted into an unusable file. To solve this problem, if you decompress the compressed file when you want to decompress the compressed file, the compressed file will be created as it is.

Therefore, even if you want to password protect the document in this way, the file extension may be different, and the encrypted file may be managed separately from the decrypted file.

In addition, in the web programming such as homepage production, various services are possible due to the development of various technologies, but when individual users want to create a homepage, it is difficult for individual users to acquire and use all the technologies.

Therefore, if all functions necessary for homepage production are provided in advance, and a user can simply use a mouse click or drag and drag a desired function, there is no need to learn various technologies.

Currently, the web page production technology is provided by this type, such as a zero board or an easy board, a method of providing a bulletin board, a login function, a recent post extraction function, and an easy board programming. Although it supports the creation of a more easy homepage using the contents, there are various difficulties to use easily because the contents such as environment setting for the use are complicated to learn, but the corresponding file is provided as a solution through the present invention. It has the advantage of being owned and managed directly.

However, the method to be proposed in the present invention is simple to use, so it can be operated in a general environment without installing or even installing simply, and it is optional to produce JavaScript or other programming parts necessary for website development in advance. If provided, the user can select the necessary function and input only the title of the part to be expressed or the information to be presented to perform the necessary function, thereby illegalizing programs of various programs (Dreamweaver, etc.) used as the homepage development toll. There is no need to duplicate it.

By using the skin function here, users can easily create and utilize any kind of homepage screen they want.

In a similar concept, there can be cafes of various sites. In this cafe, the appearance of the cafe is determined, and a function or screens selected by the user are selected and made in such a format.

In addition, since the source of the created cafe is not provided to the user, the user cannot connect to the domain purchased by the user, and has a disadvantage that only the site can be used for access.

Overall, some of the matching partitioned files are owned by individual users, while others are installed on the server by a mix of files owned by individuals and files on the server, but cannot be retrieved from the server. If you inevitably need to format the computer after purchasing and installing the software through the network, the ID and password to confirm the right to install the software among users by limiting the number of times that the computer can be reinstalled free of charge only once. Limiting the sharing of data, and verifying the address of a computer through a fixed or dynamic IP address assigned to a computer connected to the Internet. If you have a computer, you will be able to sell it for a fee. If a character or number is entered as a password, the file is modified according to the corresponding password value, and the password is changed by modifying it differently according to the order or number of the input passwords. It does not need to store passwords in a file, and on the contrary, the file is restored from the very end of the password, which is entered as a password. On the other hand, there is a characteristic that each equation to be transformed should be defined, and in the method of decrypting the password currently used, when the password is stored in the encrypted file and the password is entered for later decryption, Compare the passwords with each other when the password is incorrect. In order to prevent the program from being inputted by the user, instead of presenting a wrong message when the password is wrong, instead of presenting a wrong result file or document, it has a feature of preventing the program from automatically decrypting the program. By not providing all the algorithms to the user, but providing only the method of using the software, the use of the software is performed on the personal computer, the operation and the operation of the software are performed on the server, and only the result is presented. Hacker hacks important files on the server through the method of dividing one file into several files as shown in FIG. 3 and providing the correct file through a combination of them. Even if you took an important file, It has a feature that makes it impossible to use because it doesn't know the sum, and also protects a very important file so that when you want to password-protect this file, you can use the password algorithm itself to prevent hacking. As a service to the user without providing it to the user, in software sales, the password is developed for the developed software, and this file is provided to the individual user. It provides hanging passwords, but does not provide individual users with passwords, but rather provides them to the software automatically, so that the passwords are solved and run the software. And some of the rest come to If the user wants to use the file, the file can be used by combining the file on the server with the file owned by the individual user, without providing the user with the file on the server. Finally, in the homepage development, the board, JavaScript, or other programs necessary for the homepage development are prepared and provided to the users, and the user only selects the necessary functions. It inserts into its own homepage, and it has a characteristic feature that allows the file to be modified and used according to an individual's purpose by inserting only the information to be provided through its own homepage.

Also, to express your own homepage, select all the selected functions such as selected picture, javascript, flash, etc. with your mouse and move the location of the picture freely in Korean (hwp). If you can select and express various kinds of sources and change the size or move them freely, you won't need a long time to learn the skills necessary for homepage production.

In addition, in the case of DreamWeaver, which is currently provided as a homepage creation tool, it is composed of various difficult and complicated formats to determine and configure the format of the homepage screen. Comes with difficulty.

Therefore, if a homepage developer can freely control the size and position of a picture freely according to his or her taste through simple mouse operation, even a novice user will be able to access psychologically and technically more easily and stably.

That is, in the above, if the file creator alters or encrypts the file to generally protect the file, and allows the user to use the file to those who are suitable for use, the homepage production support method may include It is a way for users to modify their files to suit themselves and organize them according to the characteristics of the homepage, and to download, store, and manage the composed files.

In addition, in general, the bulletin board function necessary for homepage production is complicated and technically difficult for individual workers to program and develop.

In addition, it is difficult to program the most basic log-in function to check the user's access or limit the use of the homepage only to authorized users.

One of these features is the Zeroboard (Easyboard), which is weak in its program, and its database management function is particularly weak for managing its members. Follows.

And, even though it is true that the skin function used in these metaphors can easily change the existing difficult boards or login screens, in order to change them to suit the tastes of developers, it is necessary to go through the difficult task of making skins by themselves. .

However, the method proposed by the present patent may allow a personal homepage developer to work according to his or her aesthetic taste by modifying and modifying each part or each position of the login screen of the bulletin board or the login screen having an external login function. Will be.

In other words, homepage developers need to be able to draw their own pictures, download pictures or photos through web surfing, and cut them to a suitable size through a picture file management program (Photoshop, etc.).

If this idea is implemented, even if you're not a computer-savvy person, you'll have the ability to create a beautiful and sophisticated homepage, like a large commercial portal site, with just five minutes of manual reading.

The present invention has the following effects in the invention of encryption and prevention of unauthorized copying of software that has been used indiscriminately in the past.

Currently, when a lot of companies develop and distribute the software, illegal copies are released in just a few days, and the piracy of developers is weakened because of the illegal copying and the copying. The situation is reversed, inspiring developers to develop.

In addition, software developers can solve the problem of unauthorized copying of the software and secure a certain stable demand, thus freeing up more free users and lowering the price of the software to general users in order to be compensated by the enterprise. Since the basic framework that can be supplied is formed, users also have the effect of being able to use software cheaply.

Claims (8)

In order to protect a computer file, transforming the computer file to form a matching file using a matching partition, providing a primary matching file to the user, authenticating the user's permissions, and A method of preventing illegal copying of software, including remotely installing by installing only the installation file and allowing installation without storing additional matching files corresponding to the matching file on the user's computer. The method of claim 1, further comprising: dividing the important computer data files into a plurality of files by a predefined operation to prevent hacking, and storing them in the computer, and when dividing the corresponding data files divided to use the data files. Hacking prevention method comprising the step of restoring the file by performing the operation inverse of the operation so that the hacker can not use the file even if hacking Identifying the location of the computer attempting to install the software using IP to provide the software file over the network, determining the user's identity based on this, and determining whether to approve the software file installation based on the identity. Softway piracy prevention method comprising the steps of: In order to prevent unauthorized copying of the software in dividing the software, an interface program for providing an interface environment of the software for using the software, and an interface program for providing an interface environment by dividing it into a computing environment program are provided to the user. A computing program comprising a user connecting to a server where a computing program is installed through an interface environment program and requesting a computing work, and providing a result calculated to the user's interface program according to the user's request is provided to the user. Software piracy prevention method characterized in that not provided In order to allow users to modify the pre-produced source in order to support easy homepage production, the steps of pre-producing the source for the homepage production, the user selecting the source required for the homepage production, How to support the homepage production, comprising the step of modifying according to the user's own homepage characteristics In order to protect the computer file by modifying the computer file, the computer file is encrypted to prevent unauthorized use of the software by entering a password and a predefined formula according to each value entered as the password. Encryption method, characterized in that the password is not stored in the file comprising the step of modifying the computer file by processing In order to protect the computer files by modifying the computer files, to prevent the unauthorized use of the software by encrypting the computer file, the steps required to install the software online, the authentication step to verify the user's rights, and the password How to prevent unauthorized software copying, including supplying the software rather than the user In order to protect the software by the encryption method in which the password is stored in an encrypted computer file from hacking, to prevent the use of a program that automatically finds the password for the purpose of restoring the file protected as a password, the password is used to restore the file. Entering the password, comparing the password and the password stored in the software file, and restore the correct file if the password entered is correct, if the password is incorrect, the correct file instead of a message that the password is wrong Software protection method comprising the step of presenting a modified file rather than