WO2013020446A1

WO2013020446A1 - File encryption and decryption method, device and system

Info

Publication number: WO2013020446A1
Application number: PCT/CN2012/079005
Authority: WO
Inventors: 张健
Original assignee: 华为技术有限公司
Priority date: 2011-08-11
Filing date: 2012-07-23
Publication date: 2013-02-14
Also published as: CN102254127A

Abstract

Disclosed are a method, device and system for file encryption and decryption, related to the field of digital rights management and able to improve the efficiency of digital file encryption and decryption without requiring that the encryption device or decryption device has a large memory, able to present decrypted content during the process of digital file decryption, and to improve user experience. The method comprises: reading a starting length of file content from the beginning of an original file, and writing same into an encryption file; said starting length is the length from the beginning of the original file to the starting place where encrypted text and plain text is alternatingly encrypted; encrypting the file content after the starting length of the original file in a manner in which encrypted text and plain text alternate, and writing the encrypted file content into the encryption file. This solution is mainly used in processes of digital file encryption and decryption.

Description

Method, device and system for encrypting and decrypting files This application claims to be filed on August 11, 2011 with the Chinese Patent Office, application number 201110230148. 0, the Chinese patent entitled "File Encryption and Decryption Method, Device and System" Priority of the application, the entire contents of which are incorporated herein by reference. Technical field

The present invention relates to the field of digital rights management, and in particular, to a method, device and system for encrypting and decrypting files. Background technique

With the development of network and mobile communication technologies, the speed of digital file transmission has been greatly improved, and the way for users to obtain digital files has become simple and diverse. However, in the absence of effective copyright protection, digital files will be vulnerable to piracy, and copyright holders of digital files will lose the benefits they deserve. Therefore, the network communication of digital files needs to be effectively protected by Digital Rights Management (DRM). The basic working principle of DRM is: In the authorization center of digital files, that is, on the DRM server, Advanced Encryption Standard (AES) is applied to digital files and compressed; when users read digital files on the terminal , need to connect to the corresponding authorization center, and through the authorization and authorization of the authorization center, then AES decryption and reading of the digital file.

Currently, the commonly used DRM technology is: On the DRM server, the contents of the digital file are read into the memory as a whole, and then AES is encrypted and saved. When the terminal reads, the encrypted digital file is obtained from the server, and then the contents of the encrypted digital file are read into the memory as a whole, and AES decryption is performed.

In the process of implementing the encryption and decryption of the above file, the inventors found that at least the following problems exist in the prior art: Since the content of the digital file needs to be read into the memory as a whole for encryption and decryption, the memory of the DRM server and the terminal device The requirements are higher. Moreover, each byte in the entire digital file needs to be encrypted and decrypted, which takes a long time, and the larger the volume of the digital file, the longer the encryption and decryption takes. Summary of the invention

Embodiments of the present invention provide a method, an apparatus, and a system for encrypting and decrypting a file, which can improve the efficiency of encryption and decryption of a digital file, and do not require an encryption device or a decryption device to have a large memory, and can decrypt the digital file. Licensing presents the decrypted content to enhance the user experience.

In order to achieve the above object, the embodiment of the present invention adopts the following technical solutions:

A file encryption method, including:

The contents of the file of the starting length are read from the beginning of the original file and written into the encrypted file, wherein the starting length is the length from the beginning of the original file to the start position where the ciphertext and the plaintext are alternately encrypted;

The content of the file after the start length of the original file is encrypted in the form of alternating ciphertext and plaintext, and the encrypted file content is written into the encrypted file.

A method for decrypting a file, including:

The contents of the file of the start length are read from the beginning of the encrypted file and written into the decrypted file, wherein the initial length is the length from the beginning of the encrypted file to the start position where the ciphertext and the plaintext are alternately decrypted;

The content of the file after the start length of the encrypted file is decrypted in the form of alternating ciphertext and plaintext, and the decrypted file content is written into the decrypted file.

A file encryption device, comprising:

a starting encryption unit, configured to read a file content of a starting length from the beginning of the original file, and write the file to the encrypted file, where the starting length is a starting position from the beginning of the original file to the encryption of the ciphertext and the plaintext alternately Length between

The alternate encryption unit is configured to encrypt the content of the file after the start length of the original file in an alternating manner between the ciphertext and the plaintext, and write the encrypted file content into the encrypted file.

A file decryption device, comprising:

The initial decryption unit is configured to read the content of the starting length from the beginning of the encrypted file and write the decrypted file, wherein the initial length is from the beginning of the encrypted file to the ciphertext and the plaintext. The length between the starting positions of the line decryption;

The alternate decryption unit is configured to decrypt the content of the file after the start length of the encrypted file in an alternating manner between the ciphertext and the plaintext, and write the decrypted file content into the decrypted file.

A file encryption and decryption system comprising: an encryption device and a decryption device.

The method, device and system for encrypting and decrypting a file according to an embodiment of the present invention, when encrypting, segmenting an original file into a memory according to a predetermined plaintext length and a ciphertext length for encryption processing, which is original in the prior art. Compared with the method in which the file is read into the memory for encryption, the memory requirement of the encryption device is low. Moreover, the encryption and decryption are performed in a form in which the ciphertext and the plaintext are spaced apart from each other, and the amount of data that needs to be encrypted and decrypted is reduced as compared with the prior art method of encrypting and decrypting each byte in the original file. , can improve the efficiency of encryption and decryption. Moreover, in the form of discontinuous encryption and decryption, compared with the prior art method of encrypting and decrypting the original file as a whole, the decrypted content can be presented in the process of decryption, and the decryption is performed while reading. Thereby reducing the time for the user to wait for a response, and improving the user experience. DRAWINGS

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the embodiments or the description of the prior art will be briefly described below. Obviously, the drawings in the following description are only It is a certain embodiment of the present invention, and other drawings can be obtained from those skilled in the art without any creative work.

1 is a flowchart of a method for encrypting a file in Embodiment 1 of the present invention;

2 is a flowchart of a method for decrypting a file in Embodiment 1 of the present invention;

3 is a flowchart of a method for encrypting a file in Embodiment 2 of the present invention;

4 is a flowchart of a method for decrypting a file in Embodiment 2 of the present invention;

5 is a schematic diagram of a composition of an encryption device for a file according to Embodiment 3 of the present invention; FIG. 6 is a schematic diagram of a composition of an encryption device for another file according to Embodiment 3 of the present invention; Schematic diagram of the composition of the encryption device of the file; 8 is a schematic diagram of a composition of an encryption device for another file according to Embodiment 3 of the present invention; FIG. 9 is a schematic diagram of a composition of an encryption device for another file according to Embodiment 3 of the present invention; FIG. 11 is a schematic diagram of the composition of another file decryption apparatus according to Embodiment 3 of the present invention; FIG. 12 is a schematic diagram of the composition of another file decryption apparatus according to Embodiment 3 of the present invention; 13 is a schematic diagram of a composition of a decryption apparatus for another file in Embodiment 3 of the present invention; FIG. 14 is a schematic diagram showing the composition of a file encryption and decryption system according to Embodiment 3 of the present invention. detailed description

The technical solutions in the embodiments of the present invention are clearly and completely described in the following with reference to the accompanying drawings in the embodiments of the present invention. It is obvious that the described embodiments are only a part of the embodiments of the present invention, but not all of the embodiments. All other embodiments obtained by a person of ordinary skill in the art based on the embodiments of the present invention without creative efforts are within the scope of the present invention.

Example 1

An embodiment of the present invention provides a file encryption method, as shown in FIG. 1 , including:

101. The encryption device reads the content of the starting length from the beginning of the original file and writes the file into the encrypted file, where the starting length is between the beginning of the original file and the starting position of the encryption between the ciphertext and the plaintext. length.

Wherein, according to the predetermined starting length value, the content of the file of the starting length is read from the beginning of the original file, and the encrypted file is written in the form of plaintext, so as to identify the starting position where the ciphertext and the plaintext are alternately encrypted. The starting length is the length from the beginning of the original file to the starting position where the ciphertext and the plaintext are alternately encrypted. The content of the file after the start length of the original file, that is, the content after the start position, is encrypted in the form of alternating ciphertext and plaintext.

102. The encryption device encrypts the content of the file after the start length of the original file in an alternating manner between the ciphertext and the plaintext, and writes the encrypted file content into the encrypted file.

Wherein, the content of the file after the start length of the original file is encrypted according to the ciphertext and the plaintext, and the method of writing the encrypted file content into the encrypted file may be first The form of the ciphertext after the ciphertext may also be in the form of the ciphertext after the ciphertext. The specific embodiment of the present invention does not limit this.

When the form of the first ciphertext is used, the method is specifically: reading the encrypted file content, encrypting the encrypted file content, and writing the encrypted file content into the encrypted file; After the length of the file content, the file content of the read plain length is written into the encrypted file; the content of the file after the start length of the original file is repeatedly read as described above until the original file is encrypted.

When the ciphertext of the first plaintext is used, the method is specifically: writing the file content of the plaintext length into the encrypted file; after reading the file content of the plaintext length, reading the encrypted length of the file content, and encrypting The length of the file content is encrypted, and the encrypted file content is written into the encrypted file; according to the above steps, the content of the file after the start length of the original file is repeatedly read until the original file is encrypted.

An embodiment of the present invention provides a method for decrypting a file, as shown in FIG. 2, including:

201. The decryption device reads the file content of the start length from the beginning of the encrypted file, and writes the file content into the decrypted file, where the initial length is the length from the beginning of the encrypted file to the start position where the ciphertext and the plaintext are alternately decrypted. .

Wherein, the beginning of the encrypted file is a file content that does not include other parameter information such as a file header. If a file header is added to the encryption of the original file, it is necessary to remove the file header before the decryption starts, according to a predetermined starting length value. The contents of the file whose initial length is read from the official content of the encrypted file are written into the decrypted file to identify the starting position where the ciphertext and the plaintext are alternately decrypted. The content before the start position, that is, the file content of the read start length, is in plain text and can be written into the decrypted file without performing a decryption operation. It should be noted that the decrypted file is only accessed in the memory, and the corresponding decrypted file is not generated on the disk of the decryption device, so that the original file content obtained by the decryption can be effectively copyright protected.

202. The decryption device decrypts the file content after the start length of the encrypted file in an alternating manner between the ciphertext and the plaintext, and writes the decrypted file content into the decrypted file.

Wherein, depending on the encryption rules, the method of reading the encrypted file used during decryption is not Similarly, the content of the file after the start length of the encrypted file is decrypted in the form of alternating ciphertext and plaintext, and the method of writing the decrypted file content into the decrypted file is specifically as follows:

When the encryption rule adopts the form of alternating the plaintext and the plaintext, the file content of the encrypted length is first read in the decryption, and the content of the encrypted length is decrypted, and the decrypted file content is written. Decrypt the file; after reading the encrypted file content, read the file content of the plain text length and write it to the decrypted file; repeatedly read the file content after the start length of the encrypted file according to the above steps until the current decrypted file is decrypted The zone decryption is complete.

When the encryption rule adopts the form in which the ciphertext is alternated after the plaintext, the file content of the plaintext length first read in the decryption file is written into the decrypted file; after reading the file content of the plaintext length, the encryption is read. The length of the file content, and decrypt the encrypted file content, and write the decrypted file content into the decrypted file; follow the above steps to repeatedly read the file content after the start length of the encrypted file until the current decrypted area of the encrypted file The decryption is complete.

The encryption and decryption method of the file provided by the embodiment of the present invention reads the original file segment into the memory according to the predetermined plaintext length and the ciphertext length for encryption processing during encryption, and reads the original file as a whole in the prior art. Compared to the method of encrypting memory, the memory requirements of the encryption device are lower. Moreover, the encryption and decryption are performed in a form in which the ciphertext and the plaintext are spaced apart from each other, and the amount of data that needs to be encrypted and decrypted is reduced as compared with the prior art method of encrypting and decrypting each byte in the original file. , can improve the efficiency of encryption and decryption. Moreover, in the form of discontinuous encryption and decryption, compared with the prior art method of encrypting and decrypting the original file as a whole, the decrypted content can be presented in the process of decryption, and the decryption is performed while reading. Thereby reducing the time for the user to wait for a response, and improving the user experience.

Example 2

The embodiment of the invention provides a method for encrypting and decrypting a file, and the digital file is interval-encrypted on the encryption device to obtain an encrypted file capable of effectively protecting the copyright of the digital file; when the decryption device issues a request for obtaining the encrypted file to the encryption device The encryption device transmits the encrypted file to the decryption device; the decryption device performs corresponding interval decryption, and displays the decrypted digital file. Specifically, the encryption method of the file is as shown in FIG. 3, including:

301. The encryption device determines a start length, an encryption length, and a plaintext length according to the size of the original file.

The start length, encryption length, and plaintext length are predefined attribute values, which can be set as needed. According to the size of the original file, the starting length, the encryption length, and the plaintext length are determined, so as to adjust the relative proportion of the ciphertext and the plaintext in the encrypted file, and the efficiency of the encryption is controlled. For example, when the original file is less than 512 Kbytes, the plaintext length is determined to be 0 bytes, so that the ciphertext ratio is 100%; when the original file size is between 512 Kbytes and 1024 Kbytes, the plaintext length is determined to be 16 bytes, The ciphertext ratio is about 50%. When the original file is larger than 1024Kbytes, the plaintext length is determined to be 16x9 bytes, so that the ciphertext ratio is about 10%.

It should be noted that other predetermined rules may also be used for the start length, the encryption length, and the plaintext length. For example, the ciphertext length is set to be sequentially incremented, and the plaintext length is set to a descending form, and a dynamically varying length value is obtained in the encryption process. If the plaintext length and the ciphertext length are calculated according to a predetermined rule, the calculation rule of each length value needs to be described in the encryption rule, so that the decryption device obtains the corresponding plaintext length and ciphertext length when decrypting.

Among them, in some encryption algorithms, the length of the content to be encrypted is fixed, so the encryption length must be a multiple of the encryption base value in the encryption algorithm. For example, in the AES 128-CBC algorithm, the length of the encrypted block is fixed to 128b its each time, that is, 16 bytes, so when defining the encryption length, the encryption length must be a multiple of 16 bytes in order to satisfy AES128- CBC encryption algorithm. The encryption algorithm used in the embodiment of the present invention includes but is not limited to the above algorithm, and may also be other symmetric encryption algorithms such as AES192-CBC, AES256-CBC.

302. The encryption device sends the start length, the encryption length, the plaintext length, and the encryption rule to the decryption device of the file.

The method for the encryption device to send the start length, the encryption length, the plaintext length, and the encryption rule to the decryption device of the file may be: The encryption device adds a file header at the beginning of the encrypted file, and sets the start length, the encryption length, and the plaintext length. And the encryption rule is written in the file header of the encrypted file in the form of name-va lue, so that the encrypted information is sent to the file along with the encrypted file. Decryption device. The method for the encryption device to send the start length, the encryption length, the plaintext length, and the encryption rule to the decryption device of the file may also be: The encryption device encapsulates the start length, the encryption length, the plaintext length, and the encryption rule into the cell and sends the file to the file. Decryption device.

It should be noted that when the start length, the encryption length, and the plaintext length are calculated according to a predetermined rule, the encryption length and the plaintext length in an encrypted file are not fixed, so the start length needs to be described in the encryption rule. The encryption length and the calculation rule of the plaintext length, so that the decryption device obtains the corresponding length value when decrypting.

Further, if the encryption device and the decryption device have previously agreed on the start length, the encryption length, the plaintext length, and the encryption rule, the encryption device may not need to transmit the encrypted information to the decryption device again.

303. The encryption device reads the content of the file of the start length from the beginning of the original file, and writes the file content into the encrypted file.

Wherein, the starting length is the length from the beginning of the original file to the start position where the ciphertext and the plaintext are alternately encrypted, and the file content of the starting length is read from the beginning of the original file according to the predetermined starting length value. The encrypted file is written in plaintext so that the encryption device and the decryption device recognize the start position where the ciphertext and the plaintext are alternately encrypted. The content of the file after the start length of the original file, that is, the content after the start position, is encrypted in the form of alternating ciphertext and plaintext.

304. The encryption device reads the encrypted file content, encrypts the encrypted file content, and writes the encrypted file content into the encrypted file.

Wherein, in step 303, the encryption device obtains a starting position where the ciphertext and the plaintext are alternately encrypted, and the file content of the encrypted length is sequentially read from the starting position for encryption, and the encrypted file content is written into the encrypted file. .

In addition, in the process of performing encryption in the ciphertext and the plaintext, the first plaintext or the first ciphertext may be used, which is not limited in this embodiment. When the alternate encryption is performed in the form of the first plaintext ciphertext, the steps 304 and 305 are reversed, and the encryption rule is written to the file header or transparently transmitted to the decryption device by the cell. 305. The encryption device reads the file content of the plaintext length and writes the file content into the encrypted file.

The file content of the plaintext length read by the encryption device is not required to be encrypted, and is written in the encrypted file in the form of plaintext, and the encrypted content is separated by the plaintext content.

306. The encryption device determines whether the original file has been read. If the original file has not been read, step 304 is performed. If the original file has been read, step 307 is performed.

Wherein, before the original file encryption is completed, steps 305 and 306 are repeatedly performed alternately, and the original file is sequentially read until the original file is encrypted.

307, the encryption device determines whether the last file content in the original file should be written in the form of cipher text; if the last file content in the original file should not be written in the form of cipher text, step 308; The last file content in the original file should be written to the encrypted file in the form of cipher text, and then step 309 is performed.

The original file size may be in cipher text or in plain text because the size of the original file is different, and the starting length, encryption length, plaintext length, and encryption rules are different. The specific method for determining whether the last file content in the original file should be written into the encrypted file in cipher text may be: When the last file content in the original file is read, whether the content of the previous file according to the current content is plain text or confidential The text determines the form in which the current file content is written to the encrypted file. If the content of the previous paragraph is written to the encrypted file in clear text, the current content should be written to the encrypted file in cipher text; if the content of the previous paragraph is written in encrypted form, the current content should be in clear text. The form is written to an encrypted file.

308. The encryption device directly writes the last file content in the original file to the encrypted file in clear text.

Among them, the plaintext content does not need to be encrypted, and there is no requirement for the content length, and the encrypted text is directly written in the form of plaintext.

309, the encryption device determines whether the length of the last file content in the original file reaches a base value; if the length of the last file content in the original file does not reach the base value, step 310 is performed; if the length of the last file content in the original file reaches The base value is then executed in step 311.

Among them, in some encryption algorithms, the length of the content to be encrypted is fixed, so The length of the content to be encrypted, that is, the length of the last content in the original file must reach the encryption base value in the encryption algorithm, or a multiple of the base value. For example, in the AES128-CBC algorithm, the length of the encrypted block is fixed to 128b itself, that is, 16 bytes, each time the encryption is performed, so the length of the content to be encrypted must be a multiple of 16 bytes, if the last file content is less than 16 words. If the section is not a multiple of 16 bytes, it needs to be complemented to a multiple of 16 bytes or 16 bytes in order to satisfy the AES 128-CBC encryption algorithm.

31 0. The encryption device supplements the last file content so that the length of the last file content reaches the base value.

In order to meet the requirements of the encryption algorithm for the length of the encrypted content, the final file content is supplemented so that the length of the last file content reaches the base value of the encryption in the encryption algorithm, or a multiple of the base value. If the file content is complemented during encryption, the corresponding content will also be deleted when decrypting.

31 1. The encryption device encrypts the last file content or the supplemented file content and writes it to the encrypted file.

The embodiment of the present invention provides a file decryption method as shown in FIG. 4, which includes:

401. The decryption device acquires a start length, an encryption length, a plaintext length, and an encryption rule. The method for obtaining the start length, the encryption length, the plaintext length, and the encryption rule by the decryption device may be: the decryption device reads the start length, the encryption length, the plaintext length, and the encryption rule from the file header; or receives the carried by the encryption device. The starting length, the encryption length, the plaintext length, and the cells of the encryption rule, and decrypting therefrom to obtain the starting length, the encryption length, the plaintext length, and the encryption rule; or the start length, the encryption length, and the plaintext length are pre-agreed by both the encryption and the decryption parties. And encryption rules.

402. The decryption device reads the file content of the start length from the beginning of the encrypted file, and writes the file content into the decrypted file.

And, according to the predetermined starting length value, the file content of the start length is read from the beginning of the encrypted file and written into the decrypted file, so as to identify the starting position of the ciphertext and the plaintext alternately decrypted. It should be noted that the decrypted file is only accessed in the memory, and is not generated on the disk of the decryption device. Corresponding decryption files, so that the original file content obtained by decryption can be effectively copyright protected.

403. The decryption device reads the encrypted file content, decrypts the encrypted file content, and writes the decrypted file content into the decrypted file.

Wherein, in step 402, the starting position of the ciphertext and the plaintext are decrypted alternately, and the file content of the encrypted length is sequentially read from the starting position for decryption, and the decrypted file content is written into the decrypted file.

Wherein, according to the sequential encryption in the step 304 and the step 305, the ciphertext and the plaintext are different in sequence, and the manner of reading the encrypted file used in the decryption is different, and the content of the file after the start length of the encrypted file is in accordance with the ciphertext. The method of decrypting in the form of alternating with the plaintext, and writing the decrypted file content into the decrypted file may be: when the encryption rule adopts the form of alternating the plaintext after the first ciphertext, and correspondingly when decrypting Step 403 is performed first, and then step 404 is performed. When the encryption rule is in the form of alternating the ciphertext after the plaintext, the step 404 is performed first in the decryption, and then the step 403 is performed.

404. The decryption device reads the file content of the plaintext length and writes the file content into the decrypted file.

The file content of the read plain text length is not encrypted, and the corresponding file content in the original file can be directly obtained, and directly written into the decrypted file.

405. The decryption device determines whether the current decrypted area of the encrypted file has been read. If the current decrypted area of the encrypted file is not read, step 403 is performed. If the current decrypted area of the encrypted file has been read, step 406 is performed. .

Wherein, before the decryption of the encrypted file is completed, steps 403 and 404 are repeatedly performed alternately, and the encrypted file is sequentially read until the decrypted area of the encrypted file is decrypted. It should be noted that the decryption area is a predetermined value on the decryption device, and the decryption area size can be adjusted according to the memory condition of the decryption device and actual needs. Therefore, only the file content corresponding to the current decrypted area is decrypted in the memory, instead of decrypting the entire encrypted file, which can effectively reduce the memory consumption. For example, when decrypting an e-book, if the decryption device has sufficient memory, the decryption area can be set as the entire file content, and part of the contents of the e-book can be displayed simultaneously, and the remaining file contents are all Decryption. If the decryption device has limited memory, the decryption area can be set to the first three pages of the current page to the last three pages of the current page, and only the file content in the current decryption area is decrypted in the memory.

406. The decryption device displays the content of the decrypted file.

407. The decryption device deletes the content of the file in the decrypted file that does not belong to the current decrypted area. In order to reduce the memory occupied by the decryption device, the content of the file that does not belong to the current decryption area may be deleted. For example, when decrypting an e-book, 4 sets the encrypted area to 7 pages and the current page to the 4th page. If the currently displayed page moves to the next page (page 5), the file content of the first page in the file is decrypted. Already does not belong to the current decryption area, 删除 delete the contents of the first page of the file.

The method for encrypting and decrypting a file provided by the embodiment of the present invention, the method, device and system for encrypting and decrypting a file according to an embodiment of the present invention, when the encryption is performed, the original file is segmentally read according to a predetermined plaintext length and a ciphertext length. The encryption process is performed in the memory, and the memory requirement of the encryption device is lower than that of the prior art method of reading the original file into the memory for encryption. Moreover, the encryption and decryption are performed in a form in which the ciphertext and the plaintext are spaced apart from each other, and the amount of data that needs to be encrypted and decrypted is reduced as compared with the prior art method of encrypting and decrypting each byte in the original file. , can improve the efficiency of encryption and decryption. Moreover, in the form of discontinuous encryption and decryption, compared with the prior art method of encrypting and decrypting the original file as a whole, the decrypted content can be presented in the process of decryption, and the decryption is performed while reading. Thereby reducing the time for the user to wait for a response, and improving the user experience. Moreover, when decrypting, the size of the decrypted area can be set according to requirements, and the file content that does not belong to the current decrypted area is deleted in time. In the prior art, the encrypted file is read into the memory as a whole and decrypted, and the whole decryption is obtained in the memory. Compared with files, it can effectively save memory resources and reduce the memory requirements of the decryption device.

Example 3

The embodiment of the present invention provides a file encryption device. As shown in FIG. 5, the device includes: an initial encryption unit 51 and an alternate encryption unit 52.

The initial encryption unit 51 is configured to read the file content of the start length from the beginning of the original file and write the file into the encrypted file, where the starting length is from the beginning of the original file to the ciphertext and the plaintext. The length between the starting positions for encryption.

The alternate encryption unit 52 is configured to encrypt the content of the file after the start length of the original file in an alternating manner between the ciphertext and the plaintext, and write the encrypted file content into the encrypted file.

Further, as shown in FIG. 6, the alternate encryption unit 52 includes: a ciphertext writing module 521, a plaintext writing module 522, and a first repeating module 523.

The ciphertext writing module 521 is configured to read the encrypted file content, encrypt the encrypted file content, and write the encrypted file content into the encrypted file.

The plaintext writing module 522 is configured to read the file content of the encrypted length after the ciphertext writing module 521 reads the file content of the encrypted length, and write the file content of the plaintext length into the encrypted file.

The first repeating module 523 is configured to repeatedly start the ciphertext writing module 521 and the plaintext writing module 522 alternately until the original file is encrypted.

The plaintext writing module 522 is further configured to: write the file content of the plaintext length into the encrypted file. The ciphertext writing module 521 is further configured to: after the plaintext writing module 522 reads the file content of the plaintext length and write the file content into the encrypted file, read the file content of the encrypted length, and encrypt the encrypted file content, and encrypt the file content. The contents of the file are written to the encrypted file.

The first repeating module 523 is further configured to repeatedly alternately start the plaintext writing module 522 and the ciphertext writing module 521 until the original file is encrypted.

Further, as shown in FIG. 7, the alternate encryption unit 52 further includes: a determination module 524 and a supplementary module 525.

The determining module 524 is configured to determine whether the last file content in the original file should be written into the encrypted file in the form of cipher text.

The plaintext writing module 522 is further configured to directly write the last file content in the original file to the encrypted file in plaintext when the last file content in the original file is not written in the cipher text.

The supplementing module 525 is configured to determine whether the length of the last file content in the original file reaches a base value when the last file content in the original file is written in the cipher text, if the last file content in the original file If the length does not reach the base value, the final file content will be entered. Line complement, so that the length of the final file content reaches the base value.

The ciphertext writing module 521 is also used to encrypt the encrypted file content and write the encrypted file.

Further, as shown in FIG. 8, the encryption device of the file further includes: a determining unit 53 and a sending unit 54.

The determining unit 53 is configured to read the file content of the start length from the beginning of the original file at the initial encryption unit 51, and determine the start length, the encryption length, and the plaintext length according to the size of the original file before writing to the encrypted file.

The transmitting unit 54 is configured to decrypt the start length, the encryption length, the plaintext length, and the encryption rule to the file.

The sending unit 54 is further configured to add a file header at the beginning of the encrypted file, and write the attributes of the start length, the encryption length, and the plaintext length into the file header of the encrypted file.

The sending unit 54 is further configured to encapsulate the start length, the encryption length, the plaintext length, and the encryption rule into a decryption device that is sent to the file in the cell.

Further, as shown in FIG. 9, the alternate encryption unit 52 further includes: a first calculation module 526. The first calculating module 526 is configured to calculate the encryption length and the plaintext length according to a predetermined encryption rule in the process of encrypting according to the ciphertext and the plaintext, to obtain a dynamically changing encryption length and a plaintext length.

It should be noted that other descriptions of the partial functional modules in the embodiments of the present invention may refer to the corresponding content in the first embodiment and the second embodiment, and the embodiments of the present invention are not described herein again.

An embodiment of the present invention provides a file decryption apparatus. As shown in FIG. 10, the apparatus includes: an initial decryption unit 61 and an alternate decryption unit 62.

The initial decryption unit 61 is configured to read the file content of the start length from the beginning of the encrypted file, and write the file content into the decrypted file, wherein the initial length is a starting position from the beginning of the encrypted file to the ciphertext and the plaintext alternately decrypted. The length between.

The alternate decryption unit 62 is configured to decrypt the file content after the start length of the encrypted file in an alternating manner between the ciphertext and the plaintext, and write the decrypted file content into the decrypted file. Further, as shown in FIG. 11, the alternate decryption unit 62 includes: a ciphertext reading module 621, a plaintext reading module 622, and a second repeating module 623.

The ciphertext reading module 621 is configured to: when the encryption rule adopts the form of alternating ciphertext and the plaintext, read the file content of the encrypted length, and decrypt the encrypted file content, and decrypt the decrypted file content. Write to the decrypted file.

The plaintext reading module 622 is configured to read the file content of the plaintext length after the ciphertext reading module 621 reads the file content of the encrypted length, and write the file content into the decrypted file.

The second repeating module 623 is configured to repeatedly start the ciphertext reading module 621 and the plaintext reading module 622 until the current decrypted area of the encrypted file is decrypted.

The plaintext reading module 622 is further configured to: when the encryption rule adopts a form in which the ciphertext is alternated after the plaintext, the file content of the plaintext length is read and written into the decrypted file.

The ciphertext reading module 621 is further configured to: after the plaintext reading module 622 reads the file content of the plaintext length, read the file content of the encrypted length, decrypt the encrypted file content, and write the decrypted file content. Into the decrypted file.

The second repeating module 623 is further configured to repeatedly start the plaintext reading module 622 and the ciphertext reading module 621 until the current decrypted area of the encrypted file is decrypted.

Further, as shown in FIG. 12, the decryption apparatus of the file further includes: an obtaining unit 63, a display unit 64, and a deleting unit 65.

The obtaining unit 63 is configured to read the file content of the start length from the beginning of the encrypted file at the start decryption unit 61, and obtain the start length, the encryption length, the plaintext length, and the encryption rule before writing the decrypted file.

The display unit 64 is configured to display the content of the decrypted file.

The deleting unit 65 is configured to delete the content of the file in the decrypted file that does not belong to the current decrypted area. Further, as shown in FIG. 13, the alternate decryption unit 62 further includes: a second calculation module 624. The second calculating module 624 is configured to calculate the encryption length and the plaintext length according to the encryption rule in the process of decrypting according to the ciphertext and the plaintext, to obtain the dynamically changing encryption length and the plaintext length. It should be noted that other descriptions of the partial functional modules in the embodiments of the present invention may be referred to the corresponding content in the first embodiment and the second embodiment, and details are not described herein again.

The embodiment of the present invention provides a file encryption and decryption system, as shown in FIG. 14, comprising: an encryption device 71 and a decryption device 72.

The encryption device 71 is configured to read the file content of the start length from the beginning of the original file, and write the file content into the encrypted file; and encrypt the file content after the start length of the original file according to the ciphertext and the plaintext. Write the encrypted file contents to an encrypted file.

The decryption device 72 is configured to read the file content of the start length from the beginning of the encrypted file, and write the file content into the decrypted file; and decrypt the file content after the start length of the encrypted file in an alternating manner between the ciphertext and the plaintext. Write the decrypted file content to the decrypted file.

The digital file is interval-encrypted on the encryption device 71 to obtain an encrypted file capable of effectively protecting the copyright of the digital file. When the decryption device 72 issues a request for obtaining the encrypted file to the encryption device 71, the encryption device 71 transmits the encrypted file to the decryption device 72, and the decryption device 72 performs the corresponding interval decryption, and displays the decrypted digital file.

It should be noted that, for other descriptions of the function modules included in the encryption and decryption system of the file provided by the embodiment of the present invention, reference may be made to the descriptions of the corresponding device parts in Embodiment 1 and Embodiment 2 and Embodiment 3. It will not be repeated here.

The method and system for encrypting and decrypting a file according to an embodiment of the present invention, the method, device and system for encrypting and decrypting a file according to an embodiment of the present invention, segmenting an original file according to a predetermined plaintext length and a ciphertext length during encryption The encryption process is taken in the memory, and the memory requirement of the encryption device is lower than that of the prior art method of reading the original file into the memory for encryption. Moreover, the encryption and decryption are performed in a form in which the ciphertext and the plaintext are spaced apart from each other, and the amount of data that needs to be encrypted and decrypted is reduced as compared with the prior art method of encrypting and decrypting each byte in the original file. , can improve the efficiency of encryption and decryption. Moreover, in the form of discontinuous encryption and decryption, compared with the prior art method of encrypting and decrypting the original file as a whole, the decrypted content can be presented in the process of decryption, and the decryption is performed while reading. Thereby reducing the time for the user to wait for a response, and improving the user experience. And, when decrypting The size of the decryption area is set as needed, and the file content that does not belong to the current decryption area is deleted in time, and the encrypted file is read into the memory as a whole and decrypted in the prior art, and the entire decrypted file is obtained in the memory. Effectively save memory resources and reduce memory requirements for the decryption device.

Through the description of the above embodiments, those skilled in the art can clearly understand that the present invention can be implemented by means of software plus necessary general hardware, and of course, by hardware, but in many cases, the former is a better implementation. . Based on such understanding, the technical solution of the present invention, which is essential or contributes to the prior art, may be embodied in the form of a software product stored in a readable storage medium, such as a floppy disk of a computer. A hard disk or optical disk, etc., includes instructions for causing a computer device (which may be a personal computer, server, or network device, etc.) to perform the methods provided by various embodiments of the present invention.

The above is only a specific embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention. It is intended to be covered by the scope of the invention. Therefore, the scope of the invention should be determined by the scope of the claims.

Claims

Rights request

A method for encrypting a file, comprising:

Reading the file content of the start length from the beginning of the original file, and writing the file to the encrypted file, wherein the start length is between the beginning of the original file and the start position where the ciphertext and the plaintext are alternately encrypted. Length

The method for encrypting a file according to claim 1, wherein the content of the file after the start length of the original file is encrypted according to an alternating form of ciphertext and plaintext, and the encrypted file is encrypted. Writing the contents of the file to the encrypted file includes:

Reading the encrypted length of the file content, encrypting the encrypted length of the file content, and writing the encrypted file content into the encrypted file; after reading the encrypted length of the file content, reading the plaintext length Writing the file content into the encrypted file; repeatedly reading the file content after the start length of the original file according to the above steps until the original file is encrypted; or

Reading the file content of the plain text length into the encrypted file; after reading the file content of the plain text length, reading the file content of the encrypted length, and encrypting the file content of the encrypted length, after encrypting The file content is written into the encrypted file; the file content after the start length of the original file is repeatedly read according to the above steps until the original file is encrypted.

The method for encrypting a file according to claim 2, wherein the repeatedly reading the file content after the start length of the original file according to the above-mentioned steps until the original file is encrypted is completed, and further comprising:

Determining whether the last file content in the original file should be written into the encrypted file in the form of cipher text;

If the last file content in the original file should not be written in the cipher text, the last file content in the original file is directly written into the encryption in the form of plaintext. Document

If the last file content in the original file should be written into the encrypted file in the form of cipher text, it is determined whether the length of the last file content in the original file reaches a base value, if the last file in the original file If the length of the content does not reach the base value, the last file content is supplemented so that the length of the last file content reaches the base value, and the supplemented file content is encrypted and written into the encrypted file. .

The method for encrypting a file according to any one of claims 1 to 3, wherein the file content of the start length is read from the beginning of the original file, and before being written into the encrypted file, Includes:

Determining, according to the size of the original file, the start length, the encryption length, and the plaintext length;

The start length, the encryption length, the plaintext length, and the encryption rule are transmitted to the decryption device of the file.

The method for encrypting a file according to any one of claims 1 to 3, wherein the file content after the initial length of the original file is encrypted according to an alternating form of ciphertext and plaintext. The method includes: calculating, according to a predetermined encryption rule, the encryption length and the plaintext length in a process of performing encryption according to an alternating ciphertext and a plaintext, to obtain a dynamically changing encryption length and a plaintext length.

The method for encrypting a file according to claim 4, wherein the decrypting means for transmitting the start length, the encryption length, the plaintext length, and the encryption rule to the file includes:

Adding a file header at the beginning of the encrypted file, and writing the start length, the encryption length, the plaintext length, and an encryption rule to a decryption device sent to the file in a file header of the encrypted file ; or

The start length, the encryption length, the plaintext length, and the encryption rule are encapsulated into a decryption device that is sent to the file in the cell.

7. A method for decrypting a file, comprising: Reading the file content of the start length from the beginning of the encrypted file, and writing the decrypted file, wherein the initial length is the length from the beginning of the encrypted file to the start position where the ciphertext and the plaintext are alternately decrypted. ;

The method for decrypting a file according to claim 7, wherein the file content after the start length of the encrypted file is decrypted according to an alternating form of ciphertext and plaintext, and the decrypted Writing the contents of the file to the decrypted file includes:

When the encryption rule adopts the form of alternating the plaintext and the plaintext, the file content of the encrypted length is read, and the file content of the encrypted length is decrypted, and the decrypted file content is written into the decrypted file. After reading the encrypted file content, reading the file content of the plain text length and writing the file to the decrypted file; repeatedly reading the file content after the start length of the encrypted file according to the above steps until the The decryption of the current decryption area of the encrypted file is completed;

When the encryption rule adopts a form in which the ciphertext is alternated after the plaintext, the file content of the plaintext length is written into the decrypted file; after the file content of the plaintext length is read, the file of the encrypted length is read. Content, decrypting the encrypted length of the file content, and writing the decrypted file content into the decrypted file; repeatedly reading the file content after the start length of the encrypted file according to the above steps until the encryption is performed The current decryption area of the file is decrypted.

The method for decrypting a file according to claim 8, wherein before the reading of the file content of the start length from the beginning of the encrypted file, before writing to the decrypted file, the method further comprises: acquiring the start Length, the length of the encryption, the length of the plaintext, and the encryption rules.

The method for decrypting a file according to claim 8, wherein the decrypting the file content after the start length of the encrypted file according to the ciphertext and the plaintext alternately includes: In the process of decrypting the text and the plaintext, the encryption length and the plaintext length are calculated according to the encryption rule, and the dynamically changed encryption length and the plaintext length are obtained.

The method for decrypting a file according to any one of claims 7 to 10, further comprising: displaying the content of the decrypted file.

The method for decrypting a file according to claim 11, further comprising: deleting a file content of the decrypted file that does not belong to the current decrypted area.

1 3, a file encryption device, comprising:

a starting encryption unit, configured to read a file content of a starting length from a beginning of the original file, and write the file to the encrypted file, wherein the starting length is alternately encrypted from the beginning of the original file to the ciphertext and the plaintext. The length between the starting positions; the ciphertext and the plaintext are alternately encrypted, and the encrypted file contents are written into the encrypted file.

The encryption device for a file according to claim 13, wherein the alternate encryption unit comprises:

a cipher text writing module, configured to read the file content of the encrypted length, encrypt the file content of the encrypted length, and write the encrypted file content into the encrypted file;

a plaintext writing module, configured to: after the ciphertext writing module reads the encrypted length of the file content, write the file content of the plaintext length into the encrypted file;

And a first repeating module, configured to repeatedly start the ciphertext writing module and the plaintext writing module alternately until the original file is encrypted.

The file encryption device according to claim 14, wherein the plaintext writing module is further configured to: write a file content of a plaintext length into the encrypted file;

The ciphertext writing module is further configured to: after the plaintext writing module reads the file content of the plaintext length and write the file content into the encrypted file, read the file content of the encrypted length, and the file of the encrypted length The content is encrypted, and the encrypted file content is written into the encrypted file; the first repeating module is further configured to repeatedly start the plaintext writing module and the ciphertext writing module alternately until the The original file is encrypted.

The encryption device for a file according to claim 14, wherein said alternation The encryption unit also includes:

a determining module, configured to determine whether the last file content in the original file should be written into the encrypted file in the form of cipher text;

The plaintext writing module is further configured to directly write the last file content in the original file in the form of a plaintext when the last file content in the original file is not written in the cipher text. Writing the encrypted file;

a supplementary module, configured to determine, when the last file content in the original file is written in the cipher text, whether the length of the last file content in the original file reaches a base value, if the original If the length of the last file content in the file does not reach the base value, the last file content is supplemented so that the length of the last file content reaches the base value;

The ciphertext writing module is further configured to encrypt the encrypted file content and write the encrypted file.

The encryption device for a file according to any one of claims 1 to 3, further comprising:

a determining unit, configured to: read, at the beginning of the original file, the file content of the start length from the beginning of the original file, before writing the encrypted file, determining the start length according to the size of the original file, The encryption length and the length of the plaintext;

And a sending unit, configured to send the start length, the encryption length, the plaintext length, and an encryption rule to a decryption device of the file.

The encryption device for a file according to any one of claims 1 to 3, wherein the alternate encryption unit further comprises:

The first calculating module is configured to calculate the encryption length and the plaintext length according to a predetermined encryption rule in the process of performing encryption according to the ciphertext and the plaintext, to obtain a dynamically changing encryption length and a plaintext length.

The encryption device of the file according to claim 17, wherein the sending unit is further configured to: add a file header at the beginning of the encrypted file, and add the starting length and the The encryption length and the attribute of the plaintext length are written in a file header of the encrypted file; the sending unit is further configured to encapsulate the start length, the encryption length, the plaintext length, and an encryption rule into A decryption device that is sent to the file in the cell.

20. A file decryption apparatus, comprising:

And an initial decryption unit, configured to read the file content of the start length from the beginning of the encrypted file, and write the file content into the decrypted file, wherein the initial length is alternately decrypted from the beginning of the encrypted file to the ciphertext and the plaintext. The length between the starting positions;

The alternate decryption unit is configured to decrypt the file content after the start length of the encrypted file in an alternating form of ciphertext and plaintext, and write the decrypted file content into the decrypted file.

21. The file decryption apparatus according to claim 20, wherein the alternate decryption unit comprises:

The ciphertext reading module is configured to: when the encryption rule adopts a form in which the ciphertext is alternated, the encrypted length of the file content is read, and the encrypted length file content is decrypted, and the decrypted file is decrypted. Content is written into the decrypted file;

a plaintext reading module, configured to: after the ciphertext reading module reads the encrypted length of the file content, read the file content of the plaintext length, and write the file content into the decrypted file;

And a second repeating module, configured to repeatedly start the ciphertext reading module and the plaintext reading module until the current decrypted area of the encrypted file is decrypted.

The file decryption apparatus according to claim 21, wherein the plaintext reading module is further configured to: when the encryption rule adopts a form in which the ciphertext is alternated after the plaintext, the length of the plaintext is read. The content of the file is written into the decrypted file;

The ciphertext reading module is further configured to: after the plaintext reading module reads the file content of the plaintext length, read the file content of the encrypted length, and decrypt the file content of the encrypted length, and decrypt the file content after the decryption The contents of the file are written into the decrypted file;

The second repeating module is further configured to repeatedly start the plaintext reading module and the ciphertext reading module until the current decrypted area of the encrypted file is decrypted.

The file decryption apparatus according to claim 21, further comprising: an obtaining unit, configured to: at the start decryption unit, read the file content of the start length from the beginning of the encrypted file, and write and decrypt the file Before the file, the starting length, the encryption length, the plaintext length, and the encryption rule are obtained.

The apparatus for decrypting a file according to any one of claims 20 to 23, wherein the alternate decryption unit further comprises:

And a second calculating module, configured to calculate the encryption length and the plaintext length according to the encryption rule in the process of decrypting according to the ciphertext and the plaintext, to obtain a dynamically changing encryption length and a plaintext length.

The device for decrypting a file according to any one of claims 20 to 23, further comprising:

a display unit, configured to display content of the decrypted file.

The file decryption apparatus according to claim 25, further comprising: a deleting unit, configured to delete the file content of the decrypted file that does not belong to the current decrypted area.

A system for encrypting and decrypting a file, comprising: the encryption device according to any one of claims 13 to 19, and the decryption device according to any one of claims 20-26.