CN103942284B - File fingerprint information extracting method based on sine function - Google Patents
File fingerprint information extracting method based on sine function Download PDFInfo
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- CN103942284B CN103942284B CN201410138961.9A CN201410138961A CN103942284B CN 103942284 B CN103942284 B CN 103942284B CN 201410138961 A CN201410138961 A CN 201410138961A CN 103942284 B CN103942284 B CN 103942284B
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F21/00—Security arrangements for protecting computers, components thereof, programs or data against unauthorised activity
- G06F21/60—Protecting data
- G06F21/64—Protecting data integrity, e.g. using checksums, certificates or signatures
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F2221/00—Indexing scheme relating to security arrangements for protecting computers, components thereof, programs or data against unauthorised activity
- G06F2221/21—Indexing scheme relating to G06F21/00 and subgroups addressing additional information or applications relating to security arrangements for protecting computers, components thereof, programs or data against unauthorised activity
- G06F2221/2107—File encryption
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Abstract
The invention relates to a file fingerprint information extracting method based on a sine function. The extracting method includes the steps that a position sequence is generated by using the sine function and serves as the position value when file fingerprint information is extracted from the file content, after the value is extracted out, a permutation matrix is used for permutation to obtain a final file fingerprint, and confidentiality of file plain texts is achieved to a certain degree. A default value of the permutation matrix can be set or appointed by a user himself, the strategy is easy to implement and high in scalability, the fingerprint with any bit length can be provided, the fingerprint information can be dispersed in the file content in any form, and the file fingerprint information extracting method is very suitable for the scene where data are encrypted or decrypted through stream ciphers.
Description
Technical field
The invention belongs to computer application field, is related to a kind of acquisition methods of file encryption information.
Background technology
In computer utility, particularly information security field, file fingerprint information is an important method and plan
Slightly.Called file fingerprint, referring to can uniquely indicate the feature of certain file, and each different file can have different fingers
Stricture of vagina information.File fingerprint plays the role of very important in all many-sides such as protection data integrity, identifications.In many fields
Under scape, need using simpler effective file fingerprint information extraction mechanism.
Existing file fingerprint information extracting method, mainly concentrates on the related hash function of searching to enter file content
Row is processed.Such as in terms of checking data integrity, data publisher carries out hash to file content first, and Hash Value is adhered to
In the head or afterbody of file, after Data receiver's receiving data, then hash is carried out to file content, by Hash Value with it is original
Hash Value is compared, so as to judge whether data are tampered or damage.In the industry cycle, comparative maturity and widely used hash letter
Number has MDx, SHA-x etc..
However, in stream cipher mechanism, to carry out encryption and decryption, conventional utilization using different keys to each file
File fingerprint is unaccommodated come the method for identifying different files, since it is desired that in top of file or the additional fingerprint letter of afterbody
Breath, have impact on file size, and finger print information is disclosed, once destroyed, file just has the risk that cannot be decrypted.Cause
This, studies a kind of file fingerprint information extracting method that can be used in stream cipher system and is very important.
The content of the invention
The present invention technology solve problem be：Overcome the deficiencies in the prior art, there is provided a kind of text based on SIN function
Part finger print information extracting method, is particularly suitable for carrying out encryption and decryption to data in stream cipher system.
The present invention technical solution be：A kind of file fingerprint information extracting method based on SIN function, including such as
Lower step：
（1）Using random sequence generator, random sequences of the length for n bit are generated；Described random sequences are only
Generate once, be not repeated to generate.
（2）File size A for obtaining file content and calculating by bit, is calculated positional information, from text using following formula
Corresponding bit is extracted in part content as initial fingerprint information,
In formula, S is that 1 to the integer between n, F (S) is the S position extracted from file content, and L is big by file
The diffusion coefficient that little A is determined, when A is less than 16KB, L=217Bit, when A is more than or equal to 16KB, L=A；
（3）The information that corresponding bit is extracted from file content generates the initial fingerprint information of n bit；Work as step（2）Fall into a trap
When the extraction position number for obtaining is equal to n, the bit information extracted from n correspondence position is initial fingerprint information, works as step
（2）In calculated extraction position number be less than n when, using from correspondence position extract utilization bit information, to step（1）
The sequence immediately of middle generation proceeds by order and replaces from highest order, thus obtains the initial fingerprint information of n bit；
（4）The initial fingerprint information of n bit is entered into line replacement using permutation matrix, so as to obtain final file fingerprint letter
Breath.Described permutation matrix is the two-dimensional array of a 16*16, and each element in array is different from, but each is first
The value of element belongs to a value in 0～255.Permutation matrix is fixed default matrix or is randomly selected by user.
Present invention advantage compared with prior art is：
（1）Realize simple.A position sequence is produced using SIN function, the sequence is extracted as from file content
Positional value during file fingerprint information, line replacement is entered after taking-up value with a permutation matrix, so as to obtain final file fingerprint,
Traditional HASH methods are compared, the inventive method to source file to be encrypted without the need for carrying out any change（Traditional HASH methods
Need that the hash values of file are attached in the middle of file）, it is easy to accomplish；
（2）In being especially suitable for user's stream cipher system.In the case where file content is not changed, realize identifying each file
Identity function, be that different files produce different key streams.Traditional method must be changed to source file content, if
Once file goes wrong in transmitting procedure, then source file cannot be decrypted, and using the inventive method the problems referred to above can be avoided；
（3）Safety is higher.Using random array is supplied, it is allowed to be adapted to different size of file, and peace well is provided
Quan Xing.Traditional method is weak for the safety of small documents, because small documents, can carry out brute-force using traditional method and break
Solution, and using file fingerprint and supply random data, it is ensured that even if in the case of file content very little, also providing more
The guarantee of safety.
Description of the drawings
Fig. 1 is the FB(flow block) of the inventive method.
Specific embodiment
As shown in figure 1, the flow chart for the present invention based on the file fingerprint information extracting method of SIN function, mainly includes
Following several steps：
First, initial fingerprint is generated
According to file content and file size（By bit length computation）, with reference to SIN function and fingerprint positions computing formula,
The initial fingerprint information of corresponding digit is extracted from file content.
（1）Obtain file size；
（2）Finger print information is calculated according to following fingerprint computing formula according to file size corresponding in file content
Position；
Formula explanation：The length of file fingerprint information is n bits, and S is the integer between [1, n], and expression will take the fingerprint
S positions；L is diffusion coefficient, is determined by the size of file, and when file size is less than 16KB, L takes 217, other situations L are literary
The size of part（Calculate by bit）；F (S) represents the particular location for extracting file corresponding to S positions.
The derivation of above-mentioned formula is as follows：
Because relation function adopts SIN function, bit subscript hereof to start to calculate from 0, therefore
Therefore equation below is drawn：
Above-mentioned formula is why using realizing the generation to file fingerprint position, its reason is based on SIN function：1）
Because SIN function produce positional information it is more more disguised than the positional information that linear function is produced, and than higher order functionality with
Index/logarithmic function is simple；2）The coefficient and file content of function is associated, it is ensured that different files has different position letters
Breath, even if identical file size, its finger print information value is also different；3）In order to solve the problems, such as small documents, benefit is taken
The form of the random array of foot carries out Safety assurance measures.
（3）According to the position obtained（With the position that bit is counted）Corresponding initial fingerprint information is read from file content
Position, if file size is too little, as needed from the Bit String filling initial fingerprint information for supplying taking-up corresponding length in array.
2nd, array generation is supplied
By random sequence generator（One random sequences generating function）Generate a bit array, the array be one with
File fingerprint message length identical Bit String, and once generate, forever use.
（1）Isometric with a finger print information length random sequences are calculated using random sequence generator；
（2）Whether the randomness of the random sequences generated using pre-set randomness detected rule detection is conformed to
Ask, if do not meet regenerating random sequences；The random sequences of the generation are and supply array if meeting the requirements；
3rd, finger print information displacement
An acquiescence permutation matrix can be arranged by developer, and interface is provided and choose whether to specify displacement square for user
Battle array, is entered after line replacement to initial fingerprint information with permutation matrix and draws final file fingerprint information.
（1）It is determined that the permutation matrix still specified using user using acquiescence permutation matrix；
（2）Initial fingerprint information is entered into line replacement using permutation matrix, final file fingerprint information is obtained.
Permutation matrix is the two-dimensional array of a 16*16, and each element is different in array, and belongs to 0～255
In a value, that is to say, that permutation matrix is exactly one of 0～255 arrangement.So-called acquiescence permutation matrix, i.e., by algorithm certainly
Dynamic random generation；And the permutation matrix that user specifies, i.e. user oneself can also generate an arrangement, with the shape of algorithm parameter
Formula is input into.
Permutation matrix is used for entering line translation to original document finger print information so as to more complicated with the relation of file data,
The confidentiality of file fingerprint acquisition of information is improved, the effect of permutation matrix is the position for upsetting bit in file fingerprint information,
Therefore element can not repeat in two-dimensional array.
The content not being described in detail in description of the invention belongs to the known technology of those skilled in the art.
Claims (3)
1. a kind of file fingerprint information extracting method based on SIN function, it is characterised in that comprise the steps：
(1) random sequence generator is utilized, random sequences of the length for n bit are generated；
(2) file size A for obtaining file content and calculating by bit, using following formula positional information is calculated,
In formula, S is that 1 to the integer between n, F (S) is the S position extracted from file content, and L is to be determined by file size A
Fixed diffusion coefficient, when A is less than 16KB, L=217Bit, when A is more than or equal to 16KB, L=A；
(3) information that corresponding bit is extracted from file content generates the initial fingerprint information of n bit；When calculating in step (2)
When the extraction position number for arriving is equal to n, the bit information extracted from n correspondence position is initial fingerprint information, when step (2)
In calculated extraction position number when being less than n, using the bit information extracted from correspondence position, to what is generated in step (1)
Immediately sequence proceeds by order and replaces from highest order, thus obtains the initial fingerprint information of n bit；
(4) the initial fingerprint information of n bit is entered into line replacement using permutation matrix, so as to obtain final file fingerprint information；
Described permutation matrix is the two-dimensional array of a 16*16, and each element in array is different from, but each element
Value belongs to a value in 0～255.
2. a kind of file fingerprint information extracting method based on SIN function according to claim 1, it is characterised in that：Institute
The random sequences stated are only generated once, are not repeated to generate.
3. a kind of file fingerprint information extracting method based on SIN function according to claim 1, it is characterised in that：Institute
The permutation matrix stated is fixed default matrix or is randomly selected by user.
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| CN101281581A (en) * | 2007-09-27 | 2008-10-08 | 北京数字证书认证中心有限公司 | Method for checking whether contents of paper file is distorted or not |
| CN102880833A (en) * | 2012-08-28 | 2013-01-16 | 福州讯华信息技术有限公司 | Two-dimensional code anti-fake verification method for documents |
| CN102930317A (en) * | 2012-11-30 | 2013-02-13 | 中企永联数据交换技术（北京）有限公司 | Device for generating two-dimension code identifiers of books, two-dimension code identification device and system |
| CN103544408A (en) * | 2013-09-23 | 2014-01-29 | 中山大学 | Method for embedment and extraction of PDF document hidden information according to composite font |
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| JP4424422B2 (en) * | 2008-01-18 | 2010-03-03 | 富士ゼロックス株式会社 | Information processing apparatus, information processing system, and program |
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Patent Citations (4)
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| CN101281581A (en) * | 2007-09-27 | 2008-10-08 | 北京数字证书认证中心有限公司 | Method for checking whether contents of paper file is distorted or not |
| CN102880833A (en) * | 2012-08-28 | 2013-01-16 | 福州讯华信息技术有限公司 | Two-dimensional code anti-fake verification method for documents |
| CN102930317A (en) * | 2012-11-30 | 2013-02-13 | 中企永联数据交换技术（北京）有限公司 | Device for generating two-dimension code identifiers of books, two-dimension code identification device and system |
| CN103544408A (en) * | 2013-09-23 | 2014-01-29 | 中山大学 | Method for embedment and extraction of PDF document hidden information according to composite font |
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| 计算机安全系统中随机序列发生器的研究;苏桂平 等;《计算机研究与发展》;20030731;第40卷(第7期);994-1000 * |
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