CN104504342B - Method using invisible character hiding information is encoded based on Unicode - Google Patents

Abstract

The present invention proposes a kind of method using invisible character hiding information based on Unicode codings, mainly includes message embedded mobile GIS and message extraction algorithm.Secret information is hidden by using the Unicode coding characteristics of invisible character, the embedding capacity of secret information is improved on the premise of security is ensured.Using the present invention, secret information can be hidden on the text carrier containing the invisible character such as space using Unicode codings；The insertion form of secret information can neatly be changed according to coding schedule to ensure the safety of information；The embedding capacity of secret information can be effectively improved.

Description

A Method of Hiding Information Using Invisible Characters Based on Unicode Encoding

technical field

The invention relates to a method for hiding information by using invisible characters based on Unicode encoding, and belongs to the technical field of information hiding.

Background technique

With the popularization of computer applications and the rapid development of the Internet, people have put forward higher requirements for network communication security. Different from information encryption technology, information hiding technology guarantees communication security by concealing the existence of the behavior of transmitting messages. At present, with the application of text documents more and more widely, using text documents to hide secret messages has become a research direction in the field of information security. In the field of computer science, Unicode encoding is a universal character set encoding standard, which is widely used in modern operating systems. Almost all word processing software supports Unicode encoding, parsing and storage of text data.

Invisible characters refer to a set of characters that are invisible when the document is printed, including spaces, tabs, and newlines. Generally, using invisible characters to hide secret messages has the advantages of imperceptibility, simple operation, and strong concealment. WbStego4 software is an open source tool that uses invisible characters to hide information. It supports multiple data formats such as TXT, HTML, and PDF. But it does not support information hiding of Chinese text data carrier, and the information embedding capacity is relatively limited, which has great limitations in practical application.

Contents of the invention

The technical problem to be solved by the present invention is to overcome the deficiencies of the existing WbStego4 software technology, to provide a method for hiding information based on Unicode encoding using invisible characters, which is suitable for hiding information in Chinese and English text carriers containing invisible characters based on Unicode encoding Messages can increase the capacity of hidden information under the premise of ensuring security, which can better meet the requirements of covert communication.

The technical solution of the present invention is a method for hiding information based on Unicode encoding using invisible characters, which mainly includes two parts: a message embedding algorithm and an extraction algorithm:

Message embedding algorithm, re-encode the invisible characters in the carrier object according to the code table, and embed the secret message into the carrier object, where the carrier object is Chinese and English text data based on Unicode encoding, and invisible characters include half-width/full-width spaces and Tab characters (the corresponding Unicode codes are 0x20 00, 0x00 30 and 0x09 00). The input data of the embedding algorithm includes carrier object, secret message and code table, and the output data is the carrier with secret.

The message extraction algorithm is the reverse algorithm of the embedded algorithm, and it recovers the secret message from the secret carrier according to the coding table. The input data of the extraction algorithm has a secret carrier and a coding table, and the output data is a secret message.

The method of using invisible characters to hide information based on Unicode encoding of the present invention hides secret messages in text carriers by utilizing the encoding characteristics of invisible characters. The method comprises the following steps:

(1) The sender and the receiver agree on a secret key, and construct a coding table according to the secret key;

(2) The sender selects the carrier object, and according to the encoding table generated in step (1), embeds the secret message into the carrier object through information embedding to obtain the secret carrier;

(3) The sender transmits the encrypted carrier obtained in the step (2) to the receiver through the communication channel;

(4) According to the encoding table generated in step (1), the receiver extracts the secret message from the secret carrier received in step (3) through an extraction algorithm to obtain the secret message.

The beneficial effect of the present invention compared with prior art is:

(1) In the present invention, the selection of carrier objects is wider. The carrier object suitable for hiding secret messages can choose text data based on Unicode encoding to meet the needs of practical applications.

(2) In the present invention, the security of the algorithm is guaranteed by using the secret key generated by the secret key generator. The secret key can control the generation of the encoding table. On the premise of ensuring the security of the information hiding algorithm, the message embedding/extraction operation and the message encryption/decryption operation are combined to reduce the complexity and energy consumption of the operation in practical applications.

(3) In the present invention, the capacity of embedded information is increased by using the encoding table. When compiling the code table, a code table composed of 256 one-to-one mapping relations is designed by using the redundant invisible character code words in the Unicode code, and the mapping relationship of the code table is controlled by the secret key. The encoding table increases the information rate per embedding from 1 bit to 8 bits per embedding.

Description of drawings

Fig. 1 is the realization flowchart of the method embodiment of the present invention;

Fig. 2 is the implementation flowchart of message embedding algorithm in the inventive method;

Fig. 3 is an implementation flow chart of the message extraction algorithm in the method of the present invention.

Detailed ways

In order to make the above objects, features and advantages of the present invention more obvious and understandable, the present invention will be further described below through specific embodiments and accompanying drawings.

As shown in Figure 1 , it is a schematic diagram of the implementation flow of the present invention, and the information hiding method can be expressed as a six-tuple, that is, ∑=<C, S, T _k , C', E _k , D _k >, where C is The set of carrier objects, S is the set of secret messages, T _k is the coding table constructed according to the secret key k, C′ is the set of secret carriers obtained after the secret message is hidden by the carrier object, E _k is the message embedding algorithm, and D _k is the message embedding algorithm. extraction algorithm. In the information hiding method Σ, there are two main algorithm modules: a message embedding algorithm module and a message extraction algorithm module, which are called by the sender and receiver respectively. The function description of each module is as follows:

1. Message embedding algorithm

The sender constructs the encoding table T _k according to the secret key k, embeds the secret information S input by the sender into the selected carrier object C, and outputs the encrypted carrier C′. Then, the sender transmits the encrypted carrier C' to the receiver through the communication channel. The process of executing the message embedding algorithm _Ek can be expressed as:

E _k : C×M×T _k →C′

2. Message extraction algorithm

The receiver constructs the encoding table T _k according to the extraction key k, and extracts the secret information M from the secret carrier C′ obtained from the sender through the extraction algorithm. The process of executing the message extraction algorithm _Dk can be expressed as:

D _k :C′×T _k →M

As shown in Figure 1, the specific implementation process of the present invention is as follows:

1. Code table structure

The present invention controls the generation of the encoding table T _k through the secret key k shared by the sender and the receiver, and increases the capacity of hidden information under the premise of ensuring encoding security to meet the requirements of practical applications. The specific implementation steps of constructing the encoding table are as follows:

(1) The key k must be a 2048-bit binary string, which can be expressed as

k=(n ₀ ,n ₁ ,...,n _i ,...,n ₂₅₅ ),n _i ∈N∩[0,255], i=0,1,...255

In addition, each component n _i of the key k must also satisfy the following conditions

The above description shows that the key k can be expressed as a permutation of an integer sequence from 0 to 255, as shown in the following formula

k=perms(0,1,2,...,255)

Where perms() is the permutation function.

(2) According to the characteristics of the Unicode code, the sender and the receiver find the optional codewords of 256 invisible characters in advance, as the basis for the construction of the code table shared by both parties (each codeword must be a 2-byte Unicode coding). As shown in Table 1, a hexadecimal representation example of 256 optional codewords is given.

(3) According to step (1) and step (2), establish a coding table T _k from the key to the optional codeword. Table 1 shows the encoding table constructed when the key k=(0, 1, 2, . . . , 255).

Table 1. Encoding table

m numbers m numbers m numbers m numbers m numbers m numbers m numbers 00 00 D8 25 01 E4 4A 02 F8 6F 04 E3 94 05 F7 B9 07 E2 DE 08 F6 01 00 D9 26 01 E5 4B 03 D8 70 04 E4 95 05 F8 BA 07 E3 DF 08 F7 02 00DA 27 01 E6 4C 03 D9 71 04 E5 96 06 D8 BB 07 E4 E0 08 F8 03 00 DB 28 01 E7 4D 03 DA 72 04 E6 97 06 D9 BC 07 E5 E1 09 D8 04 00 DC 29 01 F0 4E 03 DB 73 04 E7 98 06DA BD 07 E6 E2 09 D9 05 00 DD 2A 01 F1 4F 03 DC 74 04 F0 99 06DB BE 07 E7 E3 09DA 06 00 DE 2B 01 F2 50 03 DD 75 04 F1 9A 06 DC BF 07 F0 E4 09 DB 07 00 DF 2C 01 F3 51 03 DE 76 04 F2 9B 06 DD C0 07 F1 E5 09 DC 08 00 E0 2D 01 F4 52 03 DF 77 04 F3 9C 06 DE C1 07 F2 E6 09 DD 09 00 E1 2E 01 F5 53 03 E0 78 04 F4 9D 06 DF C2 07 F3 E7 09 DE 0A 00 E2 2F 01 F6 54 03 E1 79 04 F5 9E 06 E0 C3 07 F4 E8 09 DF 0B 00 E3 30 01 F7 55 03 E2 7A 04 F6 9F 06 E1 C4 07 F5 E9 09 E0 0C 00 E4 31 01 F8 56 03 E3 7B 04 F7 A0 06 E2 C5 07 F6 EA 09 E1 0D 00 E5 32 02 D8 57 03 E4 7C 04 F8 A1 06 E3 C6 07 F7 EB 09 E2 0E 00 E6 33 02 D9 58 03 E5 7D 05 D8 A2 06 E4 C7 07 F8 EC 09 E3 0F 00 E7 34 02 DA 59 03 E6 7E 05 D9 A3 06 E5 C8 08 D8 ED 09 E4 10 00 F0 35 02 DB 5A 03 E7 7F 05DA A4 06 E6 C9 08 D9 EE 09 E5 11 00 F1 36 02 DC 5B 03 F0 80 05DB A5 06 E7 CA 08 DA EF 09 E6 12 00 F2 37 02 DD 5C 03 F1 81 05 DC A6 06 F0 CB 08DB F0 09 E7 13 00 F3 38 02 DE 5D 03 F2 82 05 DD A7 06 F1 CC 08 DC F1 09 F0 14 00 F4 39 02 DF 5E 03 F3 83 05 DE A8 06 F2 cd 08 DD F2 09 F1 15 00 F5 3A 02 E0 5F 03 F4 84 05 DF A9 06 F3 CE 08 DE F3 09 F2 16 00 F6 3B 02 E1 60 03 F5 85 05 E0 AAA 06 F4 CF 08 DF F4 09 F3 17 00 F7 3C 02 E2 61 03 F6 86 05 E1 AB 06 F5 D0 08 E0 F5 09 F4 18 00 F8 3D 02 E3 62 03 F7 87 05 E2 AC 06 F6 D1 08 E1 F6 09 F5 19 01 D8 3E 02 E4 63 03 F8 88 05 E3 AD 06 F7 D2 08 E2 F7 09 F6 1A 01 D9 3F 02 E5 64 04 D8 89 05 E4 AE 06 F8 D3 08 E3 F8 09 F7 1B 01DA 40 02 E6 65 04 D9 8A 05 E5 AF 07 D8 D4 08 E4 F9 09 F8 1C 01 DB 41 02 E7 66 04DA 8B 05 E6 B0 07 D9 D5 08 E5 FA 0A D8 1D 01 DC 42 02 F0 67 04 DB 8C 05 E7 B1 07DA D6 08 E6 Facebook 0A D9 1E 01 DD 43 02 F1 68 04 DC 8D 05 F0 B2 07DB D7 08 E7 FC 0A DA 1F 01 DE 44 02 F2 69 04 DD 8E 05 F1 B3 07 DC D8 08 F0 FD 0A DB 20 01 DF 45 02 F3 6A 04 DE 8F 05 F2 B4 07 DD D9 08 F1 FE 0A DC twenty one 01 E0 46 02 F4 6B 04 DF 90 05 F3 B5 07 DE DA 08 F2 FF 0A DD twenty two 01 E1 47 02 F5 6C 04 E0 91 05 F4 B6 07 DF DB 08 F3 twenty three 01 E2 48 02 F6 6D 04 E1 92 05 F5 B7 07 E0 DC 08 F4 twenty four 01 E3 49 02 F7 6E 04 E2 93 05 F6 B8 07 E1 DD 08 F5

In the present invention, the encoding table is used as the input of the message embedding algorithm module and the extraction algorithm module, and the encoding table constructed by the sender and the receiver through the secret key k is the same, so the encoding table T _k input to the embedding algorithm module is the same as The coding table T _k input to the extraction algorithm module is consistent.

2. Message embedding

In the present invention, the message embedding algorithm module executes the embedding algorithm E() can be expressed as

c'=E(c,m,T _k )

Among them, the input parameters of the module include the carrier object c, the secret message m to be embedded and the encoding table T _k generated by embedding the secret key k, and the output of the module is the secret carrier c′ containing the secret message. In addition, the present invention requires that the carrier c of the embedded information is text data based on Unicode encoding, including text data in TXT format text and Word, PDF, XML, and HTML compound documents; and m is processed as a byte stream in the embedding module , so m can be TXT text data and JPEG image data.

The implementation flow chart of the embedded algorithm is shown in Figure 2, and the specific implementation steps are as follows:

(1) Carry out preprocessing to the input carrier object c, replace the code word that appears in coding table T _k in c with 0x2000;

(2) Read the 2-byte data xx of c sequentially, and judge whether the value of xx is 0x0000;

(3) If the result in step (2) is no, then perform step (4), otherwise perform step (12a);

(4) Determine whether xx is an invisible character, including half-width/full-width spaces and tabs, and their corresponding Unicode codes are 0x2000, 0x0030 and 0x0900;

(5) If the result in step (4) is no, then jump to step (2), otherwise execute step (6);

(6) For the input secret message s, read 1 byte of data y;

(7) Determine whether the y value is EOF;

(8) If the result in step (7) is no, then perform step (9), otherwise perform step (12b);

(9) To the input coding table T _k , search for the code word zz corresponding to the y value in T _k ;

(10) use the zz value in the step (9) to replace the xx value in the obtained c of the step (5);

(11) Repeat step (2);

(12a) Outputting a prompt message that the embedding capacity of the carrier is insufficient.

(12b) Output the changed c, which is the secret carrier c'.

3. Message extraction

In the present invention, the message extraction algorithm module executes the extraction algorithm D(), which can be expressed as

m=D(c',T _k' )

Among them, the input parameters of the module include the secret carrier c' containing the secret message and the code table T _k ' generated by extracting the secret key k', and the output of the module is the extracted secret message m. In particular, in order to maintain the consistency of the encoding tables T _k and T _k' , the embedding key k and the extraction key k' are the same in the present invention.

The implementation flowchart of the extraction algorithm is shown in Figure 3, and the specific implementation steps are as follows:

(1) Read 2 bytes of data yy for the input tape carrier c';

(2) Determine whether the value of yy is EOF;

(3) If the result in step (2) is no, then execute step (4), otherwise execute step (8);

(4) according to input coding table T _{k '} , judge whether the yy value in the step (2) is the code word in T _{k '} ;

(5) If the result in step (4) is no, then jump to step (1), otherwise execute step (6);

(6) Search T _k' to obtain the m value corresponding to the yy value;

(7) Repeat step (1);

(8) Output the secret message m.

The above embodiments are only used to illustrate the technical solution of the present invention and not to limit it. Those of ordinary skill in the art can modify or equivalently replace the technical solution of the present invention without departing from the spirit and scope of the present invention. The scope of protection should be determined by the claims.

Claims (6)

1. A method of utilizing invisible characters to hide information based on Unicode encoding, which is suitable for hiding messages based on the text carrier containing invisible characters based on Unicode encoding, comprising the following steps: (1) The sender and the receiver agree on the secret key, and control the generation of the encoding table through the secret key, and use the invisible characters in the Unicode code to construct the encoding table according to the secret key; control the code table through the secret key k shared by the sender and the receiver The generation of coding table T _k , the step of constructing coding table is: (1-1) The secret key k must be a 2048-bit binary string expressed in decimal as: n ₀ n ₁ …n _i …n ₂₅₅ , n _i ∈ N∩[0,255], i=0,1,…255, In addition, the components n _i and n _j of the secret key k satisfy the following conditions: <mrow><mo>&amp;ForAll;</mo><mi>i</mi><mo>,</mo><mi>j</mi><mo>&amp;Element;</mo><mo>{</mo><mn>0</mn><mo>,</mo><mn>1</mn><mo>,</mo><mo>...</mo><mo>,</mo><mn>255</mn><mo>}</mo><mo>,</mo><mi>i</mi><mo>&amp;NotEqual;</mo><mi>j</mi><mo>&amp;DoubleRightArrow;</mo><msub><mi>n</mi><mi>i</mi></msub><mo>&amp;NotEqual;</mo><msub><mi>n</mi><mi>j</mi></msub><mo>,</mo></mrow> The secret key k is expressed as a permutation of an integer sequence from 0 to 255, as shown in the following formula: k=perms(0,1,2,...,255), where perms() is a replacement function; (1-2) According to the characteristics of the Unicode code, the sender and the receiver search out the optional codewords of 256 invisible characters in advance, as the basis for the construction of the code table shared by both parties; (1-3) according to step (1-1) and step (1-2), set up the coding table T _k from secret key to optional code word; (2) The sender selects text data based on Unicode encoding as the carrier object, re-encodes the invisible characters in the carrier object according to the encoding table generated in step (1), embeds the secret message into the carrier object, and obtains the secret message carrier; (3) The sender transmits the encrypted carrier obtained in the step (2) to the receiver through the communication channel; (4) The receiver extracts the secret message from the secret carrier received in step (3) according to the encoding table generated in step (1), and obtains the secret message. 2. The method according to claim 1, characterized in that: step (2) embeds the secret message in the carrier object by executing the embedding algorithm E (), and the embedding algorithm E () is expressed as c'=E(c,m,T _k ), Among them, the input parameters are the carrier object c, the secret message m to be embedded and the encoding table T _k generated by embedding the key k, and the output is the secret carrier c′ containing the secret message. 3. The method according to claim 2, characterized in that: the carrier object c is text data based on Unicode encoding, including text data in TXT format text and Word, PDF, XML, and HTML compound documents; secret message m is used as a character Throttling mode for processing, m is TXT text data or JPEG image data. 4. the method for claim 2 is characterized in that, the concrete realization step of described embedding algorithm is: (2-1) Carry out preprocessing to the input carrier object c, replace the code word that appears in coding table T _k in c with 0x2000; (2-2) Sequentially read the 2-byte data xx of c, and judge whether the value of xx is 0x00 00; (2-3) If the result in step (2-2) is no, then execute step (2-4), otherwise execute step (2-12a); (2-4) Determine whether xx is an invisible character, including half-width/full-width spaces and tabs, and their corresponding Unicode codes are 0x20 00, 0x00 30 and 0x09 00; (2-5) If the result in step (2-4) is no, then jump to step (2-2), otherwise execute step (2-6); (2-6) For the input secret message s, read 1 byte of data y; (2-7) Determine whether the y value is EOF; (2-8) If the result in step (2-7) is no, then perform step (2-9), otherwise perform step (2-12b); (2-9) To the input coding table T _k , search for the code word zz corresponding to the y value in T _k ; (2-10) use the zz value in step (2-9) to replace the xx value in c obtained in step (2-5); (2-11) Repeat step (2-2); (2-12a) outputting a message indicating that the embedding capacity of the carrier is insufficient; (2-12b) Output the changed c, which is the secret carrier c'. 5. The method according to claim 4, characterized in that: step (4) extracts the secret message from the tape secret carrier by executing the extraction algorithm D (), and the extraction algorithm D () is expressed as m=D(c', T _k' ), Among them, the input parameter is the code table T _k ' generated by the secret carrier c' containing the secret message and the extracted secret key k', and the output is the extracted secret message m; in order to maintain the consistency of the code table T _k and T _k' , the embedding key k is the same as the extraction key k′. 6. the method for claim 5 is characterized in that, the concrete realization step of described extracting algorithm is: (4-1) read 2 bytes of data yy to the input tape carrier c'; (4-2) Determine whether the value of yy is EOF; (4-3) If the result in step (4-2) is no, then execute step (4-4), otherwise execute step (4-8); (4-4) according to input coding table T _{k '} , judge whether the yy value in the step (4-2) is the code word in T _{k '} ; (4-5) If the result in step (4-4) is no, then jump to step (4-1), otherwise execute step (4-6); (4-6) Find T _k' to obtain the m value corresponding to the yy value; (4-7) Repeat step (4-1); (4-8) Output the secret message m.