KR100876525B1 - Complementary method of symmetric key cryptography for multilingual text string encryption - Google Patents

Abstract

According to the present invention, when a multilingual text string such as Korean or Japanese, which is handled by a computer terminal, is encrypted with a symmetric key encryption algorithm, the cipher text cannot be displayed on the terminal beyond the character code area, and the same length as that of the original text is prevented. The present invention relates to a method for generating a cipher text. In particular, in encrypting a string treated as a computer terminal by a multi-step procedure based on a mathematical operation, some bits of the multilingual character code are fixed and only the remaining bits are encrypted. And a process of allowing the character code region of the ciphertext to be limited within the region of the fixed bit.

Description

Complement method for many languages text characters encryption algorithm}

1 is a view showing that when multilingual codes such as Korean and Japanese are encrypted with an arbitrary secret key according to an embodiment of the present invention, the result may be out of the corresponding code area.

2 is a diagram illustrating a method of dividing an original text into a plurality of bit masking groups so that the code region of the cipher text does not leave the code region of the original text, and correcting a secret key with a bit mask corresponding to each group according to an embodiment of the present invention. One drawing.

3 is a view showing an embodiment in which some bits are fixed and only the remaining bits are encrypted according to an embodiment of the present invention.

4 is a flowchart for performing an encryption procedure by receiving an original text and a secret key according to an embodiment of the present invention.

FIG. 5 is a flowchart of a sub procedure of FIG. 4 according to an embodiment of the present invention, in which an encryption procedure is performed when a corresponding character is an ASCII code while reading a string of original text one byte. FIG.

FIG. 6 is a sub-procedure of FIG. 4 according to an embodiment of the present invention. When a character string is a multi-language code while reading the character string of the original text one by one, the flowchart further performs an encryption procedure after additionally reading one byte. .

<Description of the code for the main part>

104: symmetric key encryption algorithm (in the embodiment of the present invention simply performs an XOR operation)

221: Bit masked secret key in specific area 1

320: secret key area

330: bit mask

340: Beek masked secret key area

403: Determine whether ASCII code by reading the original text string by 1 byte

404: ASCII encryption function call in case of ASCII code

407: If it is not ASCII code, read additional 1 byte, then call multilingual encryption function

550: In the ASCII encryption function, when the character code read from the original text corresponds to an arbitrary region 1, a procedure of correcting the secret key with a bit mask of the region

560: In the ASCII encryption function, if the character code read from the original text corresponds to an arbitrary area 2, a procedure for correcting the secret key with a bit mask of the corresponding area

6050: In the multi-language encryption function, when the upper one byte character code read from the original text corresponds to an arbitrary region 1, a procedure for correcting the secret key for encrypting the upper one byte with the bit mask of the region.

6060: In the multi-language encryption function, if the high-order byte character code read from the original text belongs to an arbitrary area 2, a procedure for correcting the secret key for encrypting the high-order byte with the bit mask of the corresponding area.

6090: In the multilingual encryption function, when the upper one byte character code read from the original text belongs to an arbitrary region 1, a procedure for correcting the secret key for encrypting the lower one byte with a bit mask of the region.

6100: In the multi-language encryption function, when the upper 1 byte character code read from the original text belongs to an arbitrary area 2, a procedure for correcting the secret key for encrypting the lower 1 byte with the bit mask of the corresponding area.

According to the present invention, when a multilingual text string such as Korean or Japanese, which is handled by a computer terminal, is encrypted with a symmetric key encryption algorithm, the cipher text cannot be displayed on the terminal beyond the character code area, and the same length as that of the original text is prevented. The present invention relates to a method for generating a cipher text, and more particularly, to encrypting a string treated as a computer terminal by a multi-step procedure based on a mathematical operation, in which some bits of the multilingual character code are fixed and only the remaining bits are encrypted. By performing the above, the character code area of the cipher text is restricted in the area of the fixed bit.

In general, there are two types of encryption algorithms used in computer terminals. One is a symmetric algorithm that is mainly used for encrypting data such as files and packets, and the other is an asymmetric algorithm that is mainly used in authentication systems such as financial certificates. to be.

The difference between symmetric and asymmetric algorithms is whether the same key is used for encryption and decryption. The symmetric algorithm uses the same key for encryption and decryption, whereas the asymmetric algorithm has a pair of keys used for encryption and decryption, and any key among the paired keys. When encrypted, decryption is possible only with the other key.

The present invention relates to a method for correcting an encryption result for a multilingual text string such as Korean and Japanese with a character code that can be displayed on a terminal. The following are the related arts of a symmetric algorithm that is a technical field of the present invention.

The symmetric algorithm is representative of the Data Encryption Standard (DES) algorithm developed by IBM. DES is a block cipher algorithm developed by IBM that was adopted by the National Bureau of Standards (NBS) in 1977. A block cipher algorithm that encrypts 64-bit input blocks using 56-bit secret keys.Its scope of use extends from the US Federal Department of Data Protection to ANSI's standard cryptographic algorithms. Most widely used in the world. However, the general view is that it is no longer secure because of the short key length of 56 bits. To compensate for this, it is recommended to use 3DES (Triple DES), which repeats DES three times, and recently, AES, the next generation US standard, has been determined and used.

As an alternative to solve the stability problem caused by the short key length of 56 bits of DES, Triple DES is used, which uses DES three times with three keys. Despite the disadvantage that 3DES is about 3 times slower than DES, 3DES is easily implemented using DES and has been used in various standards due to its advantages of solving the safety problem of DES.

In response to the need for block ciphers to replace the DES, which expired in 1998, NIST pushed ahead with the development of the Advanced Encryption Standard (AES) as a strong encryption algorithm standard for future government and commercial use. NIST announced a final AES algorithm selected on October 2, 2000, after publicly evaluating 15 candidate algorithms over three years. . The block cipher adopted by AES was developed by Daemem and Rijmen and named RIJNDAEL, and became a new industry standard in December 2001, replacing DES and Triple DES.

We developed an algorithm to be used as a standard in Korea. SEED is a symmetric key 128-bit block encryption algorithm developed by KISA and ETRI in 1999 to protect information and private privacy in the private sector. It was adopted as the standard of the Korea Information and Communication Technology Association (TTA) in September, and it was confirmed as the international standard at the 31st ISO / IEC International Standardization Meeting in November 2005.

However, the conventional technique is a general technique for encrypting data. When encrypting a multilingual text string such as Korean or Japanese, the result may be out of the original code region, and thus, when stored as a binary code, there is a problem. However, when outputting as text, a problem occurs in that a character code or control code of an area that cannot be output to a terminal is inserted.

Complementing this point, many methods of encrypting multi-language codes such as Korean and Japanese are cut into 1-byte hexa code, respectively, but in this case, the length is doubled. Using the compression algorithm in parallel can reduce the length, but the problem is that the compressed length is not constant. In addition, a method of encrypting multi-language codes such as Korean and Japanese as separate code tables for encryption, or using a substitution method is introduced, but this also has disadvantages that increase the length of the original text or is based on bit operations. Substitutions such as unsubstitution are not preferable as the algorithm against the times.

Therefore, when multi-language text strings such as Korean and Japanese are encrypted, a technique is required in which the result retains the code region of the original text and the length is the same as the original.

When encrypting multilingual text strings such as Korean and Japanese with the existing symmetric encryption algorithm, the following two problems occur. First, a passphrase may not be displayed on the terminal because it is outside the character code field. Second, there are many modified algorithms to prevent the first problem, but the disadvantage is that the length of the cipher text is longer than the original text. In an ideal algorithm that complements the above two problems, the length of the ciphertext should be the same as the length of the original text without the region of the ciphertext leaving the character code region.

 The present invention has been started for the purpose of implementing the above-described ideal algorithm, the present invention is not a symmetric encryption algorithm of the new concept itself, it can be said to be an intermediate procedure to complement the existing symmetric encryption algorithm.

SUMMARY OF THE INVENTION An object of the present invention is to correct an encryption result for a multi-language text string such as Korean or Japanese handled by a computer terminal with a character code that can be displayed on a terminal, and to manage the encrypted result in a text form instead of binary, by using an email or the Internet. Even in bulletin boards, messengers, word processors, etc., it can be stored in an encrypted form and can be printed as a paper document if necessary.

In addition, an object of the present invention is that the encrypted result is the same as the original length, so that the encrypted data can be handled as it is, without modifying and developing a computer system for transmitting and storing data.

For example, in data transmission, a communication packet between systems makes and receives a packet in a predefined form between a transmitting side and a receiving side, which may have a fixed length or a variable length. In the case of fixed length, if there is a Korean field of length 20 at a specific location in the packet, and you need to encrypt this field, you can use the existing encryption algorithm to increase the length, so the system can be handled to handle the increased length. Modifications should be developed. However, using the technique of the present invention, since the result of encryption is the same length, there is no cost problem of modifying and developing the system.

In data storage, the fields constituting a table of a database may have a fixed length and may have a variable length. In the case of a fixed length dealing with Hangul, if the length of the encrypted result is changed, there is a cost problem of modifying and developing the system to store the changed length, but using the technique of the present invention can reduce such a cost. .

The method of the present invention for achieving the above object; When multilingual text strings such as Korean and Japanese, which are handled by a computer terminal, are encrypted with a symmetric key cryptographic algorithm, the cipher text is prevented from being displayed on the terminal beyond the character code area, and a cipher text of the same length as the original text is generated. In particular, in encrypting a string to be treated as a computer terminal in a multi-step procedure based on mathematical operations, some bits of the multilingual character code are fixed and only the remaining bits are encrypted to perform encryption. Character code region to be restricted within the region of fixed bits.

The multi-language code is a character code defined as two bytes or more in order to handle international languages such as Korean and Japanese in a computer terminal, and is provided by a national standard code such as KSC5601 or a software company such as Microsoft. Character codes, Unicode to standardize all languages.

In addition, the bit masking means that a bit value of a specific position is blocked in a character code, and a bit value of a necessary place is passed as it is, and a bit value of an unnecessary place is blocked. Mathematically, this bitwise operation can be implemented as an AND operation. Referring to Table 1 below, if the original bit is ANDed with 0, the original bit is output as 0 regardless of the original value, and if the original bit is ANDed with 1, the same value as the original bit is output. This concept can be used in the following cases: If you want to remove the upper 4 bits from 1 byte and use only the lower 4 bits, you can perform an AND operation with the upper 4 bits as 0 and the lower 4 bits as 1. That is, a bit mask such as "00001111" may be applied to the original by AND operation.

On the other hand, the encryption is a symmetric cryptographic algorithm in the technical field of the present invention, the mathematical theory of the symmetric cryptographic algorithm implemented by a computer terminal is based on the XOR operation shown in (Table 2). Simply performing an XOR operation on each bit of the original text with each bit of the secret key can produce a successful ciphertext. The generated cipher text can be obtained by reversing the secret key used for encryption as shown in Equation (1). The name symmetric is due to the use of the same secret key for encryption and decryption. Many symmetric algorithms have been introduced that add the characteristics of XOR operation and procedures such as diffusion and substitution to enhance security. The representative ones are DES algorithms that are widely used around the world and SEED algorithms developed and standardized in Korea. There is this.

Hereinafter, a detailed description of a preferred embodiment of the present invention will be described with reference to the accompanying drawings. In the following description, detailed descriptions of well-known functions or configurations will be omitted when it is determined that the detailed descriptions of the known functions or configurations may unnecessarily obscure the subject matter of the present invention.

In an embodiment of the present invention, in order to provide a function of correcting an encryption result of a multilingual text string such as Korean and Japanese handled by a computer terminal into a character code that can be displayed on a terminal, the character code is divided into a plurality of bit masking groups. After calibrating the secret key with the bit mask corresponding to each group, encryption is performed.

In general, there are two types of encryption algorithms used in computer terminals. One is a symmetric algorithm that is mainly used for encrypting data such as files and packets, and the other is an asymmetric algorithm that is mainly used in authentication systems such as financial certificates. to be. However, the symmetric algorithm currently used is simply an algorithm for encrypting binary data. Therefore, if a text string is encrypted, it cannot be output to the terminal beyond the character code area and can not be saved in the form of a text file. . Algorithms have been developed to compensate for this problem, but the problem that the encryption result is longer than the original length is again exposed.

Accordingly, the present invention proposes a method of correcting the encryption result so as not to deviate from the character code area so that it can be displayed on the terminal, stored in the form of a text file, and kept in the same length as the original text.

First, the method of the present invention will be described with reference to FIG.

1 is a view showing that when multilingual codes such as Korean and Japanese are encrypted with an arbitrary secret key according to an embodiment of the present invention, the result may be out of the corresponding code area.

Referring to FIG. 1, when the multi-language code region, which is the original region 101, is encrypted with an arbitrary secret key region 102, the resulting ciphertext region 103 may be out of the original region 101. Giving.

The original text area 101 is a multi-language code area such as Korean and Japanese. Here, the Korean language area of the KSC5601 code is taken as an example.

In general, in displaying a text string in a computer terminal, an ASCII code using the lower 7 bits of a byte is used for alphabets, numbers, and basic symbols. However, multi-byte notation, such as Korean, Japanese, Chinese, and Arabic, uses two bytes or more codes.

For example, an English letter 'A' requires one byte, and the corresponding code is defined in the ASCII code table as '01000001'. '01000001' is the binary representation of the corresponding bit, which is equivalent to '41' when converted to hexadecimal hexadecimal notation, which is commonly used.

On the other hand, two bytes are required to indicate Korean 'ga', and the corresponding code is '1011000010100001', which is defined in the KSC5601 Korean code table. Likewise, converting to hexadecimal hexadecimal notation corresponds to 'B0A1'. As such, all multilingual languages are defined and represented in two or more code tables.

Since the secret key area 102 is defined as an arbitrary area, it may have all areas of '0000' to 'FFFF' in hexadecimal hexadecimal notation. The secret key can be directly input by the keyboard, which is a terminal of a computer terminal, or can be read from a file stored in an external storage device such as a CD or a USB memory. Can be defined.

The ciphertext area 103 is an area that may be occupied by a result of encrypting the original text area 101 and the secret key area 102 with the symmetric key encryption algorithm 104. Although the original text area 101 is limited to a string code area of a specific multilingual language, but the secret key area is not limited, it is shown in FIG. 1 that the cipher text area 103 which is a result of the encryption may be out of the original text area 101. have. In general, symmetric key encryption algorithms such as DES include an XOR operation internally, and the operation does not guarantee that the result of encrypting the original region 101 does not leave the original region. In addition, in order to enhance security, algorithms such as DES, etc. are further difficult to be guaranteed because the original region 101 is added in addition to the XOR operation. Therefore, there is a need to fix some bits of the original text area so that the cipher text area 103 does not leave the original text area 101.

In Example 1 of Table 3, since the character code of the result of encryption is not defined in the computer terminal, it is simply output as '?' To the terminal of the computer terminal. Of course, if the code is stored as a binary file without being output to the terminal of the computer terminal, the code can be valid internally, but the output from the viewer program, the editor, the word processor, etc., which reads the contents of the text file, impossible.

In case 2, the result of encrypting Hangul is output in Hanja, outside the Hangul domain. The output of Chinese characters is not a problem, but because Chinese characters are used in Chinese and Japanese Windows, and their code areas are different, the result of the encryption of Korean characters violates the range of Chinese characters. There are potential problems.

In Cases 3 and 4, the result of encrypting Hangul is output as 2 bytes of ASCII characters. There is no big problem, but it does not seem so desirable that the result of encrypting a two-byte multilingual code changed to two one-byte codes.

As a result of examining cases 1 to 4, it was found that the encryption of the string should be encrypted in the character code area that can be displayed on the terminal, and it is preferable that the character code area is converted in the same language code area. Could see.

Table 4 below shows the KS5601 Korean code table for reference as a specific embodiment of the present invention.

The symmetric key encryption algorithm 104 is an algorithm using the same secret key in encryption and decryption, and the mathematical basis of the symmetric key encryption algorithm 104 in a computer terminal is based on an XOR operation. Standardized algorithms such as DES and SEED are also internally based on XOR operation, and are made up of additional procedures such as confusion and substitution to enhance security. In the embodiment of the present invention, in order to clearly illustrate the object of the present invention, the symmetric key encryption algorithm is replaced by simply performing an XOR operation. Only an XOR operation can be used to generate a successful ciphertext.

2 is a diagram illustrating a method of dividing an original text into a plurality of bit masking groups so that the code region of the cipher text does not leave the code region of the original text, and correcting a secret key with a bit mask corresponding to each group according to an embodiment of the present invention. One drawing.

Referring to FIG. 2, the text area 210 is divided into three bit masking groups, and the first bit masking group 211 is encrypted using a secret key 221 masked with a bit mask of the group. It does not leave the first region 231 of the region 230. In this manner, the second bit masking group 212 and the third bit masking group 213 are also guaranteed not to leave the original region.

The criterion for dividing into multiple groups is the commonality of the higher bits. Referring to (Table 5) below, the upper 4 bits of the upper byte and the upper 3 bits of the lower byte are common in Korean 'ga' to 'we'. That is, the criteria for distinguishing characters from 'a' to 'we' are determined by the lower 4 bits of the upper byte and the lower 5 bits of the lower byte. Here, although the second bit is not common among the upper 3 bits of the lower byte, if only some bits in the middle are masked, there may be confusion. Therefore, the upper 3 bits are combined and the lower 5 bits are encrypted.

Therefore, in order to ensure that the result of encrypting the original text contained in this range does not fall outside this range, the common upper bits are kept intact and only the lower bits need to be encrypted.

In this way, other areas of Hangul can be corrected so as not to be out of the area, and other multilingual codes such as Japanese and Chinese can be preserved by encrypting only the lower bits after grouping by common bits. have.

3 is a view showing an embodiment in which some bits are fixed and only the remaining bits are encrypted according to an embodiment of the present invention.

Referring to FIG. 3, as a method of a specific embodiment for fixing some bits and encrypting only the remaining bits, the fixed bit 311 of the upper 1 byte of the original text and the fixed bit 312 of the lower 1 byte are It is shown that the bit 351 of the same position of the upper 1 byte of the ciphertext is the same as the bit 352 of the same position of the lower 1 byte.

In order to make this result, in the method of FIG. 3, the embodiment of the present invention encrypts a specific group 310 of the original text region with the new secret key region 340, which computes the secret key region 320 with the bit mask 330. The procedure is shown. In this example, the symmetric key encryption algorithm simply performs XOR operation. Therefore, if there is a bit to be fixed, the bit may be calculated as '0'. As a characteristic of XOR operation, '0' and the bit operated on are retained. For reference, the bit calculated with '1' has the opposite value. Therefore, if the position of the bit to be fixed is masked, the secret key is filtered with the mask, and the encryption operation is performed with the filtered secret key, the masked bits are fixed and only the unmasked bits are encrypted.

Herein, the specific group 310 of the original region is one of the bit masking groups divided in FIG. 2 and shows region 1 shown in Table 5 as a specific example. The method for fixing some bits and encrypting only the remaining bits can be variously implemented due to a problem in the program implementation. Here, an example is simply shown as a method of bit masking a secret key. It is only one example to help understand, and it is noted that the method of this example is not a patent claim.

The specific group of the text area 310 is composed of a total of two bytes, that is, an upper one byte and a lower one byte, and the upper one byte is composed of a common upper four bits 311 and lower four bits separating each character. In addition, the lower one byte is composed of a common upper three bits 312 and the lower five bits separating each character.

Here, although the second bit is not common among the upper 3 bits of the lower 1 byte, confusion may occur when only some bits in the middle are masked. Therefore, the upper 3 bits are grouped together and only the lower 5 bits are encrypted.

Table 6 shows specific examples corresponding to FIG. 3. In case 1, when the XOR operation is performed with the secret key 'ab' in Korean, the result is out of the character code area, and is displayed as '?' In the terminal of the computer terminal. To solve this problem, Case 2 shows the result of correction by applying bit masking. In case 2, if the hexadecimal hexadecimal code '61 62 'of the secret key' ab 'is bit masked and corrected with the bit mask' 0F 1F ', the result of encrypting' high 'is' 굻'.

4 is a flow chart for performing an encryption procedure by receiving an original text and a secret key according to an embodiment of the present invention.

4 shows an example of how the present invention can be applied to an existing symmetric key encryption algorithm, and this flowchart itself is not included in the claims.

Referring to FIG. 4, when encryption of the original text is requested through the computer terminal, the original text and the secret key are input in a string array (step 401).

The input text is sequentially read one byte at a time (step 402) and the procedure is encrypted while repeating the procedure until the end of the string becomes NULL (step 410). As in the original text, the secret key is read one by one sequentially (step 402) and repeatedly used.

If the original code read sequentially falls within the ASCII code range, branches to the procedure of applying the ASCII encryption function (step 404), and if it does not fall within the ASCII code range, reads an additional one byte of the original text (step 406). In step 403, the process proceeds to applying the multilingual encryption function (step 407).

The ASCII encryption function (step 404) describes the detailed steps in FIG.

The multilingual encryption function (step 407) describes the detailed steps in FIG.

When the ASCII encryption function is completed (step 404), the index is incremented by one (step 405) to read the next byte of the original string.

When the multilingual encryption function (step 407) is complete, the index is incremented by two (step 408) to read the next byte of the original string.

Since the secret key string length is different from the original string length, an index for reading the next byte of the string must be managed separately. In general, if the secret key string has been read to the last byte, the index is incremented by repeatedly reading the first byte.

If the encryption is completed to the last byte of the original text string, the generated cipher text is output (step 411).

FIG. 5 is a flowchart of a sub procedure of FIG. 4 according to an embodiment of the present invention, in which an encryption procedure is performed when a corresponding character is an ASCII code while reading a string of original text one byte.

Referring to FIG. 5, when the original 1 byte and the secret key 1 byte are read (step 510), if the original 1 byte corresponds to an area that does not need encryption or should not be encrypted (step 520), the encryption procedure is performed. Instead of performing it, the original 1 byte is substituted into the encrypted text 1 byte as it is (step 570).

If the original 1 byte corresponds to a region between any C3 to C4, the bit mask 551 defined for use in the region is bit masked (step 550).

The bit masked secret key 581 is used to encrypt one byte of the original text using a symmetric key encryption algorithm (step 580). For the sake of clarity and clarity, the symmetric key encryption algorithm is replaced by simply performing an XOR operation.

In this way, a bit is defined as a bit mask defined for each case where the original one byte is a region between C5 and C6, and a region between generalized Cn and Cn + 1 (n = 1, 3, 5, ...). After masking, an encryption procedure is performed.

FIG. 6 is a sub-procedure of FIG. 4 according to an embodiment of the present invention. When a character string is a multi-language code while reading a character string of the original text by one byte, a flowchart of performing an encryption procedure after additionally reading one byte. to be.

Referring to FIG. 6, when the original 2 bytes and the secret key 1 byte are read (step 6010), if the upper 1 byte of the original text does not need encryption or corresponds to an area that should not be encrypted (step 6020), the encryption procedure is performed. 2 bytes of the original text are substituted into 2 bytes of the cipher text without performing (step 6070 and 6110).

If the upper 1 byte of the original text corresponds to a region between any C3 to C4, a bit mask (6051) defined for use in the region is bit masked (step 6050).

A bit masked secret key 6061 is used to encrypt the upper 1 byte of the original text using a symmetric key encryption algorithm (step 6080).

In addition, in order to encrypt the lower 1 byte of the original text, a bit mask (6091) defined for use in the corresponding area is bit masked (step 6090).

With the bit masked secret key 6121, the lower 1 byte of the original text is encrypted using a symmetric key encryption algorithm (step 6120). For the sake of clarity and clarity, the symmetric key encryption algorithm is replaced by simply performing an XOR operation.

In this way, the upper 1 byte of the original text is defined as the bit mask defined for the area between C5 and C6, and for the area between generalized Cn and Cn + 1 (n = 1, 3, 5, ...). After bit masking, an encryption procedure is performed.

Table 7 below shows an example of applying KSC5601 Korean alphabet by applying the method of the present study. First, it shows the problem when only XOR operation is performed, and next shows the problem when encrypting with DES algorithm. Finally, it shows the successful result when it is supplemented by the method of this study.

On the other hand, in the embodiment of the present invention has been described with respect to specific embodiments, various modifications are possible without departing from the scope of the invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be defined not only by the appended claims, but also by those equivalent to the claims.

According to the present invention, by providing a method for correcting an encryption result for a multilingual text string such as Korean and Japanese handled by a computer terminal with a character code that can be displayed on a terminal, the encryption result can be stored in a text form instead of a binary file. can do. Being able to save in the form of text means that it can be stored in encrypted form even in an e-mail body, an Internet bulletin board, a messenger, a word processor, etc., and can be printed as a paper document if necessary. In addition, since the present invention encrypts an encryption result of a multilingual text string code such as Korean and Japanese within the same code area, the length of the original text and the cipher text can be the same.

If the result of the encryption can be displayed on the terminal and has the same length as the original text, the security management of the computer system can be more efficiently operated.

For example, the present invention can be effectively used as a method for preventing the leakage of customer information, which has become a social issue recently. Customer information can be leaked by accessing the database or hacking communication packets. Therefore, it is necessary to encrypt and manage customer information. By using the present invention, the cost burden of modifying the field length of a database or a communication packet can be reduced. In addition, since the encryption result is maintained in the text string code area of the original text, the encrypted result can be stored in the database as it is. In order to monitor the communication packet, the system operator should leave the log in the form of a text file. The log is left in the text string code area of the encrypted original text, so that it can be monitored clearly. If the existing encryption algorithm is used, it may be out of the character code area, so it is inconvenient to check the log such as unnecessary characters left in the log or line breaks caused by the control characters.

In addition, since the mobile phone SMS text message is limited to 80 characters, the result of encrypting the original 80 characters should not be more than 80 characters. However, using the present invention, there is an advantage that can convert the original text of 80 characters to the cipher text of 80 characters. The possibility of eavesdropping on voice calls and text messages on mobile phones, which have been hidden in public for political reasons, has already turned out to be true. With the present invention, even national secrets, corporate secrets, and personal private secrets can be safely transmitted as text messages. This is possible.

Claims (4)

In the method to complement the symmetric key encryption algorithm for text strings, In encrypting a string treated as a computer terminal by a multi-step procedure based on a mathematical operation, a process of fixing some bits of the multilingual character code and performing encryption only on the remaining bits; Complementary method for symmetric key cryptographic algorithms. In claim 1, The text string may include a character array defined to be displayed on a terminal of a computer terminal with reference to the defined character code table and to be input, output, deleted, and stored in a text editor such as a notepad. How to complement the symmetric key cryptographic algorithm for a text string. In claim 1, A symmetric key cryptographic algorithm is a process of performing encryption by a multi-step procedure based on a mathematical operation, and the algorithm security method is complementary to a symmetric key cryptographic algorithm for a text string, which is inserted in the middle of the various steps of the symmetric key cryptographic algorithm. Way. In claim 1, Multi-language character codes are character codes defined to handle international languages such as Korean and Japanese on computer terminals, and standardize national standard codes such as KSC5601, character codes provided by software companies such as Microsoft, and all multilingual languages. A unicode; complementary symmetric-key cryptographic algorithm for a text string.

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