WO2018100246A1

WO2018100246A1 - Method and arrangement for encrypting data

Info

Publication number: WO2018100246A1
Application number: PCT/FI2017/050841
Authority: WO
Inventors: Sam WIDLUND
Original assignee: Widlund Sam
Priority date: 2016-11-30
Filing date: 2017-11-29
Publication date: 2018-06-07
Also published as: FI20165911A; FI20165911L

Abstract

Method and arrangement for encrypting data with an apparatus, in which the encrypted data is formed from the plaintext content to be encrypted, a predefined amount of data at a time, by means of an encrypting bit or bit pattern (Y_n) to be formed for each individual bit or individual bit pattern. The encrypting bit or bit pattern (Y_n) of the plaintext bit or bit pattern (D_n) is formed by means of an encryption key. which encryption key (203, 204, 300, 400) comprises at least two encryption tables (A, B, C) to be used in the encryption, which encryption tables have a different number of elements (a1...a7, b1...b5, cl...c3) to each other, which elements comprise randomly formed data. The plaintext bit or bit pattern (D_n), the encrypting bit or bit pattern (Y_n) and the elements (al...a7, bl...b5, cl...c3) of the encryption table are of the same length as each other, e.g. one byte in length. An encrypting bit or bit pattern (Y_n) is formed by selecting one predefined element from each encryption table (A, B, C) to be used in encrypting on the basis of the sequence number (n) of the bit or bit pattern to be encrypted, and by performing an XOR operation between all these selected elements. In the method, the encrypted bit or bit pattern (CB_n) is formed by performing XOR operations between the plaintext bit or bit pattern (Dn) to be encrypted and the encrypting bit or bit pattern (Y_n) that is formed.

Description

METHOD AND ARRANGEMENT FOR ENCRYPTING DATA

Field of the invention

The invention relates to a method and to an arrangement, by means of which data is encrypted with a device and/or with software on a device, e.g . for send ing or record ing it safely.

Background of the invention

Known in the art are various encryption systems with which messages or data a re encoded in such a way that only authorized parties ca n read them . Encryption does not prevent the interception of messages, only the read ing of them . An encryption system converts the plaintext of a message or data into ciphertext using an encryption algorithm . After this, the message or data can only be read if the encryption of the ciphertext is decrypted . In principle, it is possible to decrypt the encryption without the key, but very much computing power is needed to do this if the encryption system is implemented well . The authorized recipient can easily decrypt the message with the encryption key that the sender of the encrypted message gave to him/her. One example encryption solution known in the art is a symmetrical encryption method . In symmetrical encryption, both the sender and the recipient have the same information about a secret key. It can be that the sender and the recipient use the secret key in a d ifferent format, but both can if they so wish manage the key used by the other party with an algorithm effectively calculable from their own .

The widely used encryption methods nowadays are based on the fact that breaking them with other than a brute-force-type method wou ld requ ire the solving of a certain mathematical problem . Confidence in encryption in modern systems is based, therefore on the belief that no- one has invented how to break the encryption algorithm with a reasonable and effective method needed to solve the mathematical problem, i.e. in such a way that that in practice it is solvable within a finite period of time.

Of the encryption solutions known in the art, only the one-time key encryption mechanism has been proven to be a theoretically unbreakable encryption method. The one-time key encryption mechanism, however, has so many problems in terms of its practical use that it is hardly ever used. A problem with other encryption algorithms known in the art is that their reliability against attempts to break them cannot be proven mathematically.

Brief description of the invention The aim of this invention is to provide a new type of method and arrangement for arranging the encryption of data with a device, with an apparatus and/or with software to be executed on a device e.g. for the recording of data or for telecommunications in data format. The encryption method according to the invention is characterized by what is stated in the characterization part of claim 1. The encryption method according to the invention is also characterized by what is stated in claims 2 - 22. The arrangement according to the invention is characterized by what is stated in the characterization part of claim 23 relating to the arrangement. The arrangement according to the invention is also characterized by what is stated in the characterization part of claim 24 relating to the arrangement.

In the solution according to the invention, information or data is encrypted with an apparatus in a software-based manner, in an apparatus-based manner, or in a manner combining these. In the solution according to the invention, the encrypted data is formed from the plaintext content to be encrypted, a predefined amount of data in length at a time, by means of an encrypting bit or bit pattern, such as an encrypting byte, to be formed for each individual bit or individual bit pattern, e.g . for each byte, individually. In the solution of the invention, the amount of data to be processed at a time (e.g. a plaintext byte, an encrypting byte, a historical byte and an encrypted byte) can be formed from a certain number of bits or bytes.

In the solution of the invention, there are randomly generated data bits or bit patterns in encryption tables, and the algorithm proceeds systematically in such a way that a sequence of sufficient length is obtained during which the encryption does not repeat itself. In one embodiment of the invention, in the encryption algorithm the one-time encrypting bit or bit pattern Y_n is formed by calculation from a plurality of random numbers in such a way that the same sequence is repeated so seldom that the length of the message to be encrypted is shorter than the sequence generated by the algorithm.

In the solution of the invention, the encrypting bit or bit pattern Y_n of the plaintext bit or bit pattern D_n is formed by means of an encryption key, which encryption key comprises at least two encryption tables, which encryption tables have a different number of elements to each other, e.g . in such a way that the largest common factor of the number of elements of any two encryption tables whatsoever is 1, and which elements comprise randomly formed data. The elements of an encryption table are of the same length as each other, e.g. the length of a byte.

An encrypting bit or bit pattern Y_n is formed in the solution according to the invention by selecting one predefined element from each encryption table on the basis of the sequence number n of the bit or bit pattern to be encrypted, and by performing an XOR operation between all these selected elements. In the method, the encrypted bit or bit pattern CB_n, such as a byte, is formed by performing an XOR operation between the plaintext bit or bit pattern D_n to be encrypted and the encrypting bit or bit pattern Y_n that is formed, e.g. between the byte to be encrypted and the encrypting byte formed.

In the solution of the invention, after encrypting one bit or bit pattern, such as a byte, the next bit or bit pattern can be encrypted by selecting the next plaintext bit or bit pattern, and by forming an encrypting bit or bit pattern on the basis of the next elements of the encryption tables. In one embod iment of the invention, the lengths of the encryption tables are d ifferent prime numbers to each other.

In the solution of the invention, an element of an encryption table of an encryption key is one or more randomly selected bits or one or more randomly selected bytes, wherein the lengths of the encrypting bit or bit pattern, plai ntext bit or bit pattern and/or encrypted bit or bit pattern correspond to the length of the element of the encryption table. In one embod iment of the invention, encrypted data is formed from the plaintext content to be encrypted, a predefined amou nt of data in length at a time, by means of an encrypting bit or bit pattern Y_n to be formed for each ind ivid ual bit or ind ivid ual bit pattern, and add itionally also by mea ns of a historica l bit or bit pattern H_n.

The solution of the invention can be utilized for arrang ing data encryption in a digital data transmission network, in which the data transmission network comprises at least two devices, of which the first device is at least a sender and the second device at least a recipient. The data to be sent is encrypted by means of an encryption key and the encrypted data is sent to another device. Correspond ing ly, with the other device the encrypted data received is decrypted utilizing the same encryption key as in encrypting the data . Another target application of the method and arrangement according to the invention, alongside messag ing, is mass memories, in conjunction with which large volumes of sensitive data are processed . In such a case, the data intended for record ing is encrypted by means of an encryption key before record ing the data e.g . in mass memory.

One advantage of the solution of the invention is that by means of it encryption can be implemented effectively and securely, in which case the solution accord ing to the invention enables the safe record ing of data or the safe transmission of data and messages via an u ntrusted commu nication channel . By means of solution accord ing to the invention, the number and length of the encryption key tables used as the encryption key of the algorithm can be adjusted to be whatever desired, in which case effective performance of encryption can be adjusted compared to the computing power needed to break the encryption.

Brief description of the figures

In the following, the invention will be described in more detail by the aid some examples of its embodiment with reference to the drawings 1 - 5, wherein

Fig. 1 presents a functional diagram of a solution according to one embodiment of the invention;

Fig. 2 presents the use of the solution according to one embodiment of the invention in the data encryption of a data transmission;

Fig. 3 presents an example of an encryption key according to one embodiment of the invention;

Fig. 4 presents an example of an encryption key according to another embodiment of the invention;

Figs. 5A and 5B present the values of simulated encrypted data of a solution according to one embodiment of the invention.

Detailed description of the invention

The idea of the method to be used in the solution of the invention is that an encryption key is used that is formed from a number of encryption tables, the elements of which contain randomly generated data. The number of encryption tables is at least 2, in some embodiments e.g. at least 3 or 4. The sender and recipient have in their use the same encryption keys, i.e. the same encryption tables. The encryption algorithms according to the invention utilize the properties of the encryption keys described above. By means of the solution of the invention, encryption can be implemented effectively and securely. Thus, the solution according to the invention can enable the safe recording of data or the safe transmission of data and messages via an untrusted communication channel.

Fig. 1 presents a schematic view of the operation associated with the data encrypting of one embodiment of the invention. In the solution according to the invention, information or data is encrypted with an apparatus in a software-based manner, in an apparatus-based manner, or in a manner combining these. In the solution according to the invention, encrypted data is formed from the plaintext content to be encrypted, a byte or some other predefined amount of data in length at a time, by means of an encrypting byte (Y_n) to be formed for each individual byte or for each individual bit or individual bit pattern. In the embodiments described below, a byte is used as an example of the predefined length of the amount of data to be processed at a time, but the length of the data to be processed at a time in the embodiments below can, instead of a byte, be e.g. a certain number of bits or a certain number of bytes. In the solution according to the invention, a plaintext bit or bit pattern, an encrypting bit or bit pattern, a historical bit or historical bit pattern, an encrypted bit or bit pattern and the elements of the encryption tables are of the same length, i.e. a number of bits or bytes that is of a certain length. In the solution of the invention, the encrypting byte Y_n of the plaintext byte D_n is formed by means of an encryption key, which encryption key comprises at least two encryption tables, which encryption tables have a different number of elements to each other, e.g. in such a way that the largest common factor of the number of elements of any two tables whatsoever is 1, and which elements comprise randomly formed data. An encrypting byte Y_n is formed by selecting one predefined element from each encryption table on the basis of the sequence number n of the byte pattern to be encrypted, and by performing an XOR operation between all these selected elements. In the method, the encrypted byte CB_n is formed by performing an XOR operation between the plaintext byte D_n to be encrypted and the encrypting byte Y_n that is formed. In the solution of the invention, after encrypting one byte, the next byte can be encrypted by selecting the next plaintext byte and by forming an encrypting byte on the basis of the next determined elements of the encryption tables and on the basis of the sequence number of the byte.

The encrypting byte Y_n can be formed e.g. as follows:

Y_n= A[n mod |A| ] 0 B[n mod | B| ] 0 ... 0 N[n mod | N | ]], where A[n mod |A| ] is the element intended for the byte in the sequence n of the first encryption table,

B[n mod | B| ] is the element intended for the byte in the sequence n of the second encryption table, and

N[n mod | N | ] is the element intended for the byte in the sequence n of the Nth encryption table.

In the solution of the invention, the sequence of XOR operations has no significance. In the above example, the modulo operation used is a remainder from division. In one embodiment of the invention, the lengths of the encryption tables are different prime numbers to each other.

In the solution of the invention, an element of an encryption table of an encryption key is one or more randomly selected bits or one or more randomly selected bytes, wherein the lengths of the encrypting byte, the plaintext byte and/or the encrypted byte correspond to the length of an element of an encryption table.

In one embodiment of the invention, in the method a starting point is determined, i.e. each encryption table has its own starting element from which the encryption is started. The starting point can be a constant, e.g. the index 0 in each encryption table. The starting point can also be specific to the key, e.g. there can be for each encryption table an own randomly drawn point which is known to the sender and to the recipient.

In one embodiment of the invention, encrypted data is formed from the plaintext content to be encrypted, a byte at a time, by means of also a historical byte H_n in add ition to an encrypting byte (Y_n) to be formed for each ind ividual byte.

If a historical byte is used in the encryption, the encrypted byte CB is formed by forming an XOR operation between the historical byte, the encrypting byte Y and the data D to be encrypted . The starting value of the historical byte can be determined on the basis of the starting point and of a predefined, possibly key-specific, random constant. A historical byte H_n can be formed e.g . by selecting one predefined element from one predefined encryption table on the basis of the sequence number n of the byte to be encrypted and the encrypting byte Y_n, a nd by forming an XOR operation between the selected element a nd the historical byte H_n-i of the previous byte to be encrypted . In one embod iment, the encrypted byte CB_n is formed by performing XOR operations between the plaintext byte D_n to be encrypted, the encrypting byte Y_n that is formed and the historical byte H_n that is formed . In one embod iment of the invention, there can be more than one historical byte. If there is more than one historical byte, i n one embod iment of the invention, some of the historical bytes can be formed i n such a way that a historical byte corresponding to the previous one is not used . If there is more than one historical byte, in one embod iment of the invention some of the historical bytes can be formed at least on the basis of the sequence number n of the byte to be encrypted .

In one embod iment of the invention, when forming a historical byte, instead of an encrypting byte Y, a predefined number of elements can be selected from some of the encryption tables on the basis of the sequence number n of the byte to be encrypted, and by performing an XOR operation between all these selected elements. In the solution of the invention, e.g . in all the points mentioned in the application, instead of an XOR operation, another operation that connects two bytes can be used in such a way that the sequence of bytes is of no significance and the result of the operation between two random bytes is also random, e.g. 'not XOR'.

In one embodiment of the invention, the encrypted data is sent from the sending device via a data network or telecommunications connection to the receiving device. The receiving device decrypts the encryption of the encrypted data received, a byte at a time, by means of the encryption key. The receiving device can decrypt the received data a byte at a time e.g. as follows:

D_n = Y_n Θ H_n Θ CB_n, where

- CBn (crypted byte) is the encrypted byte from the sequence n,

- Yn is the byte from the sequence n generated from the encryption key of the algorithm,

- Hn is the historical byte of byte n, and

- D_n is the plaintext byte from the sequence n received.

In one embodiment of the invention, the encrypted data is recorded in the memory means of the device, such as in mass memory. In this embodiment, the encryption of the data can be decrypted in the manner presented in the preceding.

The invention also relates to an arrangement for encrypting data with a device or with an apparatus. The arrangement comprises means arranged for the device for recording and managing an encryption key, means for performing data encryption and for decrypting encryption with an encryption key. The arrangement is adapted to form encrypted data from the plaintext content to be encrypted, a byte at a time, by means of an encrypting byte Y_n to be formed for each individual byte, wherein the byte is formed from a certain number of bits or bytes. The arrangement is adapted to form the encrypting byte Y_n of the plaintext byte D_n by means of an encryption key, which encryption key comprises at least two encryption tables, which encryption tables have a different number of elements to each other, e.g. in such a way that the largest common factor of the number of elements of any two tables whatsoever is 1, and which elements comprise randomly formed data. The arrangement is adapted to form an encrypting byte Y_n by selecting one predefined element from each encryption table on the basis of the sequence number n of the byte to be encrypted, and by performing an XOR operation between all these selected elements. The arrangement is adapted to form the encrypted byte CB_n by performing XOR operations between the plaintext byte D_n to be encrypted and the encrypting byte Y_n that is formed.

In one embodiment of the invention, the encryption method according to the invention can be used for encrypting telecommunications or for recording data. This kind of arrangement can e.g. comprise devices transferring data with each other, e.g. devices and/or servers messaging with each other on a data transmission network.

Fig. 2 presents a schematic view of one embodiment of the arrangement according to the invention. The arrangement and method according to the invention can be used for arranging data encryption in a digital telecommunications network according to the symmetrical encryption model. The data transmission network can be wired or wireless, such as e.g. an IP network, the Internet, an Intranet, LAN, WLAN, CDMA, TDMA, FDMA or Bluetooth.

The data transmission network comprises at least two devices 201, 202 communicating with each other, of which one of the devices functions at least as a sender and the other of the devices at least as a recipient. Messaging between the devices is in data format, such as the transmission of messages, files and/or emails, or e.g. a video and/or audio file, and/or video and/or audio streaming.

In one embodiment of the invention, arranged for the devices 201, 202 are means for recording and managing an encryption key 203, 204, means for performing data encryption and/or decrypting encryption with a selected algorithm and an encryption key. These means can be arranged e.g. by means of a program or corresponding instruction set to be implemented in a processor environment, by means of which encryption keys are managed, encryption keys are distributed and/or the encryption and/or decryption of data is performed. Means for reading, recording, receiving and/or sending data can also be arranged in the device. The device to be used in the arrangement according to the invention can be any device whatsoever recording and/or sending and receiving data, e.g. a computer, a portable device, a server or a corresponding device for which resources for managing and/or distributing encryption keys, and/or for encrypting data and/or decrypting data, are arranged by means of the solution according to the invention. For example, a database for the encryption keys can be arranged in the memory area of the device, with commands to be executed in the manner of a program in the processor environment of the device.

In the solution according to the invention, there is data intended for e.g . recording and/or transmitting, which data can be e.g. a message, a file, a video and/or data file, and/or a video and/or audio stream. When the data has been produced and/or it is desired to encrypt it, the device selects a predefined starting place from an encryption key arranged in memory, and by means of the encryption key starts to encrypt the message according to the method of the invention. If the encryption key has been recorded on the device encrypted, its encryption is decrypted. Encryption of the data to be sent can be performed with the processor means of the device by executing an encryption algorithm according to the solution of the invention. After encryption, the encrypted data can, if so desired, be recorded and/or sent to a recipient via a data network. If the encrypted data is sent via a data network, the device receiving the message receives the message and selects a predefined starting place from an encryption key arranged in memory, and after this starts to decrypt the data of the encrypted message by means of the encryption key.

In one embodiment of the invention, the same encryption key is not used more than once, so that if the device that received the data in the aforementioned example wants to respond to the device that sent the encrypted message, both devices use a new encryption key when the recipient of the first message sends data to the sender of the first message. Fig. 3 presents an example of an encryption key 300, which is formed from three encryption tables. According to the solution of the invention, the lengths of the tables are of different magnitudes to each other, and here the lengths of the tables are prime numbers; 7, 5 and 3 in the embodiment of Fig. 3. For enabling reliable encryption, it would be advantageous if the lengths and/or number of the tables were larger, but the example of Fig. 3 presents the basic idea of the structure of an encryption key and of an encryption table of an encryption key. In the example of Fig. 3, the encryption key 300 thus comprises encryption tables A, B, C. In encryption table A there are seven elements al ...a7, in encryption table B there are five elements bl ...b5, and in encryption table C there are three elements cl...c3. The encryption key is recorded in the device in which it is desired to encrypt data and/or decrypt data. In each element of a table is a randomly formed byte. In one embodiment of the invention, there can also be a predefined number of randomly formed bits or bytes in each element.

Fig. 4 presents another example of an encryption key 400, which is formed from only one table, wherein the position of each encryption table A, B, C in this one table is known. This embodiment otherwise corresponds to the example of Fig. 3 but can be more effective to implement in some devices because only one table is needed in it. It is predefined in the arrangement between which elements of the table certain encryption tables (i.e. certain elements of the encryption tables) are located. In the example of Fig. 4, the elements of encryption table A are located in the elements 1 - 7 of the table of the encryption key, the elements of encryption table B are located in the elements 8 - 12 of the table of the encryption key, and the elements of encryption table C are located in the elements 13 - 15 of the table of the encryption key.

Instead of encrypting an individual byte, therefore, also a certain predefined number of bits or bytes, e.g . four bytes, can be encrypted at a time. In such a case, the values of the elements of the encryption tables must be of corresponding lengths, i.e. in the aforementioned case, each must be four bytes in length.

Figs. 5A and 5B present the values of simulated encrypted data of a solution according to one embodiment of the invention. The data that is encrypted is, in this example, a simple zero. In the example of Fig. 5A, 10 mb of data have been encrypted and the figure presents the values of the encrypted data. In Fig. 5B, the lOmb of data has been encrypted a second time partly with a different key, and the second encryption instance is compared in Fig. 5B to the data encrypted earlier (which is also presented in Fig. 5A). By means of the simulations, it can be seen that the data encrypted by means of the solution according to the invention is different in different instances, and in the encrypted data there is visually no correlation between different encryption instances.

In the following, one solution according to the present invention is presented, in which solution the encryption key comprises six encryption tables (A, B, C, D, E and F). In the solution of the invention, the lengths of the encryption tables are arranged to be of different sizes in such a way that the largest common factor of the lengths of any two tables whatsoever is 1. This can be implemented e.g. in such a way that the lengths of the encryption tables are different prime numbers. The lengths of the encryption tables can be e.g. from a few hundred bytes to some kilobytes.

The encryption method according to the invention comprises a predefined starting point, i.e. each encryption table of an encryption key has its own index from which the encryption is started. The starting point can be a constant, e.g. the index 0 in each encryption table, or it can be specific to the key, e.g. each encryption table has its own randomly drawn point which is known by the sender and to the recipient.

From the starting point (e.g. encryption table A index/element 1, B index/element 22, C index/element 213, etc.) one value of a byte is calculated in a predefined manner, the value depending on all the values of the element according to the indexes of the starting point of the encryption tables A - F. In one basic embodiment of the invention an XOR operation is formed between the selected elements of the encryption tables, e.g. A[al] 0 B[bl] 0 C[cl] 0 D[dl] 0 E[el] 0 F[fl], where al, bl, cl, dl, el and fl are the values of the starting points of the encryption tables in question. In one embodiment of the invention, it is possible to determine a historical byte H in addition to an encrypting byte Y. The historical byte can be determined from the previous determined starting point and from a predefined, possibly key-specific, random constant. The sender and recipient of a message can agree that the historical byte is calculated e.g. from a certain encryption table, e.g. from table C, by selecting from the table chosen one element on the basis of the starting point and of the encrypting byte Y. In one embodiment of the invention, an XOR operation with the historical byte of the previous encrypted byte is performed for the determined value of the historical byte. At first, e.g. a predefined random constant can be used as the previous value for the first byte to be encrypted (or for the first entity to be encrypted). For the next determined values, a predefined operation is performed between the result of the XOR operation formed between the elements of the encryption tables, the historical byte and the data byte to be encrypted. This can be e.g. an XOR operation and, that being the case, an XOR operation can be formed between the result of the XOR operation formed between the elements of the encryption tables, the historical byte and the data byte to be encrypted. This can be implemented e.g. as follows: 'result of XOR operation formed between the elements of the encryption tables' 0 'historical byte' 0 'data byte to be encrypted'. The determined result is an encrypted byte, which can be sent along an untrusted messaging channel or recorded encrypted. There can be a number of historical bytes and they can be calculated in different ways.

When encrypting the next byte of data intended for encryption, the next point from the starting point is used. The index of each encryption table can e.g. be increased by one, and if the index goes over the top limit of the encryption table, it can be continued from the start of the encryption table in question. Since the encryption tables are of different lengths and the lengths have no common factor, it is possible in this way, when encrypting the next byte, to move forward by the amount of the product of the lengths of the encryption tables without the same combination of indexes of the tables of the encryption tables being used again. A sequence is obtained with the method described above, the length of which sequence is the product of the lengths of the tables. During a sequence, each time there is a new encrypting byte with which the byte to be encrypted can be encrypted. The algorithm according to the invention can therefore be used to encrypt a message having a length of at most the length of the sequence.

Described below by means of exemplary equations is an example according to the invention, wherein CB (crypted byte) is an encrypted byte, Y is an encrypting byte generated by an algorithm, H is a historical byte and D is the plaintext data byte intended for encryption. In the examples, an XOR operation (bitwise exclusive or) is used, but instead of XOR, if so desired, a corresponding combination can be used with which the encryption can be conversely opened and which retains the even distribution of random numbers. The algorithm functions by encrypting one byte, or a byte pattern of predefined length, at a time.

The encrypted byte in sequence n can thus be formed as follows:

CB_n = Yn Θ H_n Θ D_n

If Y_n is a one-time random key, and a historical byte is not used, then the encryption is known as a onetime pad, which is known to be unbreakable. In this encryption algorithm, Y_n is formed by calculating from a plurality of random numbers in such a way that the same sequence is repeated so seldom that the length of the message to be encrypted is shorter than the sequence generated by the algorithm.

Decryption of an encrypted message can be performed e.g. in the following manner when the encrypting byte Y_n and the historical byte H_n are generated by means of an encryption key in the same manner as at the sending/encrypting end :

D_n = Yn θ Hn 0 CB_n The algorithm for Y can be formed in the following manner, where |x| means the length of table x and the values of the elements of an encryption table are random bytes, e.g. 0-255 in value, or with a sign digit e.g. -127 - 128, and where the index n means how many bytes are being encrypted :

Y_n= fy(n, A, B, C, D, E, F)

The value of the function fy depends on the number n and on all the encryption tables. The value of the function must use different combinations of the values of the tables in such a way that a large amount of results that are independent of each other are obtained. The function can be, for example:

Y_n = fy(n, A, B, C, D, E, F)

= A[n mod |A| ] 0 B[n mod | B| ] 0 C[n mod | C| ]

D[n mod | D| ] 0 E[n mod | E | ] 0 F[n mod | F| ]

In the solution of the invention, the sequence of XOR operations has no significance. In the examples above, the modulo operation used is a remainder from division, and the indexes of the encryption tables start from zero.

The index -1 of the historical byte to be used in conjunction with starting encryption can be a given random constant, which can vary for different keys. A historical byte can be determined e.g. as follows: H_n = YH_n 0 Hn-1 ,

where

YH_n=A[(n + Yn) mod |A| ]

An XOR operation is formed between the YH byte and the previous historical byte, and the result of this operation is recorded as a new historical byte. When encrypting the next byte, the recorded historical byte is used in the manner presented above and a new historical byte is formed and recorded. The historical byte does not need to be one byte. The encryption can also be used completely without a historical byte. The length of a historical byte can be any length whatsoever from one bit upwards; what is also essential is that it is calculated using the previous values of the historical byte.

There can also be more than one historical byte. If more than one historical byte is used, they can be calculated in different ways and/or from different tables.

According to one embodiment of the invention, the algorithm can, for example, be such :

Yn = A[n mod |A] 0 B[n mod | B| ] 0 C[n mod | C| ] 0 D[n mod | D | ] 0 E[n mod | E| ] 0 F[n mod | F| ], and

H_n= D[(n + Yn) mod | D | ] 0 H_n-i

Instead of a modulo operation, e.g. the indexes of the encryption tables can be used, the indexes being increased, or pointers which are increased in a predefined manner. In such a case, the embodiment can be further speeded up by giving the sum n + Y_n in the calculation of the historical byte to move over the limits of the encryption table into the next encryption tables (the encryption tables of the encryption key can be located to follow each in unbroken memory space) without a slow calculation of a division remainder or checking whether the top limit has been passed.

If it is desired to use the encryption method according to the invention for a number of different, possibly simultaneous, messaging events (e.g. multiple sockets), then the next key to be used can be agreed at the start of the session. In one embodiment of the invention, it can also be agreed that only a part of the key changes each time.

The sequence of the algorithm, i.e. the length after which it produces the same values for the encrypting byte Y_n, depends on the number of tables used and the lengths of said tables. If it is desired to break the algorithm by trying different alternatives as the values of the tables, the number of attempts needed depends on the cumulative length of the encryption tables (how many random numbers are in the encryption key) and on the lengths of the encryption tables. The encryption method according to the invention can also be used with rather small tables, in which case breaking the encryption trying all possible combinations is already difficult but the sequence is short. A longer sequence can be arranged in other ways, e.g. by forming an XOR operation between the encrypting byte generated with the algorithm according to the invention and the byte produced by some pseudorandom number generator (which produces a long sequence).

By changing the number and lengths of the tables to be used in the solution according to the invention, both the number of combinations and the length of the sequence that are needed to break the algorithm can be freely increased or decreased. The more tables there are, the slower the runtime performance; the longer the tables are, the more memory is needed.

If the size (cumulative length of the tables) of the encryption key used in the solution according to the invention were approx. 5000 bytes, the length of the sequence would be (if the tables were roughly of the same length) in the magnitude of 10²⁸. In this case, encrypted data in the magnitude of 3 billion terabits a second could be sent for one thousand years. The scale of magnitude of the different combinations is 2.7 * 10¹³¹⁶⁴.

In the solution according to the invention, instead of encrypting an individual byte, also a certain predefined number of bytes can be encrypted, e.g. four bytes at a time. In such a case, the values of the elements of the encryption tables must be of corresponding lengths, i.e. in the aforementioned case, each must be four bytes in length. The solution according to the invention can be used also with public key systems that are based on two parties agreeing between themselves about a secret key with the public key method, and the actual traffic can then be encrypted with this secret key. If it is desired to use the solution according to the invention in a public key system, an algorithm according to the invention can be used for encrypting the actual traffic. With the public key method, the encryption key to be used is agreed according to the solution of the invention. The actual traffic is then securely encrypted. A weakness in current systems is both agreement about the key and also encrypting the actual traffic, and by means of the solution of the invention the latter weakness can be rectified.

The symmetrical encryption method according to the invention is well suited for use in intranet-type cases without a public key, if all the users are machines known beforehand and under sole control of the user, e.g . in VPN networks.

It is obvious to the person skilled in the art that the different embodiments of the invention are not limited solely to the examples described above, and that they may therefore be varied within the scope of the claims presented below. The characteristic features possibly presented in the description in conjunction with other characteristic features can also, if necessary, be used separately to each other.

Claims

1. Method for encrypting data with a device or with an apparatus, characterized in that encrypted data is formed from the plaintext content to be encrypted, a predefined amount of data in length at a time, by means of an encrypting bit or bit pattern (Y_n) to be formed for each individual bit or individual bit pattern,

wherein the encrypting bit or bit pattern (Y_n) of the plaintext bit or bit pattern (D_n) is formed by means of an encryption key (203, 204, 300, 400), which encryption key comprises at least two encryption table (A, B, C) to be used in the encryption, which encryption tables have a different number of elements (al...a7, bl...b5, cl...c3) to each other, which elements comprise randomly formed data,

wherein the plaintext bit or bit pattern ((D_n), the encrypting bit or bit pattern (Y_n) and the elements (al...a7, bl...b5, cl...c3) of the encryption table are of the same length as each other, e.g. one byte in length, and

wherein the encrypting bit or bit pattern (Y_n) is formed :

- by selecting one predefined element from each encryption table (A, B,C) to be used in encrypting on the basis of the sequence number (n) of the bit or bit pattern to be encrypted, and by performing an XOR operation between all these selected elements,

in which method the encrypted bit or bit pattern (CB_n) is formed by performing XOR operations between the plaintext bit or bit pattern (D_n) to be encrypted and the encrypting bit or bit pattern (Y_n) that is formed, and

after encrypting one bit or bit pattern, the next bit or bit pattern is encrypted by selecting the next plaintext bit or bit pattern (D_n+i) and by forming an encrypting bit or bit pattern (Y_n+i) on the basis of the next predefined elements of the encryption tables in such a way that the sequence being formed from the encrypting bit pattern (Y_n, Y_n+i,...) is repeated so seldom that the length of the message to be encrypted is shorter than the sequence, i.e. length, generated by the algorithm, after which the encryption produces the same values of the encrypting byte (Yn).

2. Method according to claim 1, characterized in that the next element of the encryption table is the next element of the encryption table by index and/or, in a case in which the current element is the last element of the encryption table, the next element of the encryption table is the first element of the encryption table.

3. Method according to claim 1, characterized in that the next element is the element, determined according to a certain rule, of the encryption table.

4. Method according to any whatsoever of the preceding claims, characterized in that, the encrypting bit or bit pattern (Y_n) is formed as follows:

Y_n= A[n mod |A| ] 0 B[n mod | B| ] 0 ... 0 N[n mod | N | ]], where: - A[n mod |A| ] is the element, intended for the bit or bit pattern

(n), of the first encryption table,

- B[n mod | B | ] is the element, intended for the bit or bit pattern (n), of the second encryption table, and

- N[n mod | N | ] is the element, intended for the bit or bit pattern (n), of the Nth encryption table.

5. Method according to any whatsoever of the preceding claims, characterized in that the lengths of the encryption tables (A, B, C) are of different lengths to each other in such a way that the largest common factor of the number of elements of any two encryption tables whatsoever is 1.

6. Method according to any whatsoever of the preceding claims, characterized in that the lengths of all the encryption tables (A, B, C) are different prime numbers to each other.

7. Method according to any whatsoever of the preceding claims, characterized in that an element (al...a7, bl...b5, cl...c3) of an encryption table of an encryption key is one or more randomly selected bits or bit patterns or one or more randomly selected bytes, wherein the lengths of the encrypting bit or bit pattern (Y_n), plaintext bit or bit pattern (D_n) and/or encrypted bit or bit pattern (CB_n) correspond to the length of the element (al...a7, bl...b5, cl...c3) of the encryption table.

8. Method according to any whatsoever of the preceding claims, characterized in that in the method a starting point is determined, i.e. each encryption table has its own starting element from which the encryption is started.

9. Method according to claim 8, characterized in that the starting point is a constant, e.g. the index 0 in each encryption table.

10. Method according to claim 8, characterized in that the starting point is specific to the key, e.g. each encryption table has its own randomly drawn point that is known to the sender and to the recipient.

11. Method according to any whatsoever of the preceding claims, characterized in that the encrypted data is formed from the plaintext content to be encrypted, a bit or bit pattern at a time, by means of a historical bit or historical bit pattern (H_n), in addition to an encrypting bit or bit pattern (Y_n) to be formed for each individual bit or individual bit pattern, in such a way that the encrypted bit or bit pattern (CB_n) is formed by performing an XOR operation between the plaintext bit or bit pattern (D_n), the determined encrypting bit or bit pattern (Y_n), and the historical bit or historical bit pattern (H_n).

12. Method according to claim 11, characterized in that the historical bit or historical bit pattern (H_n) is formed using at least the sequence number (n) of the plaintext bit or bit pattern.

13. Method according to either of claims 11 or 12, characterized in that the historical bit or historical bit pattern (H_n) is formed by selecting one predefined element from one predefined encryption table on the basis of the sequence number (n) of the bit or bit pattern to be encrypted and on the basis of the encrypting bit or bit pattern (Y_n).

14. Method according to any whatsoever of claims 11 - 13, characterized in that a historical bit or bit pattern (H_n) is formed by forming an XOR operation between the selected element of the encryption table and the historical bit or historical bit pattern (H_n-i) of the previous bit or bit pattern to be encrypted.

15. Method according to claim 14, characterized in that the first value (Hi) of the historical bit or historical bit pattern of the first bit or bit pattern in sequence to be encrypted is determined on the basis of the starting point and of a predefined, possibly key-specific, random constant.

16. Method as according to claim 13, characterized in that when forming a historical bit or historical bit pattern, instead of an encrypting bit or bit pattern (Y_n), one or more predefined elements can be selected from some encryption tables on the basis of the sequence number (n) of the bit or bit pattern to be encrypted, and by performing an XOR operation between all these selected elements.

17. Method according to any whatsoever of the preceding claims, characterized in that another operation that connects two bits or bit patterns can be used instead of an XOR operation in such a way that the sequence of the bits or bit patterns is of no significance, and the result of the operation between two random bits or bit patterns is also random.

18. Method according to any whatsoever of the preceding claims, characterized in that the encrypted data is sent from the sending device (201, 202) via a data network or telecommunications connection to the receiving device (201, 202).

19. Method according to claim 18, characterized in that the receiving device (201, 202) decrypts the encryption of the encrypted data received, a predefined amount of data in length at a time, by means of the encryption key.

20. Method according to claim 18 and 19, characterized in that the receiving device (201, 202) decrypts the data received, a predefined amount of data in length at a time, as follows:

D_n = Yn Θ H_n Θ CB_n, where - CB (crypted byte) is the encrypted bit or bit pattern that is n in sequence,

- Y_n is the bit or bit pattern generated from the encryption key of the algorithm,

- Hn is the historical bit or bit pattern or historical bit pattern of the bit or bit pattern n, and

- D_n is the plaintext bit or bit pattern received that is n in sequence.

21. Method according to any whatsoever of the preceding claims, characterized in that the encrypted data is recorded in the memory means of the device (201, 202), such as in mass memory.

22. Arrangement for encrypting data with a device or with an apparatus, characterized in that the arrangement comprises means arranged for the device (201, 202) for recording and managing an encryption key (203, 204, 300, 400), means for performing data encryption and for decrypting data encryption with an encryption key, and

wherein the arrangement is adapted to form encrypted data from the plaintext content to be encrypted, a predefined amount of data in length at a time, by means of an encrypting bit or bit pattern (Y_n) to be formed for each individual bit or individual bit pattern,

wherein the arrangement is adapted to form the encrypting bit or bit pattern (Y_n) of the plaintext bit or bit pattern D_n by means of an encryption key, which encryption key (203, 204, 300, 400) comprises at least two encryption table (A, B, C) to be used in the encryption, which encryption tables have a different number of elements (al...a7, bl...b5, cl...c3) to each other,

wherein the arrangement is adapted to form an encrypting bit or bit pattern (Y_n) by selecting one predefined element from each encryption table (A, B,C) to be used in encrypting on the basis of the sequence number (n) of the bit or bit pattern to be encrypted and by performing an XOR operation between all these selected elements, wherein the arrangement is adapted to form an encrypted bit or bit pattern (CB_n) by performing XOR operations between the plaintext bit or bit pattern (D_n) to be encrypted and the encrypting bit or bit pattern (Y_n) that is formed, and

after encrypting one bit or bit pattern, the arrangement is adapted to encrypt the next bit or bit pattern by selecting the next plaintext bit or bit pattern (D_n+i) and by forming an encrypting bit or bit pattern (Y_n+i) on the basis of the next predefined elements of the encryption tables in such a way that the sequence being formed from the encrypting bit pattern (Y_n, Y_n+i,...) is repeated so seldom that the length of the message to be encrypted is shorter than the sequence, i.e. length, generated by the algorithm, after which the encryption produces the same values of the encrypting byte (Y_n).

23. Arrangement according to claim 22, characterized in that the arrangement is adapted to implement any method whatsoever according claims 2 - 21.