ES2363355A1 - System for slowing down the transfer rate of a device by the cryptographic method - Google Patents

Abstract

The invention relates to a system for slowing down the transfer rate of a device by the cryptographic method, including: a processing means (1) configured to: select a type of encryption encrypt information according to the type of encryption selected, including: converting the information to be encrypted into a string of numeric characters, dividing the string of characters into blocks of a variable number of characters and encrypting each of the blocks according to the type of encryption selected and randomly generating a plurality of codes. The system additionally includes: a memory (2) that stores the plurality of codes generated, the encrypted information and the operations and intermediate variables created by the processing means and a means of input and output (3) configured to receive external information for carrying out the encryption tasks.

Description

Rate slowdown system transfer of a device by cryptographic method.

Field of the Invention

The present invention belongs to the field of cryptography.

State of the art

So far cryptography has been used in its proper sense, encrypt with a key and decrypt with a key.

The following documents are remarkable related to the present invention.

US2005210249-A1 offers an information storage device that is encryption to maintain content security and subsequent transmission of the same to other devices to be able to manipulate them only in case the authentication is correct and the data flow has been completely transferred. Do not However, once the access code is known, you have permission to use the data and manipulate them while allowing dissemination and offer them clearly to anyone else without prior encryption, violating copyright.

US7434067-B1 presents a comparator of security authorizations preventing indiscriminate access and allowing access under attributes personal The comparator has a back door that allows access to decryption and decryption itself. But comparator is not expressly referred to content and does not present a back door that allows access to clear data from absolute form

US2008226069-A1 presents the encryption of data obtained by input devices, like a keyboard or any other similar medium, being able to decrypt them through functions of a processing module. Do not However, it does not offer a quantification of the difficulty of deciphering or targeting high amounts of information from data. In document US2008226069-A1 are encrypted contents but it is possible to decipher them so that they can be manipulated and disseminated without control breaking the rights of authorship, aspect that should be controlled.

A system of slowing down the transfer rate of a device that allowed to exercise some control over the time required in decipher an information.

Description of the invention

The invention presents a system of slowing down the transfer rate of a device by cryptographic method based on decryption time control of the information. The method comprises the following stages:

1. Select the encryption to use

Choosing an encryption method to encrypt the Clear information. Encryption can be selected from encryption symmetrical DES, T-DES, AES, etc. and asymmetric RSA, EIGamal, Elliptic Curve, etc.

2. Encrypt the information

The slowdown will be set based on the security to be attributed to the encrypted document, to the greatest or less confidentiality that you want to attribute, and to the disposition or no immediate provision that you want to grant it. With To this end, the method applies a variable decryption difficulty that It will result in a variation of the time required in decryption. By their nature, symmetric ciphers will be faster than asymmetric

In the encryption stage, you first convert the information document into a character string numeric (binary, decimal, etc.). If the document is audio or video can be passed directly to a character string binary, if it is a text document, you can pass each character to its corresponding ASCII character, or use any other system conversion, and for example, pass the character string to a string of binary characters.

For encryption, the document is divided into k character blocks to encrypt each block according to encryption chosen in the previous stage. Once encrypted each of the These blocks together will form the encrypted text.

3. Generate a plurality of keys

This stage is what characterizes the proposed slower, in it, a plurality of keys is randomly generated. If the decryption key is k j, the method would randomly generate a plurality of keys that together with k j, would be delivered to the recipient. Thus the delivery will consist of { k 1, k 2, ... k j, ... k s-1, k s. The number of keys offered will mean that - when "s" tends to infinity - the recipient has to prove approximately half of the number of keys delivered to decipher the document. Therefore, to increase the decryption time a thousand times, the method must randomly construct a plurality of two thousand keys.

Therefore, the rate slowing method of transferring a device by cryptographic method understands:

?

select a type of encryption;

?

encrypt information by type of selected encryption, including: convert the information to Encrypt in a string of numeric characters, divide the string from block characters of a variable number of characters and encrypt each of the blocks according to the type of encryption selected in the previous stage;

?

randomly generate a plurality of keys;

?

distribute a key set to each recipient, each set consisting of a variable number of keys comprising the decryption key.

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Preferably, the selection of a type of Encryption will comprise the alternative selection between:

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symmetric encryption, comprising: DES, T-DES, AES;

?

asymmetric encryption, comprising: RSA, EIGamal, Elliptic Curve.

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The device that implements the previous method understands:

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a means of processing configured to:

-

select a type of encryption;

-

code information according to the type of encryption selected, comprising: convert the information to be encrypted into a character string numeric, divide the character string into blocks of a number character variable and encrypt each of the blocks according to the type of encryption selected;

-

randomly generate a plurality of keys;

?

a memory that stores the plurality of generated keys, encrypted information and operations and intermediate variables carried out by the means of processing

?

means of entry and exit configured to receive and send information from abroad to Perform encryption tasks.

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Preferably, the processing means alternately select the type of encryption between:

?

symmetric encryption, comprising: DES, T-DES, AES;

?

asymmetric encryption, comprising: RSA, EIGamal, Elliptic Curve.

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Because the submission to a different processor turns different the decryption speed is done it is necessary that the device has a known processor embedded based on which decryption is done. This allows to control the time for offering internal information, since time decryption is given by the capacity of the processor.

Because the encrypted document could have a greater or lesser need to be slowed down is applied on it the previous method. When the decryption key is unknown, the only usual way to get the text clear is to try a by one all the possible keys. This usually takes so long. which makes this option unfeasible. Therefore, stand at the point intermediate between brute force (try all possible keys) and knowledge of the key (try a single key), allows slow down decryption as a set of keys is offered Among which is the correct one. The more keys offered, The harder it will be to solve the decryption.

Brief description of the drawings

Then, to facilitate the understanding of the invention, by way of illustration but not limitation, will be described an embodiment of the invention that refers to a figure.

Figure 1 represents the device of slow down data transfer rate by encryption.

Detailed description of one embodiment

An embodiment is detailed below. of the system that is intended to be patented.

1. Select the encryption to use RSA encryption

RSA encryption is the encryption method that is will use in the preferred embodiment of the invention. The Algorithm RSA, proposed in 1978 owes its name to the initials of the last names of its inventors Ron Rivest, Adi Shamir and Leonard Adleman, is based on the computational difficulty of obtaining the prime factors of very high numbers. It's easy to look for cousins elevated and then multiply them to create a larger number, but starting from a large number and looking for its prime factors is a extremely complex operation.

Initial specifications

To make use of this Algorithm they must Define a series of structures. The following table indicates the steps to be taken and the way in which the elements involved in them, such elements may be Secrets or no secrets. The secret elements should not be given to to know, while the non-secrets will be public and must Offer to whomever requests or specifies.

one

Step 3 is easily deductible from the definition of Euler's function given the generation of "r" as a product of two cousins.

The general formula of this function is:

2

where p 1, p 2, p 3, ..., p n are the prime factors of "r".

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This Euler phi function on "n", also called the Euler Indicator, it results in the number of relative cousins who have "n" less than himself. So, for example, \ varphi (20) = 8, since 20 decomposes into two prime factors, 2 and 5, the first raised to 2, and the second raised to unity. They are therefore the following relative cousins with 20 minors than himself: 1, 3, 7, 9, 11, 13, 17, 19.

Public and private keys present a Strong relationship between them. To get this relationship between SK and PK becomes an extension of Euler's Theorem:

If a \ equiv b mod r , this means that for every exponent "m", a ^ {m} \ equiv b ^ m mod r . This leads to Euler's formula, a ^ {\ phi (r)} \ equiv 1 mod r can be rewritten as:

3

where "a" is relative cousin with "r".

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Also, as a \ equiv b mod r , then a \ times c \ equiv b \ times c mod r , for every element "c" belonging to the integers.

Using both results you can infer:

4

where the plain text X (plaintext) is a relative cousin with "r" -a restriction that follows it will indicate how remove-.

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The relationship between public and private keys, PK, SK, is as follows.

They must fulfill the relationship SK \ times PK = m \ times \ phi ( r ) +1, which can be expressed as follows:

fifty

Being able to express the previous relationship as:

5

Encryption and decryption

Noting for the usual English capital letters of encipherment and decipherment, "E" and "D" respectively, and offering in the subscripts the key to use, it can be expressed as Compact way encryption and decryption of RSA Algorithm how:

6

How are these encryption and decryption operations they are commutative, -the reason is that SK * PK = PK * SK- it follows that Encrypting decrypted text is the same as decrypting encrypted text:

7

Improving the Algorithm

There are a number of aspects to follow considering, because what looked like a simple Algorithm, It contains a series of deep and complex aspects that cannot be ignored, so that they will be contemplated continuation.

It is known that X PK mod r = ( X + m \ times r ) PK mod r for any integer "m", and any plain text X, resulting in X, X + r, X + 2r, X + 576r, ... offer the same encrypted text. That is, the function is a function such that many elements - infinites - of the initial set offer the same image in the final set. To restrict these possibilities to a one-to-one function, the text X must be restricted to the set {0, 1, 2, .... r-1}. This entails the application, as previously expressed, of the formulas for encryption and decryption in a bijective manner, one on one.

It has been proven that the realization of a series of guidelines, in the use of the RSA Algorithm, it makes it difficult to break, In addition to training it to work properly.

a) The choice of prime numbers

They have to select two prime numbers, "p" and "q", different each. The product r = p * q is made public, but both numbers cousins must remain secret, or their traces removed, that is, that they are unknown to anyone, including the cipher part.

The inventors of the Algorithm recommend as additional protection a series of additional choices:

one.

"p" and "q" must differ in a few digits, but without being too close.

2.

So much (p-1) as (q-1) must contain large prime factors, p 'and q', respectively.

3.

He mcd [(p-1), (q-1)] has to be small.

Four.

Than (p'-1) and (q'-1) have factors big cousins, p '' and q '' respectively.

b) The choice of keys

It must be fulfilled that SK \ times PK \ equiv 1 mod \ phi ( r ), that is, that the product of the private and public key is relative relative to Euler's phi function. It must also be easy to compute SK and PK. Below is how to meet these requirements.

Let d = mcd (a, n), the greatest common factor of two numbers "a" and "n". The congruence aX \ equiv b mod n can be resolved, that is, an entire "X" can be found that satisfies it only if the gcf (a, n) divides "b". Without entering into the proof of this theorem, what is intended is that the gcf (a, n) divide a b. If that gcf (a, n) = 1, it always happens that 1 will divide b. Then we will find that lcd (a, n) is 1.

If the two equations d = mcd (a, n) and aX \ equiv b mod n are made, they are actually 1 = mcd (SK, \ phi (r)) and SK \ times PK \ equiv 1 mod \ phi ( r ). To achieve what is sought, which is that the congruence SK \ times PK \ equiv 1 mod \ phi ( r ) can be resolved, it is simply to look for reality that 1 = mcd (SK, \ phi ( r )).

The gcf (SK, \ phi ( r )) = 1 when SK and \ phi ( r ) have no common factors, that is, they are relative cousins between them.

Making use of Euclidean algorithm is possible to find a suitable method for know relative cousins of a given number, being able to find starting from SK the value of PK, and vice versa, which would complete the private (SK) and public key search algorithm (PK)

2. Encrypt the documentation

To encrypt a message it must be divided previously in blocks such that they do not exceed the value r-1. Otherwise, functions would be obtained ambiguous by allowing diverse representations. a way to encoding a literary text is transforming each letter to a code Numeric, ASCII, ANSI, or any other. Assuming A = 01, B = 02, ... Z = 27 (including the letter Ñ as proper to the study alphabet). In addition, values could be assigned to other different signs and perhaps necessary as,) (¿! @ /;.-_ {} ç + * \ simz \ ccirculo ... so You should look for an appropriate assignment between each sign and a number. However, as an example this coding will be maintained, for simplicity

If the message is "In a spot of La Mancha, of whose name I don't want to remember ", after putting it in capital letters and remove the tildes and blanks and commas, could write as:

[051422141222070119040512011301140308010405032226161416130219051416182209051916010316190401
191305].

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The Algorithm values are now chosen. For example, p = 100003 and q = 1200007. The result of r = p * q =
120004300021.

The text to be encrypted is divided so that it does not exceed the value r-1, that is, 120004300020. To to comply with this specification the text will be divided into following 8-digit blocks:

[05142214, 12220701, 19040512, 01130114, 03080104, 05032226, 16141613, 02190514, 16182209, 05191601, 03161904, 01191305].

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Assuming that SK is 60238691159. To calculate PK, it has to be satisfied

80

getting a value of PK = 671627.

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Then all the elements are encrypted of the plain text, raising each of them to the PK power and calculating the module value r.

This gives us the following values:

8

\hskip0,1cm

74143246285,

\hskip0,1cm

117149080760,

\hskip0,1cm

78437239131,

\hskip0,1cm

20569639272], lo que configura el texto cifrado.[83071342073, 11341992260, 92701932291, 33584471135, 80369499959, 24635225570, 45048183052,
48263380423,

 \ hskip0,1cm 

74143246285,

 \ hskip0,1cm 

117149080760,

 \ hskip0,1cm 

78437239131,

 \ hskip0,1cm 

20569639272], which sets the encrypted text.

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The decryption process consists of taking each one of the encrypted blocks, and raise them to SK for later get your modular result on r.

9

Applying these operations you get the values:

[05142214, 12220701, 19040512, 01130114, 03080104, 05032226, 16141613, 02190514, 16182209, 05191601, 03161904, 01191305].

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If you then put each of the pairs of digits in literal value, according to the pattern A = 01, B = 02, ... Z = 27, you get the text -after inserting the original blanks-: "In a place in La Mancha, whose name I don't want remember me. "

However, in this phase only the message, not doing the decrypted phase. Only the text is built encryption:

\hskip0,1cm

74143246285,

\hskip0,1cm

117149080760,

\hskip0,1cm

78437239131,

\hskip0,1cm

20569639272].[83071342073, 11341992260, 92701932291, 33584471135, 80369499959, 24635225570, 45048183052,
48263380423,

 \ hskip0,1cm 

74143246285,

 \ hskip0,1cm 

117149080760,

 \ hskip0,1cm 

78437239131,

 \ hskip0,1cm 

20569639272].

3. Generate a plurality of keys: Breaking the brute force algorithm

Try to break the RSA encryption algorithm by brute force means that the encrypted text is divided,

\hskip0,1cm

74143246285,

\hskip0,1cm

117149080760,

\hskip0,1cm

78437239131,

\hskip0,1cm

20569639272].[83071342073, 11341992260, 92701932291, 33584471135, 80369499959, 24635225570, 45048183052,
48263380423,

 \ hskip0,1cm 

74143246285,

 \ hskip0,1cm 

117149080760,

 \ hskip0,1cm 

78437239131,

 \ hskip0,1cm 

20569639272].

and you try to recover the original text in Of course knowing only what is public, which is the value of r and PK. As SK is unknown, all j numbers from 1 must be tested until r until finding the value that taking any fragment of encrypted text, and raised to that value j module r give a number that put in letters offer a coherent sentence in a language. Due to the huge amount of values at stake, the precise time To perform this operation it is impossible to contemplate. This is a brute force attack.

Slow Deciphering

The method proposed here is halfway between brute force and knowledge of the SK key. In this case the user is given a set of keys, randomly generated including the correct one, for example the set: {1947284219, 60238691159, 817327811}. The choice of deck extension keys or keys will give the average time to obtain the text in Of course, the text decryption is controlled.

For each of these SKj values, the results obtained on the first and second block of the text Encryption are as follows: 83071342073 and 11341992260.

For 1947284219, you get: [39588400026, 118687772076]. It can't be because the first letter doesn't exist, "39" is out of the alphabet.

For 60238691159, you get: [05142214,12220701]: ENUNLUGA.

For 817327811, you get: [68908968738,18311139167]: It can't be because the first letter doesn't exists, "68" is out of the alphabet.

With this bunch of keys it is clear that the SK it's 60238691159, since you always get letters, and with a certain semantic sense, so this SK key would be applied especially Encrypted text to get all full text clear.

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The end result is that it has taken three times more to decipher the text than if only One key, the correct one. In general, what is usually given is a larger number of keys, for example 10,000, which makes half the correct key is around half, around the 5,000, hence when 5,000 have been tested, it may have been Given the correct one.

The possibility of this retarder lies in assume for example a file where several documents are placed text, or audio, or video, and each of them with certain major or minor confidentiality, which will mean decryption It will be slower or faster. So if for example, if they had 3 documents, one of very confidential value, another of medium and another of low, a slowdown rate would apply for each document, for example of 10,000 keys for the most confidential, of 3,000 keys for the medium, and 100 keys for the minor confidentiality This would mean that the most sensitive documentation it would be the most difficult to handle and dispose of, being the least important in terms of security the easiest is going to be deciphered

Thus, if the document consisting of encrypting and slowing down was the first chapter of a book, specifically "El Quijote", which begins with "En un un de la Mancha ...", and ends in "came to call it Dulcinea del Toboso, because he was a native of Toboso, named in his opinion a musician and pilgrim and significant, like everyone else he and his things had put ", has a total of 8202 characters. If they are divided into 4-letter blocks, 2051 blocks will be obtained, the last of which will only have two letters. Applying normal encryption, the time it takes for this execution to be decrypted assumes an Intel (R) Core (TM) 2 CPU T5600 @ 1.83 Ghz of 2,112.52 seconds, that is, about 35 minutes. If it were desired that the process lasted longer, a greater number of keys would be offered. If the number of keys that were given outside of {61627611, 99299112, 76764913, 8723618246, 7624551234, 89746841634, 72364273, 8237481273, 3248846423, 34234234, 234235454, 12098984823, 34245, 342412412, 464246456, 4624244356
878768769, 989775565, 891818913, 83578774734, 4878742374723, 3434134, 87873858179, 3478783478,
4387865324, 31573894783, 348946324, 12347893784, 234782844, 347878341, 34783743343, 24134512532,
3423424234, 341353515, 1356436, 6564564345, 3454324234, 234242412, 43534534534, 4543453, 7687967657, 1947284219, 938758234, 20930353, 1029333911, 198001001, 8989781172, 60238691159, 60238691159
6651829934}, and each of them will be tested in this order, upon reaching the 49th the decryption would be resolved, which means a time of 108497.34 on our device, that is, a little more than 30 hours to be able to have the first chapter of the novel "Don Quixote".

The way to apply the system industrially described follows from the description itself. Do not However, its applicability in the industry related to computer security services, financial, governmental, police and, in general in the industry related to all those areas or services that require the blocking of information that is available from indiscriminate way. It's about making the availability of the information is controlled in time, and if it already was, that no is available until the decryption time has expired, a time that is previously controlled.

This control of time and resources in the availability of information make it useful in processes of information engineering, control and data safeguard or data protection, as in the rights From author. For example, the manipulation of information by from third parties could be so expensive in time and resources for them that made its availability unfeasible, but it was more easy, light and less expensive by the authorized holder, who It would have a smaller set of keys.

Once the invention has been clearly described, notes that the particular realizations above described are subject to modifications of detail provided that do not alter the fundamental principle and the essence of the invention.

Claims (4)

1. Rate slowdown method transfer of a device by cryptographic method that It comprises the stages:

?

select a type of encryption;

?

encrypt information by type of selected encryption, including: convert the information to Encrypt in a string of numeric characters, divide the string from block characters of a variable number of characters and encrypt each of the blocks according to the type of encryption selected in the previous stage;

characterized in that it additionally comprises the stages:

?

randomly generate a plurality of keys;

?

distribute a key set to each recipient, each set consisting of a variable number of keys comprising the decryption key.

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2. Method of slowing down the transfer rate of a device by cryptographic method, according to the preceding claim, characterized in that the selection of an encryption type comprises the alternative selection between:

?

symmetric encryption, comprising: DES, T-DES, AES;

?

asymmetric encryption, comprising: RSA, EIGamal, Elliptic Curve.

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3. System of slowing down the transfer rate of a device by cryptographic method characterized in that it comprises:

?

processing means (1) configured to:

-

select a type of encryption;

-

code information according to the type of encryption selected, comprising: convert the information to be encrypted into a character string numeric, divide the character string into blocks of a number character variable and encrypt each of the blocks according to the type of encryption selected;

-

randomly generate a plurality of keys;

?

a memory (2) that stores the plurality of generated keys, encrypted information and operations and intermediate variables carried out by the means of processing

?

means of entry and exit (3) configured to receive and send information from abroad to Perform encryption tasks.

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4. System for slowing down the transfer rate of a device by cryptographic method, according to claim 3, characterized in that the processing means (1) alternately select the type of encryption from:

?

symmetric encryption, comprising: DES, T-DES, AES;

?

asymmetric encryption, comprising: RSA, EIGamal, Elliptic Curve.