SYSTEM AND METHOD FOR QUANTUM-SAFE AUTHENTICATION, ENCRYPTION AND DECRYPTION OF INFORMATION
20230224148 · 2023-07-13
Inventors
- Olivier Francois Roussy NEWTON (Vancouver, CA)
- Andrew DEONARINE (Angus, CA)
- Nicolas Alexandre Roussy NEWTON (Vancouver, CA)
- Railton FRITH (Little Kimble, GB)
Cpc classification
H04L9/0858
ELECTRICITY
H04L9/0819
ELECTRICITY
International classification
Abstract
Aspects and embodiments of the present invention relate to a method and system for generating a private cryptographic key for use in a secure cryptogram for transmission between a first entity and a second entity. The method may comprise: selecting a random vector defined in an n-dimensional vector space shared between the first entity and the second entity, the vector comprising one or more component coordinates defined in the n-dimensional vector space, each component coordinate being associated with one or more bits; determining the one or more bits associated with each component coordinate comprised in the random vector; and generating the private key in dependence on the one or more bits associated with each component coordinate comprised in the random vector.
Claims
1-63. (canceled)
64. A method of generating a private cryptographic key for use in a secure cryptogram for transmission between a first entity and a second entity, the method comprising: generating an n-dimensional vector space shared between the first entity and the second entity prior to selecting a random vector in the n-dimensional vector space, comprising the steps of: generating a random binary string; dividing the random binary string into a plurality of discrete sub-sections, each sub-section comprising a plurality of bits; associating an index to each sub-section; projecting the binary string into the n-dimensional vector space using a projection function, the projection function mapping the indices associated with at least some of the subsections, to different coordinate values in the n-dimensional vector space; selecting the random vector defined in the n-dimensional vector space shared between the first entity and the second entity, comprising generating a random sequence of indices and selecting the random vector by identifying the coordinate value associated with each index in the sequence of randomly generated indices, each coordinate value being associated with a plurality of bits; determining the plurality of bits associated with each coordinate value comprised in the random vector, by identifying the index associated with each coordinate value, and determining the plurality of bits associated with each coordinate value in dependence on the identified index; and generating the private key in dependence on the plurality of bits associated with each coordinate value comprised in the random vector.
65. The method of claim 64, comprising: transmitting information associated with the random vector to the second entity, the information associated with the random vector enabling the second entity to recover the private key from the shared n-dimensional vector space.
66. The method of claim 65, wherein the information associated with the random vector comprises information indicative of the one or more coordinate values associated with the random vector.
67. The method of claim 65, comprising: generating the cryptogram in dependence on the private key; and transmitting the cryptogram to the second entity, the cryptogram comprising confidential information recoverable by the second entity in dependence on the recovered private key.
68. The method of claim 67, comprising: compressing the confidential information with a lossless compression algorithm; combining the compressed confidential information with random data; generating the cryptogram by encrypting the compressed confidential information combined with the random data; wherein the cryptogram comprises information enabling the confidential information to be distinguished from the random data; and optionally compressing the random data with a lossy compression algorithm; and generating the cryptogram by encrypting the compressed confidential information combined with the compressed random data.
69. The method of claim 67, comprising the steps of: generating a first nonce; encrypting the first nonce using the generated private key; forwarding the encrypted first nonce from the first entity to the second entity; receiving a response message from the second entity comprising a second nonce; determining if the first nonce and the second nonce are correlated; authenticating the second entity in dependence on the first nonce and the second nonce being correlated; and optionally comprising the steps of: generating a third nonce; encrypting the third nonce using the generated private key; forwarding the encrypted third nonce from the second entity to the first entity; receiving a response message from the first entity comprising a fourth nonce; determining if the third nonce and the fourth nonce are correlated; and authenticating the first entity in dependence on the third nonce and the fourth nonce being correlated.
70. The method of claim 64, comprising: generating the random vector using a mathematical function, the mathematical function comprising a pseudo-random number generator configured to generate random coordinate values defining the random vector; and optionally generating the random vector using a mathematical function comprising a pseudo-random number generator seeded with a value from a source of random numbers.
71. The method of claim 64, comprising: generating the random vector using a quantum key distribution protocol executed between the first and second entities, the quantum key distribution protocol being configured to generate the random sequence of indices, and associating the random sequence of indices with coordinate values defining the random vector.
72. The method of claim 64, wherein the binary string comprises a linear array of bits, and the projection function is configured to map the linear array of bits to an n-dimensional array of bits comprised in the n-dimensional vector space.
73. The method of claim 64, wherein the n-dimensional vector space comprises any one of: i. one or more fractal dimensions; and ii. one or more nested complex dimensions.
74. The method of claim 64, wherein the projection function is a state-dependent one-way function.
75. The method of claim 64, wherein the step of generating the random binary string comprises: the first entity generating a first random binary string; the second entity generating a second random binary string; and combining portions of the first and second binary strings to generate the binary string.
76. The method of claim 75, wherein the portions of the first and second binary strings are randomly combined.
77. The method of claim 75, wherein the portions of the first and second binary strings are combined in accordance with one or more of: i. a mixing function; ii. a merging function; iii. a substitute function; iv. an exchange function; v. a shuffle function; and vi. a riffle shuffle function.
78. The method of claim 75, comprising combining portions of the first and second binary strings using an exclusive OR operator “XOR”.
79. The method of claim 64, comprising: generating the shared n-dimensional vector space in a secure environment.
80. The method of claim 64, comprising: generating the random sequence of indices using a random number generator.
81. The method of claim 64 comprising: partitioning the random binary string into two or more separate partitions; and projecting at least a portion of the separate partitions into the n-dimensional vector space using the projection function.
82. The method of claim 81, comprising: partitioning the random binary string into a plurality of partitions of equal length; or partitioning the random binary string into a random number of partitions, each partition having a random length.
83. The method of claim 64, comprising: generating the private key by combining the plurality of bits associated with each component coordinate comprised in the random vector; and optionally generating the private key by combining the plurality of bits associated with adjacent component coordinates comprised in the random vector.
84. The method of claim 83, wherein the plurality of bits associated with each component coordinate comprised in the random vector are combined in accordance with a logical operator; and optionally wherein the logical operator is an exclusive OR operator “XOR”.
85. The method of claim 64, wherein the private key is a one-time key, and the method comprises: generating a new private key for each new cryptogram required for transmission between the first entity and the second entity.
86. A system for generating a private cryptographic key for use in a secure cryptogram for transmission between a first device and a second device, the system comprising a processor and a random number generator, the random number generator configured to generate a random binary string and a random sequence of indices, and wherein the processor is configured to: generate an n-dimensional vector space shared between the first device and the second device, comprising the steps of: dividing the random binary string generated by the random number generator into a plurality of discrete sub-sections, each sub-section comprising a plurality of bits; associating an index to each sub-section; projecting the binary string into the n-dimensional vector space using a projection function, the projection function mapping the indices associated with at least some of the subsections, to different coordinate values in the n-dimensional vector space; selecting a random vector defined in the n-dimensional vector space shared between the first device and the second device, by identifying the coordinate value associated with each index comprised in the random sequence of indices generated by the random number generator, each coordinate value being associated with a plurality of bits; determining the plurality of bits associated with each coordinate value comprised in the random vector, by identifying the index with each coordinate value, and determining the plurality of bits associated with each coordinate value in dependence on the identified index; and generating the private key in dependence on the plurality of bits associated with each coordinate value comprised in the random vector.
Description
BRIEF DESCRIPTION OF DRAWINGS
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DETAILED DESCRIPTION OF THE INVENTION
[0122] A detailed description of one or more embodiments of the present invention is provided below along with accompanying figures that illustrate the principles of the invention. This detailed description and accompanying figures illustrate the present invention by way of illustrative example only, and is not to be construed as limiting. Alternative embodiments are envisaged that are not explicitly described herein, but which adopt the operative principles of the embodiments described herein, and which would be obvious to the person skilled in the art on the basis of the presently provided illustrative examples. The description will clearly enable one skilled in the art to make and use the invention, and describes several embodiments, adaptations, variations and alternatives and uses of the invention, including what is presently believed to be the best mode and preferred embodiment for carrying out the invention. It is to be understood that routine variations and adaptations can be made to the invention as described, and such variations and adaptations squarely fall within the spirit and scope of the invention. For the purpose of clarity, technical material that is known in the technical fields related to the invention has not been described in detail so that the invention is not unnecessarily obscured. Such details relate typically to background information widely known in the field of cryptography, and which would form part of the general background knowledge of the person skilled in the art.
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[0129] If the devices do not pass security checks, contain low quality random data or fail to authenticate, then a stream random noise is produced, rather than eOTP data. In the case of an unauthorized individual attempting to perform cryptanalysis by creating a predictable pattern to enable later decryption, random noise, generated by each devices' RNG [660], makes it difficult for hackers to determine if eOTP data is being transmitted or not or even if the random data should be used at all. The random noise is not mixed/merged/entangled with any other device's so at a later stage the unauthorized individual's device(s) will be excluded and unable to decrypt the other devices cipher text. After the eOTP is created, the devices can then be separated and their data is now securely encrypted. Creating the eOTP is a one-time process and will not be repeated until reset to manufacturers default settings. When only a fraction of the OTP capacity is entangled, the remaining capacity maybe be used and this process repeated with another possibly different group of devices. For additional security measure, resetting the device without a partner, by being self-partnered destroys the contents of all local OTPs within the device and across hardware software embodiments writes new random information into the OTPs rendering the device unable to decrypt any of the previous encrypted ciphertext such that it cannot participate in encryption, or be linked to any recorded or previous encryptions.
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[0134] Each index into a dimension consists of a linear vector that can access/index stored data from a data partition (or multiple data partitions) in the ppOTP. Next, information from the ppOTP is then accessed using the linear vectors of memory that comprise coordinates in the complex space. For example, the ppOTP is partitioned into 4 partitions and projected into a 4-dimensional complex space. In software terms, this is the equivalent of taking a single dimensional array a[x . . . n] and splitting it into four preferably non-overlapping parts, p.sub.1[x.sub.1 . . . n.sub.1], p.sub.2[x.sub.2 . . . n.sub.2], p.sub.3[x.sub.3 . . . n.sub.3] and p.sub.4[x.sub.4 . . . n.sub.4]. Then, each element in each partition is stored/referenced in the linear arrays which comprise the dimensions of the complex space (in this example, a 4-dimensional complex space with dimensions d.sub.2, d.sub.2, d.sub.3, and d.sub.4). When the ppOTP data is accessed through the complex space, a path (vector of coordinates) is provided through each of the multiple dimensions. The index coordinates are initially determined using nonce from the RNG [1050], and each path vector may have a fixed or random number of coordinates, indicating positions in the various dimensions. Using this path vector, a set of values can then be calculated from the complex space projected ppOTP, this process being referred to as a vector set calculation [1060]. In this process, data is retrieved from each coordinate specified in the path vector, and then mixed (preferably XORed) with the next piece of data in that path vector at the next coordinate. This walk process is repeated until a final set of values E.sub.1, E.sub.2, etc. are calculated for a corresponding set of vectors, which completes the virtualization into the complex space. Since each vector in the vector path corresponds to a unit of data in the original pOTP (which in turn corresponds to a unit of data in the original plaintext/other data), the resulting values E.sub.1, E.sub.2, . . . E.sub.n can be mixed and then be XORed (or using some other reversible commutative operator) with the original plaintext/other data x.sub.1, x.sub.2, . . . x.sub.n to produce cipher data c.sub.1, c.sub.2, . . . c.sub.n [1070]. Each vector v.sub.n in a vector set s can be created by moving between a given set of dimensions (d.sub.1 . . . d.sub.n) in a random order, using random coordinates in each of those dimensions (without a collision by reusing the coordinates in a particular dimension). Vectors can be of different lengths, reusing a dimension, but preferably not the same coordinate in that dimension. If, when creating the next coordinate in a vector set, there is an attempt to iterate to the next dimension but that exceeds the largest dimension d.sub.n, then one could move to the first dimension in the space (e.g. d.sub.1), or to a random dimension (and use a random coordinate in this dimension that has not been used before).
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[0136] Once random data has been generated by or loaded from the RNG source (which may consist of random integer or floating point numbers, which are calculated in firmware/software by calling the appropriate opcode, which in turn generates random bits), the first version of the OTP, the physical OTP (pOTP) is created [1150] by using the random numbers from the RNG to generate random bits. For convenience, the random bits may be organized into units of bits corresponding to the units of information in the original plaintext/other data that is to be encrypted or decrypted. For instance, if the original plaintext was stored in 32-bit units (words), then the pOTP bits would be stored in 32-bit words as well.
[0137] In each workflow, starting OTP data [1150], which normally consists of a pOTP, is processed using a different operation, such as partitioning, entanglement, virtualization (accessing using complex space virtualization), or another operation(s). Workflows can have different numbers of steps depending on the number of operations performed. These operators could be performed in different sequences and can be skipped and/or repeated. An optional error-checking step [1155] (using randomness extraction/NIST/other standards) is performed on the output from the first operation. This produces different output depending on the workflow, and is considered step 1 [1160]. Then, another operation (partitioning, entanglement, virtualization, etc.) and another optional error-checking operation is performed [1170] to produce the next set of output in step 2. Depending on the workflow, this can result in a vOTP [1180], or virtualized partitioned OTP [1183], or other combinations. Another step (step n [1188]) could be performed, in which another partitioning/entanglement/virtualization operation is completed on the data. In workflow A [1110], this would produce a virtual, entangled OTP (veOTP, or generically referred to as a vOTP [1190]). Finally, another operation is performed [1192] on the OTP data to result in the final working OTP [1194], which can include an eOTP [1196], virtualized, virtualized, entangled OTP (vveOTP, or generically referred to as a vOTP [1199]), or a vOTP or eOTP, among other possibilities.
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[0141] In phase 2, information can be encrypted or decrypted simultaneously, and authentication and/or certification can also take place. A create random index function [15068-15070], and a next index function [15072-15078] is provided which allows randomly created indices to be incrementing from the assigned random position within each of the OTP's dimension range's permissible values. Ranges of data in the multidimensional OTP are iterated through using the NEXT_RANGE function [15081-15087] to prevent cryptanalysis or replay attacks. This function finds the next usable range of indices in the OTP for the encryption/decryption process, allocating new ranges [15083] until full and then extending an existing range [15084-15085] until it merges with another range. The basic encryption function is also the decryption function and consists of simply XORing a single value in a given piece of data with OTP data using a given virtual dimension VDIM and virtual index VINDEX [15093]. This function is called repeatedly in the ENCRYPT_TEXT function until the required piece of information is encrypted [15095-15097]. In this function, the PACK operation compresses and cloaks the number and arrangement of each dimension's index bits in the publicly visible index to the minimum [15102] without revealing the number of bits used to index each dimension [15101] shared privately during phase one. This occurs in the function ENCRYPT_MSG [15100] where the ENCRYPT_TEXT function is called [15104]. After a random amount of encryption [15111] the function will start to encrypt a new or extended range within the OTP. The decryption occurs when the DECRYPT_MSG function calls ENCRYPT_TEXT [15110-15111] being its own reciprocal function. Certification of information occurs in CERTIFY function [15114-15118] which calls the ENCRYPT_MSG function [15100]. If OPT_MODE is set to enhanced, ENCRYPT_MSG is called again [15118]. Authentication is performed in a function [15120-15123] where DECRYPT_MSG is used to process a given piece of token text TOKENTEXT. Note that the token text is derived from the OTP data, and there are certain demarcated ranges within the OTP for authentication. Demarcation prevents multiple requests being made for token text which could be used to provide data for cryptanalysis. If OPT_MODE is set to enhanced, then DECRYPT_MSG is called again.
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[0147] The authentication process can also be expanded to involve more complex methods and approaches, such as two and three way authentication using a device identity (device ID), and/or shared group identity when sent between the sender(s) and receiver(s) using QSE In this process, a sender's challenge process is performed to authenticate the identity (which can include the device ID and/or group ID) of the receiver device(s) to be challenged by sending a QSE message/data containing a challenge key which is the result of an operation (such as an XOR operation) between the identity of the receiving device(s) to be challenged and a random challenge nonce. The receiver's response process, which occurs when the receiver is responding to a sender's challenge message, with a QSE challenge response message/data containing the result of the receiver's device/group identity XORed (or another operator) with the sender's challenge message/data to recover the sender's original random challenge nonce from the sender's challenge key. This is subsequently returned to the sender. The sender's authentication process, which involves receiving the receiver's response message and confirms if the sender's random challenge nonce and the receiver's recovered challenge nonces match (as any other receiver's device/group identity will not recover the senders challenge nonce). In the optional receiver response process, which involves responding to the sender's challenge, the receiver also challenges the sender's device identity. In this process, the receiver's challenge response message also contains/appends a challenge message containing a key being the product (preferably XOR) of the sender's device/group identity to be challenged and a receiver's random challenge nonce. In the sender's challenge response, which involves a reply to a receiver's random challenge message/data with a QSE challenge response message containing the result of the sender's device/group identity XORed (or using another operator) and the receiver's challenge message to recover the receiver's original challenge nonce from the receiver's challenge key which is returned to the receiver. The receiver's authentication process involves receiving the sender's challenge response message/data and confirms if the receiver's original random challenge nonce and the sender's recovered challenge response nonces match (since any other sender's device/group identity will not recover the receiver's challenge nonce). Optionally, during the authentication process, a sender or receiver, challenge or response processes may append an additional arbitrary size random nonce for each challenge and response to increase the effective size of device identity thereby reducing either the possibility of replay attacks or identity collisions caused by similar but incorrect OTPs accidentally responding by chance. Another optional process which can be undertaken during authentication is that sender or receiver, challenge or response processes may use QSE twice or more to encrypt the challenge/response messages thereby hiding the challenge response sequence and further obscuring the sender's/receiver's identity.
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[0152] Typical applications of this system are in mobile cellular phones, telephony and communications including television and radio broadcasts, network devices such as gateways, routers, firewalls and VPN, personal computers, general purpose servers, file servers, web servers, database servers and other systems or electronic devices. A further implementation takes highly integrated circuits and places them in identity devices such as RFID, remote sensing and identity devices like credit cards, identity cards, passports to allow authentication of identity. Extremely low power versions of the implementation are possible, enabling operation with low power or transient power sources such as electro/electromagnetic/magnetic field, solar, or electro/static/voltaic sources, like bi-metallic, aircell, chemical battery, piezo or curie effect. Very low power implementations with the encryption logic designed in hardware gates and registers requires little or no programming. Consequently, the speed and latency of operation is fast, fixed and predictable or with low jitter, required for precise timing of highly synchronized processed such as cellular phone signaling, financial transactions and ledgers where accurate precision timing is used to arbitrate access to resources or records. Time division of resources with long operational life in decades makes the implementation suitable for both terrestrial and satellite communications. A final implementation example takes a version of the highly-integrated logic/circuit design and provides a hardware logic library (like Verilog or VHDL) to enable inclusion into the hardware of a microprocessor or similar devices. The library allows the adaptation of a general-purpose processors such as the ARM processor so a quantum encryption engine can be added to a provide a specialized single chip solution. Ultimately the encryption engine implementation may be included as a standard feature of any electronic processor/CPU.
APPENDIX—MATHEMATICAL MODELLING
[0153] The embodiments of the invention are comprise a method in which large random bit strings (herein referred to as vectors) are created from an original random vector derived from a true random number generator, such as a quantum random number generator. The algorithm uses OTPs which are information theoretic secure, as well as secure key reuse that is combinatorically secure. This appendix will outline key properties of the methods in accordance with embodiments of the invention, including: (1) the preservation of optimal randomness: mixing vector data, when derived from a uniformly random distribution, preserves the properties of the distribution. (2) ensuring that there is no key repetition during the virtualization procedure of the algorithm, using a seeded set selection technique and a bound on virtualization, (3) how attempts to compromise encryption through the biasing of set selection will not be successful (with reasonable assumptions), (4) the probability that an attacker could gain access to insecure message text given a certain amount of intercepted ciphertext produced in a combinatorially secure way, and that this probability is unphysically (when using reasonable parameters).
[0154] Here we will examine the XOR function and its ability to preserve randomness, and show how it can function as a mixing function. The truth table for the XOR function can be defined in equation 2:
when calculating the result of the XOR function, the variables a and b are binary vectors of length ρ (i.e. A, B∈{0,1}.sup.n). The result of an XOR function between the two vectors can be defined as the bitwise operation between the i.sup.th element of vector A and the i.sup.th element of vector B, to produce another binary vector of length ρ.
[0155] To illustrate that the XOR operation preserves randomness, consider a fixed vector F, which can be defined as F∈{0,1}.sup.ρ and another vector R which is chosen from a uniformly random distribution (derived from a true random number generator or some other means) where the probability of each individual binary element in the vector 2.sup.ρ can be defined as 2.sup.−ρ. The result of XORing the vectors F and R can be defined as O, such that:
O=F⊕R (Equation 3)
[0156] We can define the probability that O assumes an arbitrary value as follows:
P(O=Arbitrary) (Equation 4)
which is then defined as
=P(F⊕R=Arbitrary) (Equation 5)
which is then equivalent to
=P(R=F⊕Arbitrary) (Equation 6)
[0157] This can be stated because of the following relationships:
1)O=AA=[0].sup.ρ (Equation 7)
2){O}.sup.ρ⊕A=A (Equation 8)
∀A∈{0,1}.sup.ρ (Equation 9)
[0158] Hence, the probability of the vector O assumes a specific value is equivalent to the probability of R assumes a specific value. As a result, the following can be asserted:
P(O=Arbitrary)=P(R=F⊕Arbitrary)=2.sup.−ρ (Equation 10)
since all of the values of R are equiprobable by definition. Hence, the distribution of values of a given vector combined with another vector of values with a uniformly random distribution using the XOR operation will be a random distribution of values as well (assuming that the two input vectors are independent). This observation can be extended to a set of n vectors, such can then be combined using a series of XOR operations in the following fashion:
O=R⊕A.sub.1⊕A.sub.2⊕A.sub.3 . . . ⊕A.sub.n (Equation 11)
where A.sub.m is an arbitrary value. We can then define:
F=A.sub.1⊕A.sub.2⊕A.sub.3 . . . ⊕A.sub.n (Equation 12)
hence for a given number of vectors n combined using the XOR operator, if at least one vector is of a random distribution, the final result will also be of a random distribution.
[0159] Having establishing that vector combinations from a uniformly random distribution of values can constitute a valid source of new random vector data, a method of selecting sets of information securely must be established. In the encryption algorithm, random vector information which constitutes an OTP is “virtualized” or transformed into a “complex space” which can consist of hyperdimensional space, a network, graph, vector space, or other space as defined previously. The complex space has a coordinate system associated with it, and subsets of the space need to be selected so that no information is revealed about the final or initial key. The initial key is used to guide the selection of subsets in a deterministic fashion. This process will allow one or more parties with the initial key to reconstruct the same final key, used for encrypting the message, which is much larger.
[0160] For instance, consider a complex space with N entries, and each entry consists of a p length vector that is generated using a true random number generator, like a quantum random number generator. The unique index for each location, stored in m bits, can be defined using the following equation:
m=Log.sub.2(N) (Equation 13)
[0161] The walk is initiated by storing the location of the first m bits of a key in a temporary set. The entry to the next location is then provided by XORing the m bits of the initial key with the first m bits of the entry. The product of the XOR operation will produce a result that is of a uniformly random distribution as discussed in section 1.
[0162] This process is repeated at new locations in the complex space, with each entry added to the temporary stored set, until the set contains n desired elements. Then, the resulting n p vectors are XORed together resulting in p bits of the final key. The temporary set is then cleared and the portion of the final key is stored. Then, m bits are discarded from the initial key, and subsequently m bits are retrieved to be processed in the same fashion. During this process, the refresh rate for generating the initial key can be changed to correspond to the appropriate key generation rate.
[0163] When selecting a set of n items, the probability of selecting that set can be expressed as the product of the probabilities of selecting each individual item:
P.sub.set=Π.sub.iP.sub.i (Equation 14)
[0164] The probability of selecting each item can be described as
as each of the m bits obey a uniformly random distribution. The selection of each item is therefore equiprobable, so each set is trivially equiprobable and can be described as:
[0165] This method provides access to all possible subsets within the complex space equally, and the method of subset selection results in no structure in the final key. It is important to note, however, that the set of all chosen subsets has a uniformly random distribution in numerical values, since any two subsets with a nonzero union can be described as having a higher probability of equality compared to two disjoint subsets. This is because the union will have overlap (see
[0166] If we define a complex space of N elements, with a given precision ρ (which can also be referred to as “bit depth”), and a general subset of n elements (n<N), a structure less random walk can be described in the following fashion. We need to define two spaces, a “bit space” and “combination space”. The definition of the “bit space” is a space containing all possible binary vectors of length ρ, and the size of the space is specified by 2.sup.ρ. The “combination space” contains all possible combinations of n elements contained in an N-dimensional complex space. This has a multiplicity defined by a binomial coefficient (without repetition):
[0167] Since the XOR operator is commutative, unordered combinations should be considered rather than ordered permutations. If the combination space size exceeds the bit space size, then this results in multiple combinations of n elements (from N) which when combined result in the same key. As an example, if we have a list consisting of 10 4-bit strings, then this results in 220 possible ways to select various subsets of 3 elements with replacement. The corresponding dimension of the bit space is 2.sup.4=16, and the 16 possible strings are produced on the average, 220/16=13.75 distinct subsets. Hence, certain vectors will occur more likely than other vectors in a complex space. We can define an expectation value which expresses the number of sets which lead to a specific vector as:
which applies to all possible vectors, and selecting certain values for n and ρ can result in:
yielding an expectation within a given complex space of one set per string with size ρ bits.
[0168] There are constraints on this process, including physical memory requirements and time to perform multiple XOR operations. With regard to physical memory, the total amount of memory that needs to be used is related to the number of bits that need to be stored at a given time in the complex space, and as well as the locations of temporary sets, with the physical memory (a reasonable physical memory limit might be 10.sup.10 bits) P being defined as:
N.Math.ρ+n.Math.log.sub.2(N)≈P (Equation 19)
[0169] Additionally, to combine n elements, n.Math.ρ bitwise XOR operations need to be performed. If we define the time to perform an XOR operation as tau, then the time to produce a single bit of key n can be defined as:
T=n.Math.τ (Equation 20)
[0170] Hence, if n is very large, the bitrate reduces. For the remainder of this discussion, r will be assumed to be small enough to render this an insignificant problem. While the combination space can be maximized when n=N/2, this may be difficult to implement practically. In order to impart a combinatorial advantage, we need the combinatorial space to be larger than N, such that:
[0171] A realistic example can be now developed considering the memory and time/bitrate constraints discussed above. If we allocate 1 GB of storage (10.sup.10 bits) filled with vectors with N=10.sup.6 and a depth of ρ=10.sup.4. We can define the combination space with n=861 as:
[0172] And the bit space has a size defined as:
2.sup.10.sup.
[0173] This describes an approximate equivalence between bit space and the combination space. This can be recalculated if sets are recorded and eliminated while running, which would yield about 10.sup.4*10.sup.3010=10.sup.3014 bits of key available, an astronomical value which completely dwarfs all known data storage capacity. A key growth expansion factor, which needs to be defined due to the requirement of refreshing the initial key, can be defined as:
[0174] With the value j defined as the number of refreshes per set, and j=1 yields a factor of 500 bits of final key per bit of initial key.
[0175] The above discussion has shown that spatial distributions of selected subsets in within complex space can be described as uniformly random. However, the values in each subset, namely the XOR product of all elements, may not be numerically uniformly distributed, since some complex space subsets have nonzero unions, which are always equal. While the XOR product of all of the elements in a single subset creates a random value which is treated as a uniformly random event, the probability of a “collision” (or two selected subsets producing the same value) depends on the size of the union. As a result, the keys used are not maximally entropic, resulting in some reuse in the protocol. This can be demonstrated in the following example which involves a complex space with two entries, denoted A and B. A scheme where all of the combinations are used can be expressed as follows:
A⊕M.sub.1=C.sub.1 (Equation 25a)
B⊕M.sub.2=C.sub.2 (Equation 25b)
A⊕B⊕M.sub.3=C.sub.3 (Equation 25c)
[0176] An attacker can gain access to an XORed data using a brute force attack without the presence of a key, which is susceptible to frequency analysis:
C.sub.1⊕C.sub.2⊕C.sub.3=A⊕M.sub.1⊕B⊕M.sub.2⊕(A⊕B⊕M.sub.3)=M.sub.1⊕M.sub.2⊕M.sub.3 (Equation 26)
[0177] The combinations of ciphertext remain secure if there is one string of unknown key data, with one string of maximally entropic key data sufficient to secure the data against crib drag, brute force attack, frequency analysis, and other cryptanalysis methods. To determine the probability that an attacker or some external person could access or decrypt XORed data that is susceptible to frequency analysis, we need to calculate the probability that combinations of compromised ciphertext will completely cancel the key present in another compromised ciphertext.
[0178] To address this problem, we assume that the key can be drawn with equal probability from all sets of complex space elements (i.e. using a structure less random walk). With this assumption, we can count the number of possible multisets G of size |G| (where repetition is allowed in G) of complex space elements that cancel out a set of size |S| (with no repetition allowed in S). S is a set of complex space elements that represent the XOR product that produced a key for ciphertext that was intercepted. G represents the set that consists of the XOR product of multiple keys of other intercepted ciphertexts. This is a larger set of XORed complex space elements that allows for repetition.
[0179] To allow for frequency analysis, two conditions need to be fulfilled for a set G to cancel out a set S. The first condition specifies that every element of S must be contained in G an odd number of times. This condition ensures that the final product of the XOR operation does not contain elements contained in S. In the second condition, each element in the complex space that is not in S must be contained in G zero times or an even number of times. This ensures that no new complex space elements are introduced when S is XORed with G. This problem can be represented in the following fashion: an integer can be assigned to each location within a complex space such that each integer represents the number of times that a location appears in G. If we define the size of a complex space as |H|, the ordered sum of |S| odd integers, and the ordered sum of |H|−|S| even (or zero) integers that sum to |G| represent a unique, unordered set G. This set G cancels some set S.
[0180] Using these principles, we can define the number of integer constructions, or the number of ordered integer sums that equal a particular value. Odd integer constructions of k elements that add to n are expressed as:
[0181] For
an integer, and zero if otherwise. We can then express number of even integer (including zero) constructions of n with k elements as:
[0182] For n even, and zero if otherwise. Hence, the total sets G that will cancel out a set S is defined as follows:
and all fractional expressions are integers, or else the term does not contribute. This can be expressed as a probability by dividing the sum terms by total possibilities, |H| multichoose |G|:
[0183] Using numerical modelling one can calculate reasonable values for the complex space. From the plot
[0184] To determine how much ciphertext can be sent in this fashion with the assumption that not a single breaking set is even is more complicated to determine: C packets of intercepted ciphertext results in a number of unordered sets of size i given by
Hence a breaking set of i.Math.|S| elements is available when
for some value i. For modest values of C, P.sub.break dominates, and i=2 is maximal, but as C increases this is no longer necessarily true as the function
outpaces P.sub.break with an increase in i.