Source: http://www.google.com/patents/US7936869?dq=ascentive
Timestamp: 2015-03-05 15:13:55
Document Index: 452324409

Matched Legal Cases: ['Application No. 60', 'Application No. 60', 'arty 202', 'arty 204', 'arty 204', 'arty 202', 'arty 204', 'arty 204', 'arty 204', 'arty 204', 'arty 302', 'arty 202', 'arty 202', 'arty 302', 'arty 302', 'arty 202', 'arty 302', 'arty 202', 'arty 302', 'arty 202', 'arty 302']

Patent US7936869 - Verifying digital signature based on shared knowledge - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inAdvanced Patent SearchPatentsA method of verifying a digital signature of a first party that was generated using an elliptic curve digital signature algorithm (ECDSA) includes the steps of receiving a public key from the first party; receiving a digital signature from the first party, the digital signature being for an electronic...http://www.google.com/patents/US7936869?utm_source=gb-gplus-sharePatent US7936869 - Verifying digital signature based on shared knowledgeAdvanced Patent SearchPublication numberUS7936869 B2Publication typeGrantApplication numberUS 11/161,558Publication dateMay 3, 2011Filing dateAug 8, 2005Priority dateJan 7, 2005Fee statusPaidAlso published asUS20060153366Publication number11161558, 161558, US 7936869 B2, US 7936869B2, US-B2-7936869, US7936869 B2, US7936869B2InventorsCurtis Linn BeesonOriginal AssigneeFirst Data CorporationExport CitationBiBTeX, EndNote, RefManPatent Citations (104), Non-Patent Citations (51), Referenced by (1), Classifications (18), Legal Events (3) External Links: USPTO, USPTO Assignment, EspacenetVerifying digital signature based on shared knowledge
This application claims priority to U.S. Provisional Patent Application No. 60/641,957 filed Jan. 7, 2005 entitled �Soft Token: Offset Inventions,� and U.S. Provisional Patent Application No. 60/641,958 filed Jan. 7, 2005 entitled �Soft Token: Passphrase Inventions,� the disclosures of which are incorporated by reference herein in their entireties.
1. U.S. Patent Application �ASYMMETRIC KEY CRYPTOSYSTEM BASED ON SHARED KNOWLEDGE� filed on Aug. 8, 2005; 2. U.S. Patent Application �PROVIDING DIGITAL SIGNATURE AND PUBLIC KEY BASED ON SHARED KNOWLEDGE� filed on Aug. 8, 2005; 3. U.S. Patent Application �DIGITAL SIGNATURE SYSTEM BASED ON SHARED KNOWLEDGE� filed on Aug. 8, 2005; 4. U.S. Patent Application �SOFTWARE FOR PROVIDING BASED ON SHARED KNOWLEDGE PUBLIC KEYS HAVING SAME PRIVATE KEY� filed on Aug. 8, 2005; 5. U.S. Patent Application �PROVIDING CRYPTOGRAPHIC KEY BASED ON USER INPUT DATA� filed on Aug. 8, 2005; 6. U.S. Patent Application �GENERATING PUBLIC-PRIVATE KEY PAIR BASED ON USER INPUT DATA� filed on Aug. 8, 2005; 7. U.S. Patent Application �GENERATING DIGITAL SIGNATURES USING EPHEMERAL CRYPTOGRAPHIC KEY� filed on Aug. 8, 2005; 8. U.S. Patent Application �FACILITATING DIGITAL SIGNATURE BASED ON EPHEMERAL PRIVATE KEY� filed on Aug. 2005; and 9. U.S. Patent Application �DIGITAL SIGNATURE SOFTWARE USING EPHEMERAL PRIVATE KEY AND SYSTEM� filed On Aug. 8, 2005. COPYRIGHT STATEMENT
There are two principal types of cryptosystems: symmetric and asymmetric. Symmetric cryptosystems use the same key (a secret key) to encrypt and decrypt the message. Asymmetric cryptosystems use one key (for example a public key) to encrypt a message and a different key (a private key) to decrypt the message. Asymmetric cryptosystems are also called �public key� or �public key/private key� cryptosystems.
Symmetric cryptosystems have the following inherent problem: how does one transport the secret key from the send of a message to the recipient securely and in a tamperproof fashion? If someone could send the secret key securely, then in theory he or she would not need a cryptosystem in the first place�the secure channel could be simply used to send the message. Often, trusted couriers and digital certificates are used as a solution to this problem. Another method for communicating symmetric keys (as well as messages) is the well-known RSA asymmetric public key cryptosystem, which is used in the popular security tool Pretty Good Privacy (PGP).
Public key/private key cryptography has at least three principal applications. First is basic encryption�keeping the contents of messages secret. Second, digital signatures are implemented using public key/private key techniques. U.S. Pat. Nos. 6,851,054; 6,820,202; 6,820,199; 6,789,189; and others, the disclosures of which are incorporated by reference herein, are examples of digital signature type systems that utilize aspects of public key/private key cryptography. Third, electronic authentication systems that are not based strictly on conventional digital signature techniques may be implemented with public key/private key cryptography. Some of the foregoing incorporated and referenced patents describe certain aspects of such authentication systems.
In implementing ECC and, specifically, in generating an asymmetric public-private key pair for use in the Elliptic Curve Digital Signature Algorithm (ECDSA), an elliptic curve is defined by certain �domain� parameters, and a point is chosen along the elliptic curve that serves as a generator of a finite cyclic group, all the elements of which also lie along the elliptic curve. This generator is referred to as the �generating point� or �base point� (P). The domain parameters include: the field identification (or �Field ID�) identifying the underlying finite or Galois field, traditionally represented as �F2p� or �F2m�; the curve comprising two coefficients �a� and �b� of the elliptic curve equation y2=x3+ax+b mod p; a generating point (xp, yp); and the order of the generating point �n� comprising a prime number. Optionally, the domain parameters may include other specifications, such as, for example, a bit string seed of length 160 bits�if the elliptic curve is randomly generated in accordance with governmental standards, or a cofactor. The domain parameters further may include additional specifications, such as the appropriate bit length of a key.
In certain known methodologies for ECC, after a generating point (P) specified, a first public-private key is first generated essentially by obtaining a large random number (R) from a random number generator or pseudo random number generator; and then using the random number as a �multiplier� of the generating point (i.e., P is repeatedly �added� R times) to arrive at the public key (PuK). The random number multiplier used to generate the public key is the private key (PrK) of the public-private key pair.
As mentioned above, certain known public key/private key cryptosystems typically utilize the random number approach in key generation. However, it is believed that additional security aspects for public key/private key generation can be obtained by utilizing measures other than strictly using a random number during in the key generation algorithms. A deterministic function, as compared to a nondeterministic function, can provide security that is more than adequate for many applications, especially in an elliptic curve cryptosystem, and may provide certain benefits not available in nondeterministic key generation approaches. For example, a deterministic function may be used to assist in securely storing a private key in an electronic device, or in generating a public key/private key pair for use in an �on demand� cryptographic operation in a computer system that itself may not be capable of storing or protecting the private key from access by potential eavesdroppers. Furthermore, a deterministic function can extend the usability of a public/private key pair by making a single private key useable by multiple parties while still being able to show intent between the two parties.
In utilizing ECC�or any other cryptographic system, any cryptographic key used for encryption must be protected from compromise, especially during storage. Otherwise, the integrity of the cryptographic system is jeopardized. For example, if an insecure or network-accessible computer system and/or software is used in connection with a cryptographic operation, there is a risk that the keys stored in that computer system could be obtained and improperly utilized.
Safeguarding cryptographic keys, especially private keys in public-private key cryptographic systems, is important if adoption and use of cryptography by the general public in electronic communications is to become prevalent. The safeguarding of cryptographic keys is especially important in connection with the conduct of electronic transactions such as, for example, financial transactions. Facilitating the adoption and use of cryptography in such electronic communications�especially adoption and use of digital signatures�also is important, as demand for greater security, reliability, and accountability in such electronic communications is believed to be increasing.
More particularly described, certain aspects of the invention(s) relate to the use of the same private key in multiple public-private key pairs that are established for communicating with different parties. Moreover, as will become apparent from the detailed discussions below, the present invention particularly relates to�but is not limited to�elliptic curve cryptography (ECC) and the use of the Elliptic Curve Digital Signature Algorithm (ECDSA). Accordingly, many aspects and features of the present invention relate to, and are described in, the context of ECC, but the present invention is not thereby necessarily limited to such cryptography.
The step of transforming the initial generating point into a new generating point preferably includes the step of generating a transformer as a deterministic function of shared knowledge. In accordance with the invention, and as used herein, the phrase �as a deterministic function of� means that which follows the phrase is an argument of the function. Moreover, the use of �deterministic� to modify function means that the function, given a specific argument or a specific set of arguments of the function (depending on whether the function includes one or more arguments), returns the same result time and time again. It should also be noted that a function could depend upon arguments in addition to that which follows �as a deterministic function of�, i.e., that which follows the phrase is not intended to be an exclusive list of all arguments of the function.
Furthermore, in accordance with the invention, and as used herein, the phrase �shared knowledge� has a defined meaning that is specific to the present application. In this context, shared knowledge means information known to multiple parties that serves as an argument for a deterministic function for transforming a given generating point of domain parameters of, for example, an elliptic curve used in elliptic curve cryptography. The shared knowledge permits each party to independently transform the generating point to arrive at a new generating point for use in elliptic curve cryptography, such as in generating public keys and digital signatures and in verifying digital signatures. Preferably, one of the parties knowing the shared knowledge will be the party that generates a digital signature, and another party will be the party that receives the digital signature and verifies the digital signature with a public key.
In any event, the deterministic function of the shared knowledge�whatever the shared knowledge may comprise�preferably outputs a large integer value constituting a transformer, and the step of transforming the initial generating point into the new generating point preferably includes the step of multiplying, through scalar multiplication, the initial generating point by the transformer to arrive at the new generating point.
In preferred embodiments of this aspect, the method includes the step of clearing from the computer system the new generating point following the step of generating the public key so that the generating point is no longer available within the computer system for regenerating the public key; and the step of exporting the public key from the computer system for communicating to another party. The step of clearing preferably includes overwriting the new generating point wherever it is stored or saved in memory of the computer system. The overwriting preferably includes wiping or writing pseudo random bit strings to the data blocks of the computer memory in which the generating point is saved or stored. Of course, the step of clearing does not necessarily include clearing from a secure data storage memory or device (referred to herein as a �secure store�) associated with a computer system.)
In accordance with an alternative feature of this aspect of the invention, the step of determining the private key includes generating the private key as a deterministic function of user input data (sometimes referred to herein as �UID�) that is received within a computer system of the first party. The UID may comprise, for example, a passphrase, a password, or a PIN. Alternatively, or in addition thereto, the user input data may comprise a biometric characteristic. Furthermore, if the private key is generated within the computer system as a result of user input data, then both the user input data and the private key preferably are cleared from the computer system so that the user input data must be received again within the computer system in order to regenerate the private key for further cryptographic activities. Indeed, because the private key is generated as a deterministic function of the UID, the private key need not be saved in a secure store.
As a preliminary matter, it will readily be understood by one of ordinary skill in the relevant art that the invention has broad utility and application. Furthermore, any embodiment discussed and identified as being �preferred� is generally considered to be part of a best mode contemplated for carrying out the invention. Other embodiments also may be discussed for additional illustrative purposes in providing a full and enabling disclosure of the invention. Moreover, many embodiments, such as adaptations, variations, modifications, and equivalent arrangements, will be implicitly disclosed by the embodiments described herein and fall within the scope of the invention.
Additionally, it is important to note that each term used herein refers to that which a person skilled in the art would understand such term to mean based on the contextual use of such term herein. To the extent that the meaning of a term used herein�as understood by a person skilled in the art based on the contextual use of such term�differs in any way from any particular dictionary definition of such term, it is intended that the meaning of the term as understood by a person skilled in the art should prevail.
Additionally, when used herein to join a list of items, �or� generally denotes �at lease one of the items,� but does not exclude a plurality of items of the list. Thus, reference to �a picnic basket having cheese or crackers� describes �a picnic basket having cheese without crackers�, �a picnic basket having crackers without cheese�, and �a picnic basket having both cheese and crackers.� Finally, when used herein to join a list of items, �and� generally denotes �all of the items of the list.� Thus, reference to �a picnic basket having cheese and crackers� describes �a picnic basket having cheese, wherein the picnic basket further has crackers,� as well as describes �a picnic basket having crackers, wherein the picnic basket further has cheese.�
In preferred system 200, the first party 202 obtains software from the second party 204. The software may be communicated 206 via the Internet 212 from a computer system of the second party 204 as shown in FIG. 2. The software preferably includes the ability to generate public and private keys of a public-private key pair in accordance with the aforementioned preferred methods of the invention, and includes the ability to generate digital signatures using the private key of the key pair, wherein the algorithm utilized to generate the digital signatures preferably is the ECDSA. Furthermore, the elliptic curve parameters�including the generating point�are communicated between the parties 202, 204 and, preferably, are included as predefined parameters contained within the software communicated to the first party 202 by the second party 204.
Identifying information (sometimes abbreviated as �ID�) of the communicated software preferably is included with the software, whereby a communication 208 back over the Internet 212 that includes the identifying information will enable the second party 204 to identify the particular software. The identifying information may include a hash value, and the identifying information may be digitally signed, to provide some measure of insurance to the second party regarding the true identity of the software.
As will be appreciated from FIG. 2, this registration process of preferred system 200 is performed by the second party 204 numerous times with other third parties, whereby the database 210 contains a plurality �n� records, each record including a name associated with multiple public keys and information regarding the software utilized in generating the public keys.
Upon receipt of the information from the second party 204 regarding the public key, the third party 302 may evaluate this information in gauging the risk that either the private key utilized to generate the digital signature was compromised and that the message was not, in fact, sent from the first party 202, or that the message was altered while in transit from the first party 202 to the third party 302. Indeed, a risk level can be assigned and taken under consideration in making a business judgment as to whether�and what�action to take, if any, in response by the third party 302 to receipt of a digitally signed message from the first party 202. The third party 302 further may request this information upon further receipt of digital signatures from the first party 202, or the third party 302 may itself record this information in association with the public key of the first party 202 in a database of the third party 302.
A coordinate in Cartesian space that serves as the center of the circle (A, B) 602; and A radius that defines the boundary of the circle R 604. With these two pieces of information, we can uniquely describe a specific circle and calculate all of the points�i.e. (x, y) coordinates�that make up the circle.
The foregoing information of a center coordinate and radius serves to define the �Domain� of the circle, the make-up of the circle. With respect to elliptic curves, the terms �Elliptic Curve Domain Parameters� are often used to represent the information that defines a specific elliptic curve. Elliptic curve domain parameters serve the same purpose as the A, B and R terms in the above definition of the circle. The �Elliptic Curve Domain Parameters� while containing different values and having different meanings than those for the circle serve the same purpose, i.e. to uniquely define a particular geometric shape. In the discussion of the circle the �Circle Domain Parameters� are A, B and R.
The general conceptual nature of the public key and private key in the field of elliptic curve cryptography is the same as for other forms of asymmetric cryptography. Given one value that can be kept a secret (the private key), the second value that is derived from the first can be made public (public key). The reason that the second value (the public key) can be made public is that the cost to work backwards from the public key to the private key is computationally prohibitive. The other point that is worth noting is that even though the values are both referred to as �keys� does not mean that they are equivalent in use or that the values they represent are the same.
In a circle metaphor, these two pieces of information (a point on a circle 704, angle of the radius 706) can be utilized as a public/private key pair. The angle 706 may be utilized as a private key, while the (X, Y) point 704 may be utilized as the public key. If the radius R 708 is known, the value of the center of the circle (A, B) 702 (which may be considered the data values encrypted) cannot be determined from merely knowing the point (X, Y)�the angle (e.g. 45�) 706 must also be known in order to uniquely define a single point (A, B). Although this example using a circle as conceptually equivalent to an elliptic curve is contrived and computationally simple to break, it should now be understood that public key and private key for use in a cryptographic operation may be derived from a similar operation by using the mathematics of an elliptic curve, much in the same fashion as herein described in connection with the mathematics of a circle.
Many cryptography schemes, including conventional ECC, depend on properties of randomness for the actual generation of key pairs. In the circle metaphor we need to determine an angle that serves as the private key for a key pair and allow us to determine the matching (X, Y) coordinate that will serve as the related public key. The traditional method of generating a private key would be to use a random number in the generation of the angle. For example, we could generate a random number that is greater than −1 and less than 360 and this could serve as our �private key� or �angle�. With this angle we can mathematically determine the corresponding (X, Y) coordinate on the circle that is denoted by the angle. A side effect of using a random number for the generation of the angle is that you must store the angle once it is generated. The reason that the generated angle must be stored is that since it was generated through at Random (using a random number) it would be difficult (next to impossible) to regenerate the same Angle predictably.
At this point we have enough metaphorical information to begin to specifically address the nature of deterministic functions in ECC key generation. The basis of these aspects of the invention is that we are replacing the random number used in key generation with a calculation that can be repeated given the same input. This repeatable calculation is called a �deterministic function�. A deterministic function is a calculation that, given a specific input, will always produce the same output. For example, 2 times X or (2*X) is a deterministic function. If you replace the �X� term with the same number (e.g. 3) you will get a result that can be repeated every time you replace the �X� term with that same number. Thus, the mathematical operation of (2*3) always produces 6, no matter how many times the computation is repeated�the answer will always be 6 when the �X� term is replaced with 3.
In the �passphrase� aspects of the invention, described in greater detail in certain referenced related patent applications, the private key in a private/public key pair is generated through a deterministic function instead of the more traditional method of generating the private key through a random function. The passphrase could be a word a sentence or any string of characters that are memorable to the user. This passphrase serves as the input to a deterministic function that provides as output a value that is suitable for use as the private key. A simple example of a possible implementation of this concept is below (the algorithm and function are illustrative only).
In accordance with certain aspects of the so-called �passphrase� inventions, we first define a set of acceptable characters that can be used to form a passphrase. For our example we will use the common characters: alphabetic/numeric and punctuation. For each allowable character we assign a numeric value that will represent the character in our calculation. This provides a table such as shown in the following example:
Next, a deterministic function is defined that will turn a word, sentence, or any string of characters into a value suitable as a replacement for the random angle value. One example of a deterministic function is to cumulate the numerical values of the characters of an input string (e.g. the word �PassWord�), divide by a predetermined number (e.g. 360), and use the remainder of the division operation as an angle value. Such an exemplary deterministic function would be expressed as follows in conceptual terms:
1. Start with a value of zero in the �Passphrase Work Value�, which is a cumulation data variable. 2. For every character in the input string (e.g. �PassWord�), look up the value corresponding to that character and add it to the value in the data variable �Passphrase Work Value�. 3. When all of the input characters of the string are exhausted, divide the cumulative value in �Passphrase Work Value� by 360, and assign the remainder of this division (Modulo 360) to �Passphrase Angle�. 4. The value or number of the variable �Passphrase Angle� is then utilized as a private key. Assume that the input or passphrase is the string �PassWord� without the quotes. If we start with zero (0) in the �Passphrase Work Value� and take the first character (�P�) of the string and look it up in the above table we find the value 80. Add this value to the �Passphrase Work Value� giving the value 80 for �Passphrase Work Value�. Move to the next character (�a�) in the string and perform the same lookup as before, which yields the value 65. Add the value 65 to the �Passphrase Work Value�, which cumulates to 145. Continue this process until there are no more characters in the input string. In this example, the cumulated values of the passphrase �PassWord� would yield the following computation:
When the input characters of the string �PassWord� are exhausted, the value of 627 remains in the variable Passphrase Work Value. Based upon the definition of our deterministic function, 819 is divided by 360:
The remainder of this division operation is assigned to be the �Passphrase Angle� and may be utilized as a private key in accordance with this example.
FIG. 15, FIG. 16, FIG. 17, and FIG. 18 each illustrates a method for transforming a generating point P of identified domain parameters into a new generating point P′. In each described method, the generating point is transformed as a deterministic function of shared knowledge (sometimes abbreviated herein as �SK�) that is known both to the party generating the public key and the digital signature, and to the party verifying the digital signature. Without both parties knowing the shared knowledge, the same new generating point could not be calculated and the party receiving the public key and the digital signature would be incapable of verifying the digital signature using the public key.
The deterministic function of Step 1904 of method 1900 outputs a value using the UID as an argument of the function. This value represents the private key. The function is �deterministic� because each time the same UID is used as an argument of the function, the same output is received. In the preferred embodiment, the output of the deterministic function in step 1204 preferably is a large integer value. Furthermore, any function that can deterministically generate a suitably large number from an input value can be used as the deterministic function of step 1904 to generate the private key, as a private key for use in ECC is fundamentally any suitably large number. The deterministic function itself may include such algorithms as hashing the UID; hashing multiple times the UID; and hashing multiple times the UID while folding interim hashes together. Moreover, any hashing algorithm used preferably is a strong hash function. As will be appreciated by one having ordinary skill in the art, a strong hash function is a hashing algorithm that is considered secure because it: 1) it is computationally infeasible to find UID that corresponds to a given message digest; and, 2) it is computationally infeasible to find two UIDs that produce the same message digest. Using a strong hash function, any change to the UID will, with a very high probability, result in a different message digest.
The function for generating the digital signature preferably includes appending the indicator to that which is digitally signed such as, for example, an electronic message. The indicator may comprise, for example, either a �1� or �0�appended to the beginning or end of the electronic message. Of course, the indicator also should be communicated to the recipient of that which was digitally signed in order for the recipient to be able to verify the digital signature; however, the indicator need not be communicated if the recipient is aware of the possible values of the indicator and, therefore, can verify the digital signature by checking all possibilities. For example, the recipient of the electronic message and digital signature for the message�which in this case is the digital signature of both the message and the indicator appended thereto�can append the known different possible values of the indicator to the electronic message in verifying the digital signature. One of the different possibilities should result in verification of the digital signature, provided that the message was not changed in transit and that the true private key was used in generating the digital signature.
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ARES 08. Third International Conference on Digital Object Identifier: 10.1109/ARES.2008.20, Publication Year: Apr. 2008 , pp. 723-726.* Cited by examinerReferenced byCiting PatentFiling datePublication dateApplicantTitleUS20130236019 *Apr 27, 2012Sep 12, 2013Gregory Marc ZaveruchaIntercepting key sessions* Cited by examinerClassifications U.S. Classification380/30, 380/282, 705/67, 713/176International ClassificationH04L9/28, H04L9/30, G06Q20/00, H04L9/08, H04K1/00, H04L9/32Cooperative ClassificationH04L2209/56, H04L9/3252, H04L2209/60, H04L9/3066, G06Q20/3674, H04L9/321European ClassificationH04L9/32S, G06Q20/3674Legal EventsDateCodeEventDescriptionOct 24, 2014FPAYFee paymentYear of fee payment: 4Jul 12, 2011ASAssignmentOwner name: WELLS FARGO BANK, NATIONAL ASSOCIATION, AS COLLATEFree format text: SECURITY AGREEMENT;ASSIGNOR:FIRST DATA CORPORATION;REEL/FRAME:026578/0186Effective date: 20110712Aug 8, 2005ASAssignmentOwner name: FIRST DATA CORPORATION, COLORADOFree format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:BEESON, CURTIS LINN;REEL/FRAME:016367/0192Effective date: 20050804RotateOriginal ImageGoogle Home - Sitemap - USPTO Bulk Downloads - Privacy Policy - Terms of Service - About Google Patents - Send FeedbackData provided by IFI CLAIMS Patent Services