Non-repudiation protocol using time-based one-time password (TOTP)

Abstract

A method to validate delivery of a document using a non-repudiation protocol and a time-based one time password (TOTP) for encryption is described. The method includes a one-time registration of an application with a trusted third party, wherein the trusted third party provides a seed to a first device of a first user. The first user receives and accepts a document from a second user. The first device generates the TOTP based on the seed. Using the TOTP as an encryption key, the first device computes a current hash. The delivery of the document can be validated by a second device of a second user based on a comparison of the current clock time and GPS coordinates (optional) of first device as compared to the associated values of the second device. The second device stores the document, first device's computed hash, and current clock time.

Description

FIELD OF THE INVENTION

The present invention relates to methods to validate delivery of documents between two parties, and more particularly, validating delivery of documents using a non-repudiation protocol and a time-based one-time password for encryption.

BACKGROUND

Generally speaking business records (invoices, etc.) are commonly exchanged as paper artifacts. One example would be a consumer packaged goods vendor route sales-person having a portable computing device and printer. Traditionally, the sales-person would print paper invoices containing a record of the products delivered to a retail store. The retail store receiving clerk may “accept” the invoice by stamping the invoice pages with a unique physical inked stamp (and often signing/initialing the stamped area) so that the delivery person has a stamped/signed copy of the invoice to keep for their records.

Therefore, a need exists whereby the paper and inked stamp are obviated, and the documents can be exchanged digitally. The challenge is to provide a substitute method for the paper/stamp method of validating the delivery of a document.

SUMMARY

Accordingly, in one aspect, the present invention embraces a method to validate delivery of a document using a non-repudiation protocol and a time-based one time password (TOTP) for encryption. The method includes a one-time registration of an application with a trusted third party, wherein the trusted third party provides a seed to a first device of the first user. The first user receives and accepts a document from a second user. The first device generates the TOTP based on the seed. Using the TOTP as an encryption key, the first device computes a current hash. The delivery of the document can be validated by a second device of the second user based on a comparison of the current clock time and GPS coordinates (optional) of first device as compared to the associated values of the second device. The second device stores the document, first device's computed hash, and current clock time. As discussed herein, the term “validation” is equivalent to the term “verification”.

In an exemplary embodiment, a method of implementing a non-repudiation protocol by a first device comprises registering, by the first device, an application associated with the first device at a trusted third party. The application registration is a one-time event. The method further includes receiving, by the first device, a seed that was generated by the trusted third party based in part on a seed time; receiving, by the first device, a document from a second device; displaying, by the first device, the received document to a first user. The first user is associated with the first device. The capabilities of the first device and the second device are equivalent, and the first device and second device utilize the same application.

In response to receiving an input from the first user indicating acceptance of the document: computing, by the first device, a time-based one-time password based in part on a current clock time of the first device and the seed; computing, by the first device, a first hash of the document using the time-based one-time password as an encryption key; and transmitting, by the first device, to the second device the first hash, the current clock time the first hash was computed by the first device, and optionally GPS coordinates of the first device. In response to the second device assuming that the current clock time and optionally the GPS coordinates of the second device are within a threshold of the current clock time and optionally the GPS coordinates of the first device, storing, by the second device, the first hash, the current clock time the first hash was computed by the first device, and optionally the GPS coordinates of the first device.

In response to the second device not assuming that the current clock time and optionally the GPS coordinates of the second device are within the threshold of the current clock time and optionally the GPS coordinates of the first device, measuring, by the second device, to verify that the current clock time and optionally the GPS coordinates of the second device are within the threshold of the current clock time and optionally the GPS coordinates of the first device. In response to the second device failing to verify that the current clock time is within the threshold of the current clock time of the first device, calibrating, by the first device, the device clock time of the first device.

The method further comprises, in response to receiving an input from the first user indicating non-acceptance of the document, transmitting, by the first device, the document to the second device to request a correction. The method further comprises, in response to the current clock time of the first device not being within the threshold of a current clock time of the second device, receiving, by the first device, a rejection from the second device. And, the method further comprises, in response to the GPS coordinates of the first device not being within the threshold of a GPS coordinates of the second device, receiving, by the first device, a rejection from the second device.

The method further comprises: disputing, by the first device, reception of the document or asserting that the document has subsequently been altered; transmitting, by the first device, an indication of the dispute or assertion to the trusted third party via the second device, causing the trusted third party to: (1) receive, from the second device, an identity of the first device, the document, the first hash of the first device, and first device's reported time the first hash was computed; (2) compute another time-based one-time password of the first device based in part on the reported time the first hash was computed using the seed provided to the first device; (3) hash the document with the another time-based one-time password to generate a second hash; (4) compare the first hash to the second hash; and (5) determine that the document provided by the second device is legitimate if the first hash and the second hash are equal.

The method further comprises: transmitting, by the first device, an indication of the dispute or assertion to the trusted third party via the second device, causing the trusted third party to determine that the document provided by the second device is not legitimate if the first hash and the second hash are not equal. And the method comprises generating a digital signature based on the first hash. The document is acceptable when the first user manually determines accuracy of content of the document. After registration neither the first device nor the second device accesses the trusted third party unless and until there is a dispute.

In another exemplary embodiment, a method of implementing a non-repudiation protocol by a first device comprises receiving, by the first device, a document from a second device. In response to receiving an input from a first user indicating acceptance of the document: (1) computing a time-based one-time password based in part on a current clock time and a seed; (2) computing a hash of the document using the time-based one-time password as an encryption key; and (3) transmitting the hash, and the current clock time the hash was computed to the second device, wherein, the second device stores the document, the hash, and the current clock time the hash was computed by the first device.

The method further comprises registering, by the first device, an application at a trusted third party; and receiving, by the first device, the seed that was generated by the trusted third party based in part on a seed time. The application registration is a one-time event. The method further comprises receiving, by the first device, a verification from the second device that the first device's current clock time is within a threshold of the second device's current clock time. Further, the method includes transmitting, by the first device, GPS coordinates to the second device; and receiving, by the first device, a verification from second device that the GPS coordinates of the first device are within a threshold of second device's current GPS coordinates.

The method also comprises, in response to receiving an input from the first user indicating non-acceptance of the document, transmitting, by the first device, the document to second device to request a correction. If the current clock time of the first device is not within a threshold of the current clock time of the second device, not storing the document, the hash, and the current clock time the hash was computed by the first device. The method also includes generating a digital signature based on the first hash. And, the method includes calibrating a clock time of the first device using a phone time/network time protocol. The document is acceptable when the first user manually determines an accuracy of content of the document.

In yet another exemplary embodiment, a method of implementing a non-repudiation protocol by a first device comprises: (1) receiving a request for a document from a second device; (2) transmitting a document to the second device; (3) receiving a hash, and a current clock time the hash was computed by the second device, wherein, the second device computes a time-based one-time password based in part on the current clock time and a seed that was received from a trusted third party, and wherein, the second device computes the hash of the document using the time-based one-time password as an encryption key; (4) verifying that the current clock time of the second device is within a threshold of a current clock time for the first device; and (5) storing the document, the hash, and the current clock time the hash was computed by the second device.

The first device and the second device are both capable of communicating with each other by: utilizing the same application to register and obtain the seed from the trusted third party, and creating a unique ID each time they send a communication to the other party, wherein, the unique ID is based on hash information and current clock time information. If the first device or the second device initiates a dispute, the initiator of the dispute engages the trusted third party to determine whether the document is legitimate.

The foregoing illustrative summary, as well as other exemplary objectives and/or advantages of the invention, and the manner in which the same are accomplished, are further explained within the following detailed description and its accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In an exemplary embodiment, FIG. 1 illustrates a document exchange between two trading partners, supported by a trusted third party.

In an exemplary embodiment, FIGS. 2A and 2B illustrate a flowchart for a method of a document exchange and validation based on a non-repudiation protocol and a time-based one time password (TOTP) for encryption.

In an exemplary embodiment, FIG. 3 illustrates a flowchart for a method of dispute resolution between two trading partners.

DETAILED DESCRIPTION

The present invention embraces a method to validate delivery of a document using a non-repudiation protocol and a time-based one time password (TOTP) for encryption.

Business partners exchanging business records (invoices, purchase orders, etc.) digitally/electronically can require a method whereby the transmission/receipt of the document and the integrity of the document can be provably verified by a third-party (usually a judge or arbitrator), and neither trading partner can falsely claim non-receipt/non-transmission or tampering after the document has been exchanged and accepted. This barrier to false claims is commonly referred to as “non-repudiation”.

Current non-repudiation protocols can require extensive event logging, time synchronization, public/private key management, and real-time interaction with a trusted third-party. For business document exchanges involving lesser monetary (or other) values, a lighter-weight non-repudiation method may be desirable to better match the security requirements with the business need.

The present invention can reduce the infrastructure and management burden of implementing a non-repudiation protocol. Unlike prior art, the present invention can offer the following benefits: 1) there is no need for an on-line connection to a trusted third-party (TTP) during document exchange, 2) there is no need to distribute (and manage) private encryption keys to trading partner devices, and 3) there is no need for sophisticated/secure time/clock synchronization. Current art can require an on-line interaction with a TTP for each document exchange. The present invention may only require a one-time setup interaction with the TTP to configure each trading partner. Thereafter, interaction with the TTP may not be required during document exchange, and may only be required in the event of a trading partner dispute (i.e. if one of the trading partners claims non-receipt/non-transmission or document tampering).

Instead of static private encryption keys, a time-based password algorithm may be used to generate temporal encryption keys to be used during each document exchange. The present invention describes the novel use of TOTP algorithms as the private key generation mechanism in the general non-repudiation process.

Non-repudiation protocols aim at preventing parties in a communication from falsely denying having taken part in that communication; for example, a non-repudiation protocol for digital certified mail can ensure that neither the sender can deny sending or transmitting the message, nor the receiver can deny receiving it. Some aspects of Non-repudiation protocols are disclosed in the following paragraphs.

Non-repudiation of Origin (NRO) or Evidence of Origin is supplied by the originator. NRO provides the recipient with proof of origin and guards against the originator of a message falsely denying having sent the message.

Non-repudiation of Receipt (NRR) or Evidence of Receipt (EOR)—supplied by the recipient, which guards against the recipient of a message falsely denying having received the message.

Non-repudiation of Delivery (NRD)—supplied by the delivery agent, this provides the originator of the message with evidence that the message has been delivered to the recipient.

Non-repudiation of submission (NRS)—supplied by the delivery agent, which provides the originator of the message with evidence that the message has been submitted for delivery to the recipient:

• • NRO=sSA(fNRO; B; L; C)
  • NRR=sSB(fNRR; A; L; C)
  • sub K=sSA(fSUB; B; L; K)
  • con K=sST (fCON; A; B; L; K)
  • 1: A ! B: fNRO; B; L; C; NRO
  • 2: B ! A: fNRR; A; L; NRR
  • 3: A ! TTP: fSUB; B; L; K; sub K
  • 4: B $ TTP: fCON; A; B; L; K; con K
  • 5: A $ TTP: fCON; A; B; L; K; con K

In step 1, A contacts B and sends the encrypted message. In step 2, B confirms receipt, but cannot read the message. In step 3, A submits the message key to a trusted third party; sub K is the proof of submission of K. The trusted third party stores the tuple (A; B; L; K; con K) in some read-only directory accessible to the public; con K is the confirmation of K issued by the TTP. Then, in step 4, B gets the key while, in step 5, principal A confirms that B can indeed get the key. The last two steps can be performed in any order.

TOTP is a time-based one time password, a temporary passcode, generated by an algorithm from a secret key (e.g. a seed provided by TTP) and current time. The algorithm that generates this passcode uses the current time of a day as one of its factors ensuring that each passcode is unique. Algorithm combines secret key with current timestamp using cryptographic hash function to generate one-time password. TOTP are commonly used for two-factor authentication like Google Authenticator Application, Amazon web services (AWS Virtual MFA) etc.

A hash of the document can be utilized to generate a digital signature. Digital signatures can provide the added assurances of evidence to origin, identity, and status of an electronic document, transaction or message, as well as acknowledging informed consent by the signer. Digital signatures are based on public key cryptography, also known as asymmetric cryptography. Using a public key algorithm such as RSA, one can generate two keys that are mathematically linked: one private and one public. To create a digital signature, signing software (such as an email program) creates a one-way hash of the electronic data to be signed. The private key is then used to encrypt the hash. The encrypted hash—along with other information, such as the hashing algorithm—is the digital signature.

For the present invention, the validation process can be described with the following elements: TOTP=Time-based One-time Password, TTP=Impartial Trusted Third-Party, TPA=Trading Partner A, the originator of the document (second user), TPB=Trading Partner B, the receiver of the document (first user). As used herein, TPA is a device that is associated with a user, e.g., second user. TPB is a device that is associated with a user, e.g., first user. Also, as used herein, the term validation” is equivalent to the term “verification”.

Both TPA and TPB can be using computer applications (usually on mobile devices) that contain the document review, exchange, and acceptance logic. The communication between the devices can be accomplished using a variety of industry standard file transfer or other data communication protocols. The present invention may not require any special cryptographic hardware—it can use only general computing hardware.

The validation method can include a one-time application registration with TTP system being initiated by TPB: a) TPB uses the application to log into the TTP-provided server application using pre-arranged credentials. b) The TTP notes the current time and creates an initial encryption “seed” for TPB (known only to TTP and TPB) and sends the seed value to TPB to be securely stored on the computing device used by TPB; c) This operation can be performed only one time as an initial setup step, and may not be required for any subsequent document exchange.

After the one-time initial set-up, the validation method can include the TPA electronically sending or transmitting a document to TPB: a) a user of TPB reviews the document for accuracy and, if OK, the user of TPB proceeds to digitally accept the document; b) TPB computes the current TOTP based in part on the current time and the initial seed; c) TPB computes a cryptographic hash of the document using the TOTP as the encryption key; d) TPB sends the computed hash and its current clock time (and optionally, TPB's current GPS coordinates) back to TPA; e) TPA can optionally validate that TPB's current time and GPS coordinates are within a reasonable threshold of TPA's current time and GPS location and reject the validation. If they are not validated, TPB can calibrate its device time using the Phone time/NTP (Network Time Protocol) and ensure GPS location services are turned on. TPB also can use Assisted GPS (AGPS) for better accuracy; f) TPA stores the original document, TPB's computed hash, and TPB's reported clock time and GPS coordinates.

In the case where the user of TPB later claims to not have received the document or that the document has subsequently been altered (or as a periodic audit), the following method can be used to resolve the dispute between the user of TPB and the user of TPA: 1) TPA sends TPB's identity, the original document, TPB's computed hash, and TPB's reported time to the TTP. In a more formal legal setting, this information may be provided to a judge or arbitrator for transmission to the TTP; 2) The TTP attempts to validate the document 2a) The TTP computes the TOTP for TPB as of the reported time of the document exchange; 2b) The TTP hashes the supplied document with the computed TOTP; 2c) The TTP compares the computed hash to the hash supplied by TPA (as originally supplied to TPA by TPB during the original document exchange; 3) The TTP reports the results of the hash comparison to all parties.

If the hashes match, then depending upon the length of the TOTP (the length having been configured to match the desired level of cryptographic strength), it can be cryptographically infeasible (a term in the art) for TPA to have forged a document having the same cryptographic hash as the original document.

In an exemplary embodiment 100, FIG. 1 illustrates a document exchange between trading partner A 104 (TPA 104) and trading partner B 106 (TPB 106), supported by a trusted third party 102 (TTP 102). TPB 106 communicates with TTP 102 during a one-time registration and obtains an initial “seed” to support the calculation of a time-based one-time password (TOTP). (FIG. 1, 110) After the one-time registration, TPA 104 transfers a document to TPB 106 in document exchange 112. TPB 106 computes a current TOTP based on the “initial seed” and a current time. Then, TPB 106 computes a hash of the document using TOTP as the encryption key, and transmits to TPA 104 the hash, current clock time and GPS coordinates.

TTP 102 communicates with TPA 104 only during a dispute resolution. (FIG. 1, 108). TTP 102 does not communicate with TPA 104 during the document exchange 112 and validation. TTP 102 communicates with TPB 106 during a one-time registration and a dispute resolution. (FIG. 1, 110) Relative to document exchange 112, TPA 104 and TPB 106 can utilize the same application and can have a unique identity and unique login.

In an exemplary embodiment 200 and 250, FIGS. 2A and 2B illustrate a flowchart for a method of a document exchange and validation based on a non-repudiation protocol and a time-based one time password (TOTP) for encryption. The method comprises the following steps:

TPB 106 registers an application (App) with TTP 102 (step 202)

TTP 102 generates an initial “seed” based in part on a current time & sends initial “seed” to TPB 106 (step 204).

Steps 202 and 204 are only needed during one time registration.

TPA 104 sends a document to TPB 106. (step 206)

The user of TPB 106 reviews document (step 208)

Is the document acceptable to the user of TPB 106? (step 210). If yes, TPB 106 computes the current TOTP based on the current time and initial “seed” (step 213)

Subsequently, TPB 106 computes hash of the document using TOTP as encryption key. (step 214), and TPB 106 sends hash, current clock time, and GPS coordinates (may be optional) to TPA 104. (step 216)

If TPA 104 assumes that the current clock time and GPS coordinates (optional) of TPB 106 are within a threshold of the values for TPA 104, then TPA 104 stores the original document, hash, reported the hash was calculated, and the GPS coordinates (optional) (steps 217, 220).

If TPA 104 does not assumes that the current clock time and GPS coordinates (optional) of TPB 106 are within a threshold of the values for TPA 104, then TPA 104, then TPA 104 attempts to verify that TPB 106's current clock time and GPS coordinates (optional) are within a threshold of the values for TPA 104. (step 218)

If TPA 104 verifies that TPB 106's current clock time and GPS coordinates (optional) are within a threshold of the values for TPA 104, then TPA 104 stores the original document, hash, reported the hash was calculated, and the GPS coordinates (optional) (steps 218, 220)

If TPA 104 cannot verify that TPB 106's current clock time and GPS coordinates (optional) are within a threshold of the values for TPA 104, then TPA 104 sends a message to TPB 106, and TPB 106 proceeds to calibrate its device clock time. (step 224)

If after calibration, TPA 104 can verify that TPB 106's current clock time and GPS coordinates (optional) are within a threshold of the values for TPA 104, TPA 104 proceeds to store the original document, hash, reported the hash was calculated, and the GPS coordinates (optional) (steps 224, 220)

If after calibration, TPA 104 can not verify that TPB 106's current clock time and GPS coordinates (optional) are within a threshold of the values for TPA 104, the response from TPB 106 is rejected and the method ends. (step 222)

If the document is not acceptable in step 210, TPB 106 sends document to TPA 104 for correction. (step 212) The user of TPA 104 can modify the document using the computing device and regenerate the document to match the details of the actual event, e.g. the goods delivered.

The acceptability of a document is equivalent to a manual determination that the user of TPB 106 (e.g. first user) is ready to sign and accept a document. The user of TPB 106 verifies that the invoice states that all the products on the invoice were received by the user of TPB 106. The user of TPB 106 then proceeds and signs and accepts the document. That is, the entries in the document are correct and are acceptable to the user of TPB 106. For example: if the document is an invoice of the all the products that have been delivered by the user of TPA 104 to the user of TPB 106, then the user of TPB 106 verifies that fact before accepting the document.

In an exemplary embodiment 300, FIG. 3 illustrates a flowchart for a method of dispute resolution between two trading partners, such as the user of TPA 104 and the user of TPB 106. The method comprises the steps of:

The user of TPB 106 disputes reception or asserts document has subsequently been altered. (step 301)

TPA 104 transmits TPB 106's identity, original document, computed hash & hash's time to TTP 102. (step 302)

TTP 102 computes TOTP of TPB 106 at the reported time using “seed” for TPB 106. (step 304)

TTP 102 hashes supplied document with computed TOTP. (step 306)

TTP 102 compares computed hash to hash supplied by TPA 104 (originally from TPB 106). (step 308)

Are the hashes equal? (step 310) If yes, the document is legitimate. (step 312) If no, the document is not legitimate. (step 314)

In another exemplary embodiment, a method for a third party to verify a communication transmitted from a second device to a first device without the communication being transmitted via the third party comprises the steps of: (1) in response to receiving a registration request from the first device, sending a unique seed to the first device; and (2) in response to receiving a dispute request from the first device comprising a communication transmitted to the first device by the second device and a first hash and a time transmitted to the second device from the first device in response to the communication: (i) creating a time-based one time password (TOTP) using the time and unique seed (ii) creating a second hash of the communication using the TOTP; (iii) comparing the first and second hashes; and (iv) verifying the communication was received by the second device if the first and second hashed are equal. Additionally, transmitting, with the first device to the second device the GPS coordinates of the first device; and receiving, with the first device, a verification from the second device that the GPS coordinates of the first device are within a threshold of the second device's current GPS coordinates. Alternatively, receiving, with the first device, a rejection from the second device indicating that the GPS coordinates of the first device are not within a threshold of GPS coordinates of the second device. Additionally, the digital signature comprises one or more of the following: evidence, identify, document status, acknowledgement of informed consent by signer.

To supplement the present disclosure, this application incorporates entirely by reference the following commonly assigned patents, patent application publications, and patent applications:

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In the specification and/or figures, typical embodiments of the invention have been disclosed. The present invention is not limited to such exemplary embodiments. The use of the term “and/or” includes any and all combinations of one or more of the associated listed items. The figures are schematic representations and so are not necessarily drawn to scale. Unless otherwise noted, specific terms have been used in a generic and descriptive sense and not for purposes of limitation.

Claims

1. A method for a third party device to verify a communication transmitted from a second device to a first device without the communication being transmitted via the third party device, the method comprising the steps of: in response to receiving a registration request from the first device, sending, by the third party device, a unique seed to the first device;receiving, by the third party device, (i) a dispute request from the first device, the dispute request comprising the communication transmitted to the first device by the second device, (ii) a clock time of the first device when the first device transmitted the dispute request in response to the communication, and (iii) a first hash of the communication computed using a first time-based one time password (TOTP) that is created, by the first device, based on a current clock time of the first device and the unique seed; andin response to receiving the dispute request: creating, by the third party device, a second TOTP using the current clock time and the unique seed;creating, by the third party device, a second hash of the communication using the second TOTP;comparing, by the third party device, the first hash and the second hash; andverifying, by the third party device, the communication is received from the second device if the first hash and the second hash are equal.

2. The method according to claim 1, wherein: transmitting, by the first device, to the second device GPS coordinates of the first device; andreceiving, by the first device, a verification from the second device that the GPS coordinates of the first device are within a threshold of second device's current GPS coordinates.

3. The method according to claim 1, wherein: capabilities of the first device and the second device are equivalent, and the first device and the second device utilize the same application, andafter application registration neither the first device nor the second device access the third party device unless and until they have a dispute.

4. The method according to claim 1, wherein: if the first hash and the second hash are equal, transmitting, by the third party device, an indication to the first device and the second device that the communication provided by the second device is legitimate.

5. The method according to claim 1, wherein a digital signature is generated based on the first hash.

6. The method according to claim 5, wherein the digital signature comprises one or more of the following: an evidence of origin, an identity, a document status, an acknowledgement of informed consent by a signer.

7. The method according to claim 5, wherein the digital signature utilizes asymmetric cryptography.

8. The method according to claim 1, wherein the clock time of the first device is calibrated using a phone time/network time protocol.

9. The method according to claim 1, wherein the communication is acceptable when a first user manually determines an accuracy of content of a document associated with the communication.

10. A method of implementing a non-repudiation protocol, the method comprising: registering, by a first device, an application associated with the first device at a third party device, wherein the application registration is a one-time event;receiving, by the first device, a seed generated by the third party device based in part on a seed time;receiving, by the first device, a document from a second device;displaying, by the first device, the received document to a first user;in response to receiving a first input from the first user indicating acceptance of the document, performing: computing, by the first device, a first time-based one-time password based in part on a current clock time of the first device and the seed;computing, by the first device, a first hash of the document using the first time-based one-time password as an encryption key;transmitting, by the first device, to the second device the first hash and the current clock time when the first hash is computed by the first device, wherein the second device transmits the first hash and the current clock time to the third party device for computation of a second time-based one-time password; andreceiving an indication from the third party device indicating one of: the document is legitimate, wherein the third party device determines that the document is legitimate when the first hash is equal to a second hash of the document that is computed using the second time-based one-time password; andthe document is not legitimate, wherein the third party device determines that the document is not legitimate when the first hash is not equal to the second hash; andin response to receiving a second input from the first user indicating non-acceptance of the document: transmitting, by the first device, the document to the second device for correction.

11. The method according to claim 10, further comprising: transmitting, by the first device, to the second device GPS coordinates of the first device; andreceiving, by the first device, a rejection from the second device indicating that the GPS coordinates of the first device are not within a threshold of GPS coordinates of the second device.

12. The method according to claim 10, further comprising: in response to the second device determining that the current clock time of the first device is within a threshold of a current clock time of the second device, storing, by the second device, the first hash and the current clock time when the first hash is computed by the first device, andin response to the second device determining that the current clock time of the first device is not within the threshold of the current clock time of the second device, measuring, by the second device, to verify that the current clock time of the first device is within the threshold of the current clock time of the second device.

13. The method according to claim 12, further comprising, in response to the second device failing to verify that the current clock time of the first device is within the threshold of the current clock time of the second device, calibrating, by the first device, the current clock time of the first device.

14. The method according to claim 12, further comprising, in response to the current clock time of the first device not being within the threshold of the current clock time of the second device, receiving, by the first device, a rejection from the second device.

15. The method according to claim 10, further comprising: receiving, by the third party device, from the second device an indication of a dispute, an identity of the first device, the document, the first hash, and the current clock time when the first hash is computed by the first device;computing, by the third party device, the second time-based one-time password based in part on the received current clock time when the first hash is computed by the first device;computing, by the third party device, the second hash of the document with the second time-based one-time password;comparing the first hash to the second hash; andif the first hash and the second hash are equal, transmitting, by the third party device, an indication to the first device and the second device that the document provided by the second device is legitimate.

16. The method according to claim 10, further comprising: receiving, by the trusted third party device, from the first device an indication of a dispute, a second document asserted by the second device as legitimate, the first hash, and the current clock time when the first hash is computed by the first device;computing, by the third party device, the second time-based one-time password based in part on the received current clock time when the first hash is computed by the first device;computing, by the third party device, the second hash of the second document with the second time-based one-time password;comparing the first hash to the second hash; andif the first hash and the second hash are equal, transmitting, by the third party device, an indication to the first device and the second device that the document provided by the second device is legitimate.

17. The method according to claim 10, further comprising, generating a digital signature based on the first hash.

18. The method according to claim 10, wherein the document is acceptable when the first user manually determines an accuracy of content of the document.

19. A method of implementing a non-repudiation protocol, the method comprising: receiving, by a first device, a request for a document from a second device;transmitting, by the first device, the document to the second device;receiving, by the first device, a hash and a current clock time when the hash is computed by the second device, wherein the second device computes a time-based one-time password based in part on the current clock time and a seed that is received from a third party device, and wherein the second device computes the hash of the document using the time-based one-time password as an encryption key;verifying, by the first device, whether the current clock time of the second device is within a threshold of a current clock time of the first device;in response to verifying that the current clock time of the second device is within the threshold of the current clock time of the first device, storing, by the first device, the document, the hash, and the current clock time when the hash is computed by the second device; andin response to failing to verify that the current clock time of the second device is within the threshold of the current clock time of the first device, calibrating, by the second device, the current clock time of the second device.

20. The method according to claim 19, further comprising receiving, by the second device, a rejection from the first device, in response to the current clock time of the second device not being within the threshold of the current clock time of the first device, post calibration.