Methods and device for digitally signing data

TECHNICAL FIELD

The present invention relates, generally, to digital signatures of data and, more particularly, to methods and device for securely carrying out digital signatures of data in manner that can be used by non-technically skilled persons.

BACKGROUND OF THE INVENTION

There have many advances in the technology relating to the digital signature of documents. For example, standards such as the Public Key Infrastructure (PKI) have been established and widely accepted. As a result, Certification Authorities (CA) have been established and are increasing in number. Examples of public CAs are VeriSign, Thawte, and Entrust. CAs are used as a trusted third party to generate public-key certificates for an entity. Many entities use X.509 certificates, while other entities are using standards such as the public key cryptographic standard (PKCS) #7 for digitally sign soft documents.

Currently, many problems exist that inhibit the widespread acceptance of digital signatures. One problem is the lack of portability, from computer to computer, in present approaches used for digital signatures. The lack of portability often results in limiting a user of digital signatures to one specific computer.

Furthermore, there are many difficulties that arise when the recipient of a digitally signed document presents the document to a third party and attempts to establish to the third party, that the document was digitally signed by the original sender of the document. For example, the recipient may be able to verify that the received document has been signed, however, the recipient is unable to re-send the document to a third party, while keeping the original signature intact and valid.

Another problem is the lack of security in protecting private keys. Currently, digital signatures are computed using private keys. Public keys are associated with a particular entity, and are intended to be known to everyone who needs to have trusted interactions with that entity. The public keys are also used to verify signatures. Private keys must be protected from public access and are supposed to be known only to the particular entity that owns the private key. However, if private keys are not adequately protected, then they can be stolen by hackers. Hackers can steal private keys by hacking their way onto a computer and accessing the private keys that may be stored on the hard drive. Stolen private keys can be used to “forge” the digital signature of a particular entity. In addition, if the security of a private key is compromised, the signer of a specific document could deny ever signing the document, a fact that is referred to as “repudiation”, on the grounds that his key might have been stolen by a hacker and used to sign the document. Thus, private keys should be protected by adequate security mechanisms. However, adequate security mechanisms such as a “firewall” are expensive to install and maintain, and are often too complex for the typical individual user of a computer. Furthermore, it is well known in the art that even the best firewalls can be penetrated, and thus, even private keys protected by a firewall can be compromised and stolen by an unscrupulous hacker. These security issues have contributed to the lack of widespread use and acceptance of digital signatures.

In order to provide adequate protection for private keys, sophisticated technologies are required that are extremely expensive and may even require a network of personal computers. Clearly, these sophisticated solutions are not and never will be popular.

Other current solutions include storing private keys in chip cards or in USB tokens. These current solutions also have several disadvantages. For example, they require the use of special equipment to read the chip cards or they require the availability and accessibility of USB slots. In addition, it is worth noting that both chip cards and USB tokens, each of which require the physical connection of the chip card or USB token to a computer, could result in repudiation claims based on the scenario where chip cards or USB tokens can be actuated or triggered without the agreement and knowledge of the owner. The request of a fixed personal identification number (PIN) in order to actuate a chip card or USB token is not an obstacle for the unscrupulous hacker who can hack onto a computer and steal a PIN that has been previously entered into the computer.

In addition, many current solutions restrain the use of digital signatures to personal computers (PCs) or similar devices, and thus do not enable the sending of a digitally signed document through other types of devices such as a telephone.

An additional problem of present solutions lies in the CA/revocation list system which hands over to the recipient (13) the obligation to check the revocation list which is a concept that is not well known to a person who is not skilled in the art. Furthermore, a recipient (13) that checks the validity of the public-key certificate typically has to keep records that show that at a particular time the public-key certificate was not revoked, and, therefore, it was proper to accept the signature as verified. This further restricts the use of the digital signatures and prevents their widespread usage.

SUMMARY OF THE INVENTION

In accordance with one embodiment of the present invention, a method is disclosed that is designed for solving the problem of the mass usage of the digital signatures for soft documents. The method utilizes a system that includes a personal handheld device used by the user or “signer” of the soft document, as well as the use of a third party or entity (referred to as “Notarial Transaction Certification Server”) that may be represented by software executed on a central computer. The method starts with a soft document (referred to as the “Original File”, which can be any electronic file, e.g., a complete directory), that is to be signed by a specific entity (i.e., the signer), that may reside on a computerized device such as a personal computer (PC), a personal digital assistant (PDA) such as a Palm device, or any other type of computerized device (e.g., a cellular phone) that may store soft documents. The signer or “token holder” may use a personal handheld device (referred to as a “token”), such as the as the acoustic token disclosed in U.S. Pat. No. 6,236,724 (hereinafter referred to as the '724 patent) issued on May 22, 2001 and assigned to Encotone Ltd of Jerusalem, Israel. Alternatively, a cellular phone with special software or any other handheld or portable device, such as a PDA, may be used by the signer to carry out the methods of the present invention.

In accordance with the current embodiment of the present invention, the token holder applies a specific hash function (e.g., SHA1, MD5 or the like) to the original file that is to be signed. The hash computation may be carried out on the PC where the original file is stored. The application of the hash function to the original file produces a “Result.” Next, the token holder may enter the Result of the hash function into the token by means of the token's keypad or any other way such as by infrared communication, bar code scanner, optical means or the like. The Result may be stored in the token's memory. The stored Result may be referred to as “Locally Entered Data.” The token may encrypt the Locally Entered Data to produce “Cipher Text.” The encryption step may utilize well known encryption techniques such as RSA, DSA, or ECDSA. The token also computes a token's identification code, referred to as an “ID Code” or token's ID Code (7), that may be variable or dynamic. The ID Code and the Cipher Text may be encoded by the token, either separately or concatenated together, into sound waves or any other type of analog waves. The analog waves may be referred to as the “Acoustic Message.” The Acoustic Message may be transmitted to the PC which may receive the Acoustic Message, by means of a microphone or similar device. The PC may utilize a hardware or software module, referred to as a “Decoder”, that may be similar to the Decoder disclosed in the '724 patent, that records the Acoustic Message and decodes the Acoustic Message into digital digits. In this manner, the ID Code and the Cipher Text may be recovered and stored as a string of bits (referred to as a “Signature String”) in a computer-file or equivalent.

Next, the two files (i.e., the Original File and the Signature String) may be sent to a Recipient by means of the Internet, e-mail, modem, Intra-net, computer diskettes, CD-ROM or the like. The Recipient receives the two files and at the same time, or at a later time, may check or verify the digital signature of the Original File. The checking or verification process may be initiated by sending the Signature String File to a third party referred to as a Notarial Transaction Certification Server (NTCS). The NTCS may be embodied as software on a server that is connected to the Recipient by the Internet, wide area network, or any other connection.

The NTCS may interpret the ID Code received within the Signature String to determine the identity or serial number of the token that produced the ID Code. The NTCS may also determine the encryption key or public key that is necessary for decrypting the received Cipher Text such that the encrypted Locally Entered Data may be verified.

When the token's identity is established by the NTCS, the NTCS can prepare a document, such as a document in accordance with the PKCS#7 standard, which includes the identity of the token's owner and the Result of the Hash function as applied to the Original File. This document may be referred to as the Certificate of Integrity and Identity.

Next, the Certificate of Integrity and Identity (16) may be sent to the PC that transmitted the Original File. The token-holder may then store the Original File and its corresponding Certificate of Integrity and Identity for their records. In addition, the token holder may send the two documents to the Recipient using a variety of known techniques such as the Internet, e-mail, diskettes, or the like.

The Recipient can apply the same Hash function used by the token holder to the Original File. The Recipient can compare this “independently computed Result” with the Result received in the Certificate of Integrity and Identity (also referred to as Notarial Transaction Certificate).

If both Results are identical, then it may be inferred that the Original File received from the token holder has not been altered or tampered with. Furthermore, the Recipient may store for their records the Certificate of Integrity and Identity, which includes the ID of the token-holder, as a record of the identity of the person that digitally signed the Original File.

In accordance with another aspect of the present invention, a time stamp may be computed and included with the token's ID Code. The time stamp includes information as to the time at which the token holder digitally signed the Original File. The time stamp may be encrypted and included with the Signature String that is sent to the Recipient. The NTCS may then recover the time stamp and include it in the Certificate of Integrity and Identity. In this manner, the time at which the token holder digitally signed the Original File may be recorded in the Certificate of Integrity and Identity.

In accordance with another aspect of the present invention, a subset or part of the Result of the hash function may be used by the token holder as the Locally entered data. Similarly, the NTCS may receive the complete result directly, and the signed matching subset of the Result that is received within the Signature String. For example, the token holder may utilize 8 consecutive digits of the Result as Locally entered data, and the NTCS may verify such Locally entered data and match it with the complete Hash function result.

In accordance with another aspect of the present invention, a software application (referred to as the Signature Computation Application) may be used to execute the steps of applying a specific Hash function to the Original-File, displaying the total or partial Result of the Hash function, transmitting the total Result to the NTCS, open a time window for enabling the token-holder to prepare and send the Acoustic Message, decoding the Acoustic Message, creating the Signature String from the Acoustic Message, and transmitting the Signature String to the NTCS.

In accordance with another aspect of the present invention, the Recipient may utilize a software application (referred to as the Signature Verification Application) for executing the steps of opening the Certificate of Integrity and Identity, applying the Hash function to the Original-File, and comparing the independently computed Result with the Result received within the Certificate of Integrity and Identity.

In accordance with another aspect of the present invention, a Phone Gate server may be utilized. The Phone Gate server may comprise a computer server that may be accessed via a standard or wireless telephone connection. Once the token-holder has entered either the full or partial Hash function Result into the token, the token holder may place a call to the Phone Gate server by using a conventional or wireless telephone. Once the connection to the Phone Gate server is established, the token holder may use the telephone's microphone to send the Acoustic Message from the token to the Phone Gate Server. The Decoder software may execute on the Phone Gate Server and decode the Acoustic Message in order to recover the Signature String. Next, the Phone Gate Server may transmit the Signature String to the NTCS which may issue the Certificate of Integrity and Identity. In addition, the NTCS may store the Certificate of Integrity and Identity and/or send this Certificate to the signer or token holder. The token holder may now possess two documents—the Original File and the corresponding Certificate of Integrity and Identity. These documents may be stored by the token holder. In addition, the token holder may transmit the Original File and its corresponding Certificate to the Recipient. The Recipient may check and verify the documents by applying the Hash Function to the Original File and thereby obtaining an independently computed Result. The Recipient may next compare the independently computed Result with the Result stored in the Notarial Transaction Certificate (i.e., the Certificate of Integrity and Identity).

In accordance with another aspect of the present invention, a token is provided that includes the token owner's private key and installed software for enabling the token owner to digitally sign a data string (i.e., the locally entered data) which is keyed-in or otherwise entered into the token's memory. The token owner will apply a hash function to the data string and enter the Result (or a part thereof) into the token. The token will digitally sign the Locally Entered data (i.e., the entered Result) using the token owner's private key and thereby compute a digital string (the “Cipher text”). The token may then encode the cipher text and the token's ID Code into sound. The encoding into sound may be triggered by pressing a button on the token. The encoded sound (i.e., the Acoustic Message) may be transmitted to a Phone Gate server, after a connection has been made to the Phone Gate server, by pressing a button on the token. The Phone Gate server may convert the received Acoustic Message into a Signature String that may be transmitted to the NTCS. The NTCS may interpret the Signature String and determine the token's identity or serial number by utilizing the token's ID Code stored in the Signature String. In addition, the NTCS may retrieve the X.509 certificate corresponding to the token owner. The X.509 may be used by the NTCS to verify the received Cipher text and thereby verify the Locally entered data stored in the Signature String. Once the Locally entered data has been verified, the token owner ID may be extracted from the X.509 certificate and the NTCS may issue the corresponding Certificate of Integrity and Identity.

In accordance with another aspect of the present invention, cellular phones may be utilized instead of tokens. The cellular phone holder may enter the Locally entered data into the cellular phone. The cellular phone may have special software installed on it that may provide functionality for storing at least one private-key for encrypting strings, for example in the SIM card of the cellular phone, and the cellular phone may compute the digital signature of the entered data string.

In accordance with further aspects of the present invention, the cellular phone's batteries can be replaced with other special batteries, which includes all or most of the acoustic token components, and its functionality, and in this way the person who carries the cellular phone also carries the acoustic token capabilities and functionality.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

<figref idref="DRAWINGS">FIG. 1</figref> is a block diagram representing an exemplary system for performing the methods of the present invention;

<figref idref="DRAWINGS">FIG. 2</figref> is a block flow diagram that illustrates the flow of data for forming and decoding an exemplary digital signature for a document in accordance with an exemplary embodiment of the present invention;

<figref idref="DRAWINGS">FIG. 3</figref> is a block flow diagram that illustrates the flow of data for forming an exemplary certificate of identity and integrity for the identity of a digital signer of the exemplary digital signature of <figref idref="DRAWINGS">FIG. 2</figref> in accordance with an exemplary embodiment of the present invention;

<figref idref="DRAWINGS">FIG. 4</figref> is a block flow diagram that illustrates the flow of data for using the exemplary certificate of <figref idref="DRAWINGS">FIG. 3</figref> to check and verify the identity of the digital signer in accordance with an exemplary embodiment of the present invention; and

<figref idref="DRAWINGS">FIG. 5</figref> is a block diagram that illustrates an exemplary embodiment of the present invention.

DETAILED DESCRIPTION

The present invention may be described herein in terms of functional block components and processing steps. It should be appreciated that such functional blocks may be realized by any number of hardware or software components configured to perform the specified functions. For example, the present invention may employ various software components, e.g., logic elements, database tables, look-up tables, and the like, which may be used to carry out a variety of functions under the control of one or more microprocessors or other control devices. In addition, those skilled in the art will appreciate that the present invention may be realized in a software or computer program context in conjunction with any number of conventional computer system environments. Furthermore, the present invention is not limited to the process flows described herein, as any process flow or rearrangement of process steps which captures the features of the present invention is considered to be within the scope of the present invention. It should be noted that the present invention may employ any number of conventional techniques for processing steps such as database storing and retrieving, displaying text and graphics, printing output, sending files, and the like. Such general techniques that may be known to those skilled in the art are not described in detail herein.

It should be appreciated that the particular implementations and processes shown and described herein are illustrative of the present invention and its best mode and are not intended to otherwise limit the scope of the present invention in any way. Indeed, for the sake of brevity, conventional software programming and encryption techniques may not be described in detail herein.

As previously discussed, there is a need for a new method and system which will enable the secure digital signatures of documents. Referring now to <figref idref="DRAWINGS">FIG. 1</figref>, a system <b>100</b> for enabling digital signatures of documents comprises one or more personal handheld or portable devices <b>110</b> also referred to as tokens, and a third party <b>120</b>, also referred to as a Notarial Transaction Certification Server (NTCS). Users <b>115</b> of the tokens may use the tokens to digitally sign documents which may be transmitted to a recipient <b>130</b> who has a computer <b>135</b> or similar device for receiving computer documents.

The document to be signed may be referred to as the Original File <b>140</b> and may be stored on a computerized device, such as a personal computer <b>150</b>, a personal digital assistant (PDA) or the like. User <b>115</b> may use token <b>110</b>, which may be embodied by an acoustic token, such as the device disclosed in U.S. Pat. No. 6,236,724, (hereinafter the '724 patent) issued on May 22, 2001, to Encotone Ltd of Jerusalem, Israel, and herein incorporated by reference. Alternatively, user <b>115</b> may utilize a cellular phone with special software which will enable it to act in a similar manner to token <b>110</b> and which will be described in more detail below. Such a device may be embodied by such a device as disclosed in PCT patent application number PCT/IB/01989 and herein incorporated by reference or by any other handheld or portable device such as a PDA or token with acoustic capabilities, wherein all such devices may be referred to collectively as token <b>110</b>.

Computer <b>150</b> may further comprise a Decoder <b>155</b> that may be embodied as a software or hardware module to perform decoding functions as further described in detail below.

With reference to <figref idref="DRAWINGS">FIGS. 1 and 2</figref>, in accordance with one aspect of the present invention, token holder or user <b>115</b> utilizes computer <b>150</b> to apply a specific Hash function <b>205</b> (e.g., SHA1, MD5 or any other suitable hash function) to Original File <b>140</b>. The application of hash function <b>205</b> to original file <b>140</b> produces a result <b>210</b>. Next, user <b>115</b> may enter result <b>210</b> into token <b>110</b> by means of the token's keypad, by infrared communication, by scanning in a bar code, or by any other suitable means for entering data into token <b>110</b>. The entered data may be referred to as locally entered data <b>220</b> and in some cases, may be Hash result <b>210</b>. Token <b>110</b> may digitally sign the locally entered data <b>220</b> to produce cipher text or e-sign <b>230</b> which may include the Locally entered data <b>220</b> in a open way, not encrypted, on top of the encrypted or signed version. The encryption of locally entered data <b>220</b> by token <b>110</b> may be performed by applying a hash function to locally entered data <b>220</b> and then signing the hashed data by using digital signature standards such as the Elliptic Curve Digital Signature Algorithm (ECDSA), or other suitable asymmetrical algorithm, that utilizes a token specific private key <b>240</b>.

Next, token <b>110</b> computes a token identification code (ID Code) <b>250</b>. In accordance with one aspect of the present invention, the token ID Code may be a variable or dynamic code. Token <b>110</b> may encode ID Code <b>250</b> and cipher text <b>230</b>, either separately or concatenated together, into sound waves or any other type of analog waves to form acoustic message <b>260</b>.

Acoustic message <b>260</b> may be transmitted from token <b>110</b> to computer <b>150</b> by utilizing standard computer equipment such as a computer microphone and a sound card. Computer <b>150</b> may optionally store acoustic message <b>260</b>. Decoder <b>155</b> of computer <b>150</b> may decode acoustic message <b>260</b> to form signature string <b>270</b>. Signature string <b>270</b> may comprise a string of digits that correspond to token ID Code <b>250</b> and to cipher text <b>230</b>. It will be appreciated that signature string <b>270</b> may be embodied as a computer file or the equivalent. As described above, cipher text <b>230</b> includes locally entered data <b>220</b> which corresponds to result <b>210</b> of applying hash function <b>205</b> to original file <b>140</b>.

In accordance with one embodiment of the present invention, original file <b>140</b> and signature string <b>270</b> may be transmitted to recipient's computer <b>135</b> by Internet, e-mail, modem, Intra-net, computer diskettes, CD-ROM or the like. It will be appreciated that recipient <b>130</b> will have received two files—original file <b>140</b> and signature string <b>270</b>. In accordance with one aspect of the present, recipient <b>130</b> may check the identity of the digital signer of original file <b>140</b>, as well as the integrity of original file <b>140</b> in the following manner.

With reference to <figref idref="DRAWINGS">FIGS. 1 and 3</figref>, recipient <b>130</b> may transmit signature string <b>270</b> to a third party referred to as Notarial Transaction Certification Server (NTCS) <b>120</b>. NTCS <b>120</b> may comprise a computer server on the Internet or any other computer or similar device that may be in communication with recipient computer <b>135</b>. In addition, NTCS <b>120</b> is able to access X.509 repositories or the equivalent and retrieve X.509 certificates or the equivalent.

NTCS <b>120</b> interprets signature string <b>270</b> to determine the token's ID code <b>250</b> and cipher text <b>230</b>. As explained above, the NTCS may use the token ID Code <b>250</b> to determine the token serial number <b>310</b> that uniquely identifies the token that digitally signed the original file <b>140</b> as described below. The retrieval of the X.509 certificate may be made through the interpretation of ID code <b>250</b> to uniquely identify a token <b>110</b>. The retrieved X.509 certificate corresponds to token <b>110</b> that created the digital signature.

Since the token's ID code <b>250</b> has been interpreted by NTCS <b>120</b>, the specific token identity has been determined and hence, the corresponding X.509 can be retrieved from the X.509 certificate repository. The X.509 certificates or equivalent can be used to extract the pertinent public key and the identification data of the owner of the public key <b>320</b>. The NTCS <b>120</b> may determine the specific cryptographic key <b>320</b> (i.e., the Public Key included in an X.509 certificate that is associated with user or sending entity <b>115</b>). Public key <b>320</b> may be used to decrypt and verify the received cipher text <b>230</b> as will be described in detail next.

The verification of the signature string may be made by the use of the corresponding digital signature algorithm that was used to form the signature string (e.g., ECDSA), acting over locally entered data <b>220</b>, the signed version of the locally entered data, and the public key <b>320</b> extracted from the X.509.

Eventually, if the verification of cipher text <b>230</b> is successful, using the specific token owner <b>115</b> identity, NTCS <b>120</b> may prepare a Certificate of Integrity and Identity <b>330</b> that may be in the form of a computer document in accordance with known standards such as PKCS #7. Certificate <b>330</b> may comprise the identity of the token's owner and the verified locally entered data <b>220</b>, which in this embodiment is result <b>210</b> of applying hash function <b>205</b> to original file <b>140</b>. It will be appreciated that document <b>330</b> is a certificate, which ensures the integrity of the original file and the identification of the signer of the original file <b>140</b>.

In accordance with another embodiment of the present invention, user <b>115</b> may transmit signature string <b>270</b> directly to NTCS <b>120</b> and user <b>115</b> may receive certificate <b>330</b> from NTCS <b>120</b>. User <b>115</b> may then transmit original file <b>140</b> and certificate <b>330</b> to recipient <b>130</b>.

With reference to <figref idref="DRAWINGS">FIGS. 1 and 4</figref>, certificate <b>330</b>, also referred to as Notarial Transaction Certificate <b>330</b>, may be sent to recipient <b>130</b> in order to verify the integrity and identification of the signer of original file <b>140</b>. Recipient <b>130</b> can use computer <b>135</b> to apply the same hash function <b>205</b> to the presumed original file that was sent by user <b>115</b> to produce “independently computed hash result” <b>410</b>. Recipient <b>130</b> can also retrieve original hash result <b>210</b> from certificate <b>330</b> so that the original hash result <b>210</b> can be compared to the independently computer hash result <b>410</b>. If hash results <b>210</b> and <b>410</b> are identical, then it may be concluded that the presumed original file received from token-holder <b>115</b> is the correct original file <b>140</b> and has not been altered. Furthermore, recipient <b>130</b> now has the Certificate of Integrity and Identity <b>330</b> that is signed (e.g., using PKCS #7) by NTCS <b>120</b> wherein certificate <b>330</b> includes the token holder's ID and states that the token holder digitally signed the file that corresponds to the hash result that is included in certificate <b>330</b>.

It will be appreciated that if NTCS <b>120</b> is working within a Certification Authority (CA), then a totally user-friendly method for receiving a digitally signed file has been achieved, without the burden of asking the recipient to check the possible revocation of such certificate <b>330</b> that may be associated with the digitally signed file.

In accordance with another aspect of the present invention, a time stamp may be included that represents the time at which token holder <b>115</b> digitally signed original file <b>140</b>. The time stamp may be in the form of the Greenwich mean time (GMT) and date. The time stamp may be concatenated to token's ID code <b>250</b> and transmitted in acoustic message <b>260</b>. Consequently, the recovered signature string <b>270</b> may also include the time stamp which can be verified by NTCS <b>120</b>. Consequently, NTCS <b>120</b> may include the time stamp in the Certificate of Integrity and Identity <b>330</b> which represents the time at which the token holder <b>115</b> signed the original file <b>140</b>.

Referring back to <figref idref="DRAWINGS">FIGS. 1 and 2</figref>, in accordance with another aspect of the present invention, a signature computation application <b>112</b>, in the form of a software or hardware module, that may be stored in computer <b>150</b>, may be used by token holder <b>115</b> to compute the signature for original file <b>140</b>. Signature computation application <b>112</b> may be used to compute hash function result <b>210</b> of hash function <b>205</b> as applied to original file <b>140</b>. Signature computation application <b>112</b> may also be used to transmit hash result <b>210</b> to NTCS <b>120</b> via the Internet, preferably through a secure channel or an SSL communication link, or a standard or wireless computer or telephone connection. In addition, signature computation application <b>112</b> may transmit hash function result <b>210</b> to token <b>110</b> by any suitable method such as infrared communication, a bar code reader, optical reader, or, alternatively, by displaying result <b>210</b> or a part of result <b>210</b> using computer's <b>150</b> monitor such that token-holder <b>115</b> can key result <b>210</b> into token <b>110</b> by means of the token's keypad. As noted above, the entered data is referred to as locally entered data <b>220</b>.

In accordance with another aspect of the present invention, a part of hash result <b>210</b> may be used instead of the complete result. For example, eight consecutive digits of hash result <b>210</b> may be used or alternatively, any other strong function of hash result <b>210</b> such as parsing the result into any number of parts and xoring the parts (i.e., performing an XOR operation on the parts) to produce a new result that may be utilized by the token as locally entered data <b>220</b>. With continued reference to <figref idref="DRAWINGS">FIG. 2</figref>, token <b>110</b> now encrypts locally entered data <b>220</b> thereby e-signing the locally entered data as described above and producing cipher text <b>230</b>. Token <b>110</b> also computes the token's identification code <b>250</b> which may be concatenated with cipher text <b>230</b> (i.e., the signature string <b>270</b>) and encoded into acoustic message <b>260</b>.

Acoustic message <b>260</b> is transmitted by token <b>110</b> to computer <b>150</b> which receives the acoustic message by means of suitable equipment such as a microphone, a sound card, and the like. Signature computation application <b>112</b> may also include decoder <b>155</b> and thereby records acoustic message <b>260</b> and decodes the message into digital digits thereby recuperating token ID code <b>250</b> and cipher text <b>230</b>. As described above, a new file referred to as signature string <b>270</b> may be created which includes token ID code <b>250</b> and cipher text <b>230</b>. In accordance with this embodiment of the present invention, signature computation application <b>112</b> sends signature string <b>270</b> to NTCS <b>120</b> preferably through a secure channel or an SSL communication link.

Next, with reference to <figref idref="DRAWINGS">FIG. 3</figref>, NTCS <b>120</b> interprets the token ID code <b>250</b> received within signature string <b>270</b> thereby determining the token identity (i.e., the token serial number <b>310</b>). In accordance with another aspect of the present invention, NTCS may use a X.509 repository. After the interpretation of the token ID code to produce the token serial number <b>310</b>, NTCS <b>120</b> may retrieve the corresponding X.509 certificate thereby produce the token holder identity and the public key <b>320</b>. Using public key <b>320</b>, NTCS <b>120</b> may verify the digital signature on the locally entered data <b>220</b>. If successful, the veracity of the locally entered data as well as the identity of signer <b>115</b> may be confirmed.

For the specific case where the locally entered data <b>220</b> contains a partial result (e.g., a function of the result <b>210</b>), NTCS <b>120</b> compares and matches the partial result with all of the results that have been received from NTCS <b>120</b> during a pre established window of time, and when a successful match is made, then the relevant result <b>210</b> for this transaction has been determined.

In all cases, with reference to <figref idref="DRAWINGS">FIG. 3</figref>, once the corresponding result <b>210</b> and the token owner's <b>115</b> identity is established, NTCS <b>120</b> can prepare a certificate of integrity and identity <b>330</b>, which may be in the form of a PKCS #7 document, and which includes the identity of the token's owner <b>115</b> as well as the original file's hash function result <b>210</b>, all signed by the NTCS <b>120</b>, which may be a CA. Certificate <b>330</b> may now be transmitted to computer <b>150</b> of token holder <b>115</b>. Signature computation application <b>112</b> receives certificate <b>330</b> and opens the certificate and verifies the NTCS signature (path, revocation list) proceeding according to the standards for digital signature verification, and, if valid, extracts from the certificate of integrity and identity, the hash result <b>210</b>. Next, signature computation application <b>112</b> computes, independently, the hash function result of original file <b>140</b> referred to as independent result <b>410</b>. Result <b>410</b> is now compared to result <b>210</b> extracted from the certificate of integrity and identity <b>330</b>. If results <b>410</b> and <b>210</b> are identical, signature computation application <b>112</b> may announce to token holder <b>115</b> that a valid certificate <b>330</b> corresponding to original file <b>140</b> has been received. Otherwise, token holder <b>115</b> may destroy the received certificate of integrity and identity <b>330</b>.

The token holder <b>115</b> can now store both documents—that is original file <b>140</b> and certificate of integrity and identity <b>330</b> as a record keeping procedure for future usage, or, alternatively, can transfer both documents using any media (e-mail, CD-ROM) to one or more recipients <b>130</b>.

Now recipient <b>130</b> receives the two files <b>140</b> and <b>330</b> wherein we will momentarily refer to the received original file <b>140</b> as the presumed original file due to the fact that the original file may have been replaced or modified by an unscrupulous hacker.

At any time, recipient <b>130</b> may check the integrity and identity of the author of the presumed original file. Initially, recipient <b>130</b> may open the received PKCS#7 certificate of integrity and identity <b>330</b> and verify the NTCS signature (path, revocation list) using standard tools such as Microsoft Outlook Express or other suitable tool. If the certificate of integrity and identity was digitally signed by the NTCS, recipient <b>130</b> may extract from such certificate the hash result <b>210</b>. Next, recipient can independently compute the hash function result of the presumed original file to produce hash result <b>410</b>. Hash results <b>210</b> and <b>410</b> are compared, and if the results are identical, the recipient will have verified the integrity of the presumed original file. The verification of the presumed original file will imply that the presumed original file is identical to original file <b>140</b> referred to in the certificate of integrity and identity <b>330</b> and consequently, the author or signer of such document is the one appearing in the certificate of integrity and identity.

Furthermore, recipient <b>130</b> now has possession of the certificate of integrity and identity <b>330</b> that is signed in accordance with PKCS #7 by NTCS <b>120</b>, and includes the ID of the token holder <b>115</b> implying that token holder digitally signed the document corresponding to hash function result <b>210</b> and, therefore the received document matches the original file <b>140</b>.

In accordance with another aspect of the present invention, a method as disclosed above is presented wherein NTCS <b>120</b> is run by a Certification Authority (CA) which is an entity trusted by the community and legally recognized as a trustee for the issuance of digital certificates.

In accordance with further aspects of the present invention, tokens <b>110</b> are used such as the devices disclosed in U.S. Pat. No. 5,524,072 herein incorporated by reference. In addition, the token ID computation may use the methods disclosed in PCT application number PCT/IB98/01834, herein incorporated by reference.

In addition, with reference to <figref idref="DRAWINGS">FIG. 1</figref>, many of the above described implementations can be complemented by providing recipient <b>130</b> with a software or hardware module <b>138</b> which can execute in the recipient's computer <b>135</b>. Module <b>138</b>, referred to as the signature verification application, executes the steps of verifying and opening the certificate of integrity and identity <b>330</b>. and thereby recovering the hash function result <b>210</b>. In addition, application <b>138</b> applies the hash function <b>205</b> onto the received and presumed original file and compares the independently computed result <b>410</b> with the result <b>210</b> received within the certificate of integrity and identity <b>330</b> as described above.

With reference to <figref idref="DRAWINGS">FIG. 5</figref>, in accordance with a further aspect of the present invention, is a system that includes the features already disclosed and further includes a phone gate server <b>510</b>. As already disclosed, token holder <b>115</b> enters or keys in the full or partial hash function result into token <b>110</b>. Next, token holder <b>115</b> places a call, utilizing any standard or wireless telephone, to phone gate server <b>510</b> which comprises a computer server that may be connected by a standard or wireless telephone connection to the Internet or a suitable local area network (LAN). Next, by placing token <b>110</b> proximate to the telephone microphone, acoustic message <b>260</b> may be transmitted to phone gate server <b>510</b>. Decoder software <b>155</b> may be executed on the phone gate server <b>510</b> such that decoder <b>155</b> will decode acoustic message <b>260</b>, and thereby recuperate the token ID Code <b>250</b>, the time stamp, if present, and cipher text <b>230</b>, and thereby create the signature string <b>270</b> as previously described.

Next, phone gate server <b>510</b> may send signature string <b>270</b> to NTCS <b>120</b>, which has previously received result <b>210</b> from the signature computation application <b>112</b>. As a result, NTCS <b>120</b> can compute the certificate of integrity and identity <b>330</b> as previously disclosed and send it to the token holder PC <b>150</b>, and the process may continue as previously described.

For example, phone gate server <b>510</b> may send signature string <b>270</b> to NTCS <b>120</b> thereby enabling the NTCS to compute the certificate of integrity and identity <b>330</b>. However, NTCS <b>120</b> may now send to the token holder's computer <b>150</b> the certificate of integrity and identity <b>330</b>. Next, token holder <b>115</b> may send original file <b>140</b> and certificate <b>330</b> to recipient <b>130</b>. Whenever recipient <b>130</b> desires to check and verify the presumed original file, recipient <b>130</b> may apply hash function <b>205</b> to the received original file and thereby obtain independently computed result <b>410</b>.

Next, recipient <b>130</b> can verify the received certificate of integrity and identity and read hash function result <b>210</b>. Recipient <b>130</b> may compare the independently computed result <b>410</b> to hash result <b>210</b> for identity, as explained above.

A possible variation of the method is as above but before sending the certificate of integrity and identity, NTCS <b>120</b> may send only hash result <b>210</b> through a secure channel such as a secure socket link (SSL) or other suitable secure channel. Signature computation application <b>112</b> executing on computer <b>150</b> may re-check or verify the validity of the digital signature operation by re-computing the hash result of the original file and comparing the result with the original hash result <b>210</b> that was received. If there is a match, then application <b>112</b> may signal NTCS <b>120</b> to send certificate <b>330</b>.

As a variation of the method previously described, token holder <b>115</b> can send the original file to the Recipient <b>130</b>. Recipient can apply hash function <b>205</b> to the presumed original file and obtain independently computed hash result <b>410</b>. Next, recipient <b>130</b> can check and verify the presumed original file by contacting or approaching the NTCS <b>120</b> and requesting a certificate authored by the sender or token holder <b>115</b>, providing details such as the independently computed hash result <b>410</b> in order for NTCS <b>120</b> to be able to track the relevant stored certificate <b>330</b>. NTCS <b>120</b> will send the appropriate certificate of integrity and identity <b>330</b> to the recipient <b>130</b> and the recipient can proceed with checking the received certificate of integrity and identity <b>330</b> as described above.

In accordance with another aspect of the present invention, the methods of the present invention may include compatibility with the previously mentioned PKI standards wherein the token owner's private key <b>240</b> is generated in token <b>110</b>, according to one of the standard asymmetrical algorithms such as the RSA, ECDSA and the like, and the private key <b>240</b> is then stored on the token <b>110</b>. In addition, software for enabling the digital signature of a string such as locally entered data <b>220</b> has already been installed onto token <b>110</b>. In this manner, token holder <b>115</b> may enter all or part of hash function result <b>210</b> or any other data into token <b>110</b>. Token <b>110</b> may then hash such entered locally entered data <b>220</b>, and digitally sign it using the private key and thereby computing a digital string referred to as cipher text <b>230</b>, which may include the locally entered data <b>220</b> as open data.

In accordance with one aspect of the present invention, the locally entered data <b>220</b> may be digitally signed by hashing such data <b>220</b> and then using the private key to sign the hashed data following one of the known standards (e.g., ECDSA), and then concatenating the data <b>220</b> in an open way. Next, token <b>110</b> may concatenate a token ID code <b>250</b> to the cipher text <b>230</b> as previously disclosed and encode the result into sound waves and produce acoustic message <b>260</b>. The data flow is similar to the examples mentioned above, except NTCS <b>120</b> may now query an X.509 repository and retrieve the specific X.509 certificate, that has been issued by a recognized certification authority (CA), that corresponds to token owner <b>115</b> and thereby extract the relevant public key <b>320</b> as well as the signer identity.

With reference to <figref idref="DRAWINGS">FIG. 3</figref>, the signature computation application <b>112</b> or the phone gate server may record and decode the acoustic message by means of a specific software module referred to as a decoder <b>155</b>. NTCS <b>120</b> may interpret the received token ID code <b>250</b> and determine the token serial number <b>310</b> and thereby retrieve the appropriate X.509 certificate of the token owner <b>115</b>. Using the certificate, the token owner identity and the token public key <b>320</b> may be determined.

In accordance with another aspect of the present invention, token <b>110</b> may computes a totally dynamic ID code <b>250</b> based on a reversible algorithm and wherein NTCS <b>120</b> has the key or keys to reverse the algorithm and retrieve the token identification <b>250</b>. In this manner, an eavesdropper will be unable to easily identify or track the token holder <b>115</b>.

In accordance with another aspect of the present invention, the ID code <b>250</b> may include the GMT time and date stamp, in order to state the time of the transaction and avoid repeated use of the same acoustic message <b>260</b>.

In accordance with further aspects of the present invention, a solution of the problem of the Card-Not-Present Credit Card transactions is enabled. As it is well known in the art, remote transactions utilizing credit cards fall in the category of Card-Not-Present Credit Card (CC) transactions wherein the credit card holder cannot conventionally sign a document as proof of their acceptance of the transaction (i.e., to charge the credit card holder's credit card account for the transaction).

In accordance with another aspect of the present invention, the credit card holders may send to their credit card issuer, a PKI signed, transaction specific Certificate, by means of token <b>110</b>, through computer <b>150</b> or through a standard or cellular telephone. The credit card issuer may deliver to the credit card holder an acoustic token, or the acoustic token may be in the hands of the Credit card holder due to other reasons (e.g., corporate's network access) wherein the Credit Card Account is limited in its capacity to complete remote transactions or Card-Not-Present Credit Card transactions when there is not a PKI signed transaction Certificate specific for such a transaction, that is digitally signed by the card holder.

When the credit card holder decides to complete an e-commerce, telephone, or internet transaction (e.g., buying a book from an internet or remote merchant), the credit card holder may enter into their token, locally entered data <b>220</b> which includes the amount to charge to the credit card.

As explained above, the token may compute a digital signature of the locally entered data <b>220</b> which, may be concatenated with the GMT time and date, and thereby create a signature string <b>270</b>. Signature string <b>270</b> may includes an ID-Code (<b>250</b>) which may be the token serial number <b>310</b>. In addition, the signature string <b>270</b> may include the locally entered data <b>220</b>, the GMT time and Date, the locally entered data, the GMT time and Date, wherein the locally entered data and the GMT time and date may be digitally signed (i.e., encrypted with the token's private key <b>240</b> according to the ECDSA). The token will also encode the signature string <b>270</b> to sound and thereby produce an acoustic message <b>260</b>.

In accordance with another embodiment of the present invention, the token holder calls the credit card issuer and sends the acoustic message through the phone (standard or wireless) to the credit card issuer. As explained above, by means of the phone gate server <b>510</b>, the acoustic message <b>260</b> is converted into a signature string <b>270</b> and transmitted to a NTCS <b>120</b>, which, as explained before, verifies the signature. In this case, the NTCS interprets the received token's ID code <b>250</b> that is stored within the signature string <b>270</b> and thereby determines the token identity (i.e., the token serial number <b>310</b>). Next, the NTCS <b>120</b> can obtain the tokens owner's identity by querying a X.509 repository. Utilizing the token serial number <b>310</b>, the NTCS can retrieve the corresponding X.509 certificate and extract the token holder identity as well as the Public Key.

Next, the NTCS <b>120</b> may verify the digital signature of the locally entered data <b>220</b> and the GMT time and date if present. If the verification is successful, NTCS <b>120</b> may issue a verification certification (e.g., in accordance with PKCS #7) with the token holder <b>115</b> identity and the verified locally entered data <b>220</b> which includes the transaction amount. Once the credit card holder completes the credit card transaction procedure (i.e., sends back to the merchant the form), the merchant will request the credit card transaction authorization as usual. It should be appreciated that the present method is totally transparent to the merchant.

When the transaction authorization request arrives at the credit card issuer, the issuer will check if the credit card holder has sent the PKI Signed transaction authorization (i.e., for the exact amount). If the authorization has been received, the credit card issuer will go ahead with the transaction authorization procedure, otherwise, it will stop it.

As a variation of this method for credit card issuers, instead of using the phone to send the acoustic message, the credit card holder may send the same acoustic message <b>260</b> to the computer <b>150</b> microphone, wherein a software module which includes a decoder <b>155</b> will decode the acoustic message <b>260</b> into a signature string <b>270</b> and send the signature string to the credit card issuer's NTCS <b>120</b>.

It is hereby suggested that the above presented Credit Card Issuer solution may complement the Visa's 3D Secure methodology, in regard to achieve cardholder's digital signature for the specific transaction authorization.

In accordance to another aspect of the present invention, token <b>110</b> generates a signature string <b>270</b> and encodes the signature string to sound <b>260</b> (i.e., the acoustic message). The acoustic message <b>260</b> may be transmitted to computer <b>150</b> and decoder <b>155</b> may then decode the acoustic message into signature string <b>270</b>. The signature string <b>270</b>, or a portion of the signature string that includes ID code <b>250</b>, may be transmitted to a third party entity <b>120</b>. The third party entity may then retrieve the corresponding X.509 certificate and send the certificate to computer <b>150</b>.

In accordance with further aspects of the present invention, instead of using computer <b>150</b>, the acoustic message <b>260</b> may be sent through a conventional or wireless telephone to a telephone gate <b>510</b>. Telephone gate <b>510</b> may then decode the acoustic message into signature string <b>270</b> and send the digital string <b>270</b>, or a portion of digital string <b>270</b> that includes ID code <b>250</b>, to third party entity <b>120</b>. The third party entity may then retrieve the corresponding X.509 certificate and send the certificate to computer <b>150</b>.

According to a further implementation, the acoustic token may be a cellular phone, and the token holder enters the locally entered data as in any of the cases above, into the cellular phone instead of into the token. The cellular phone also includes installed software wherein the software enables the storing of at least one private key for signing strings, and the other functions of the token as previously described, including the capability to compute ID codes, digital signatures and to generate as sound the acoustic message <b>260</b>.

In addition, according to another aspect of the present invention, the cellular holder places a call, by means of the cellular phone, to a specially configured computer server, referred to as a certificate storing server, which is a server which stores for each of the cellular phone's holders, the corresponding X.509 certificate issued to the cellular-holder. In addition, the certificate storing server identifies the cellular phone by means of the caller-ID method or by other suitable means. During the call, the cellular-phone sends as digital data (e.g., SMS) or acoustic data, the signed version of the previously entered locally entered data <b>220</b>, referred to as cipher text <b>230</b>, wherein the certificate storing server verifies, keeps, and stores the cipher text. In addition, whenever the recipient <b>130</b> would like to check and verify the received presumed original file <b>140</b>, the recipient contacts the certificate storing server, and sends data in order to enable the certificate storing server to retrieve the relevant cipher text <b>230</b> and the corresponding X.509 certificate. Data that can be used to track the corresponding cipher text <b>230</b> can be, for example, the independently computed Hash Result <b>410</b>. Once the retrieving process is completed, the certificate storing server sends to the recipient <b>130</b> the cipher text <b>230</b> as well as the corresponding X.509 certificate.

In accordance with another aspect of the present invention, the secret key <b>240</b> and special software with the functions of the acoustic token may be inserted into the cellular phone by means of the cellular phone SIM card. Alternatively, the special software may be inserted into the CPU of the cellular phone and just the secrets keys (i.e., private key) will be in the SIM Card.

One configuration is to replace the cell phone battery with a special battery containing totally or partially the acoustic token hardware and software components, and also other components, in order to enable-phone holders, any type of present in use phones, to carry only the cellular phone wherein the cellular phone contains the acoustic token capabilities.

In accordance with another aspect of the present invention, the method further comprises a strong authentication method wherein an authentication server is installed in a network to be accessed, in order to authenticate the entities trying to access the network locally or remotely, and wherein the authentication server generates a challenge and sends this challenge to the entity (i.e., a token holder network accessor) which is attempting to access the network, and wherein the token holder digitally signs the challenge by means of the acoustic token entering the challenge as locally entered data <b>220</b>, and wherein the corresponding signature string <b>270</b> is sent back to the authentication server. According to the current method of the present invention, the authentication server by means of the token serial number will know who the accessor pretends to be, and may retrieve the corresponding X.509, and thereby verify the signature of the challenge, and eventually, if confirmed, to check the authorization of the accessor, which is the token owner as it appears in the X.509 certificate.

A variation of this method is, as above, but wherein the methods are applied to physical access to physical areas, like buildings, rooms, restricted areas, and wherein the authentication server sends a challenge, and the accessor by means of the token, responds with a response, which is the challenge digitally signed as above.

An additional variation of this method is, as above, but, instead of signing a challenge, as locally entered data <b>220</b>, the token holder does not enter any data at all. This time, the token will compute an ID Code <b>250</b>, and will digitally sign the ID code <b>250</b>. Now, the method is as above, but instead of the locally entered data <b>220</b>, there is ID-code <b>250</b>, which optionally has the time stamp embedded.

Another variation of the device and method of the present invention is a token with keypad and display which has a detachable part with a USB connector, and wherein the token holder as in all the cases above, enters locally entered data <b>220</b> in the token while the detachable part with the USB connector is attached. After data <b>220</b> is entered, the token holder may detach the detachable part in order to carry the signature string <b>270</b> to a USB compatible device (e.g., a PC), instead of using acoustical capabilities to transmit the signature string <b>270</b>.

Also, the detachable part may be used to carry the locally entered data <b>220</b> into the token in the following way: assuming an original file <b>140</b> is in PC <b>150</b> and the Hash result <b>210</b> is computed, i.e.: when the detachable part is connected by means of the USB connectivity means of the PC <b>150</b>. Now the Complete hash <b>210</b> is transmitted or burned into the detachable part. If the detachable part is now detached and attached to the token, the token will proceed as above, when in this case the locally entered data <b>220</b> will be the data previously burned into the detachable part.

A further variation of the method of the present invention is an acoustic token as above, which on top of the functions described above computes, at one particular instance, the private key <b>240</b> and the corresponding public key <b>320</b>, and, at one particular instance generates as sound the public key <b>320</b>, for the purpose of enrollment and generation of the X.509 certificate.

A further configuration is as above but after the enrollment, the token receives, through optical means, or other media, a king of simplified X.509 certificate, mainly with the private key <b>320</b> and the owner's ID data, signed by a CA, in a way such, when the token is used for signing locally entered data <b>220</b>, it will concatenate to the signature string <b>270</b>, such simplified X.509 certificate issued by a known CA and previously burned into the token.

In this way, the token will encode to sound the signature string <b>270</b> and the simplified X.509.

Although the invention has been described herein in conjunction with the explanation and examples mentioned above, those skilled in the art will appreciate that the scope of the invention is not so limited. Various modifications in the selection and arrangement of the various components and method steps discussed herein may be made without departing from the spirit of the invention as set forth in the appended claims.