HK1105794A

HK1105794A - System and method for implementing digital signature using one time private keys

Info

Publication number: HK1105794A
Application number: HK07114175.1A
Authority: HK
Inventors: 陈德源
Original assignee: 数码安信有限公司
Priority date: 2004-07-23
Filing date: 2005-07-11
Publication date: 2008-02-22

Abstract

The present invention relates to a system and method for implementing digital signatures using one time private keys. A system (5) implements digital signatures over a network and comprises a signing entity (20), a secure server (30), an OTPK (One Time Private Key) module (40) and an authentication server (50). The signing entity (20), the secure server (30), the OTPK module (40) and the authetication and certification server (50) are able to communicate with each other through established protocols of secure communications. The OTPK module (40) performs the function of generating only new asymmetric key pairs and also performs the functions of generating digital signatures or digitally signing the transactions. The transactions or instructions are authorised by way of a digital signature and once the digital signature has been generated using a private key, this private key is irretrievably deleted and the deleted private key can no longer be re-used).

Description

System and method for performing digital signatures using one-time private keys

Technical Field

The present invention relates to digital signatures using asymmetric keys, and more particularly, to a system and method for performing digital signatures using a one-time private key.

Background

Digital signatures for verifying and authorizing transactions, documents, contracts, directives, and others on the internet are more widely used as legislative legislation is being accepted for its use at the global level. Part of this law includes guidelines on security and authentication to ensure the legitimacy of digital signatures.

Invariably, the use of PKI (Public Key Infrastructure) is recognized in this law. When considering PKI for digital signatures, all entities involved in the transaction rely on a trusted third party to perform the necessary authentication of the identity and trustworthiness of the entity. This trusted third party is known as a CA (Certification Authority).

The CA issues to each entity a certificate that includes information such as the entity's name, country of origin, policies governing the use of the digital certificate, and most importantly, the entity's public key.

The digital certificate from the CA asserts that the entity described in the digital certificate is legitimate and is the only owner of the private key corresponding to the public key.

When a transaction requires a digital signature to be signed, the signing entity uses its private key to digitally sign the transaction. The entity receiving the signed transaction will also receive the signing entity's digital certificate. By using the public key in the digital certificate, the receiving entity can verify that the transaction has been digitally signed by the correct party, i.e., the signing entity. The operation of PKI and its applications and limitations are well known and will not be discussed further.

One limitation imposed by the law in ensuring secure use of PKI is that the law requires that the private key of the signing entity is always and only owned by the signing entity. This attempts to ensure that no other party can obtain a digital signature that uses the signing entity's private key to represent him improperly.

Currently, there are several methods of ensuring possession of a private key and preventing theft and loss of the private key.

In one of the prior art methods, a smart card is used. The private key is electronically stored in a memory device of the smart card. The smart card reader is then required to read the data from the smart card. To further ensure secrecy, the password must be entered into a computer connected to the smart card to allow the private key from the smart card to be used to perform the cryptographic operation. However, this method is expensive and cumbersome to implement because of the physical smart card and card reader required. In case the smart card is lost, a new smart card has to be issued to the user, while the private key of the old smart card has to be invalidated.

Microsoft CSP (Cryptographic Service Provider) provides an alternative to smart cards. The microsoft CSP is implemented as a software token that operates like a smart card and performs the function of digitally signing transactions. The microsoft CSP is also used by password. However, the main concern is that the private key is stored on the hard disk of a computer with installed microsoft CSP. Disadvantageously, the private key is open to computer viruses and attacks by hackers attempting to copy the private key.

Another prior art implementation is the key Web cryptographic scheme of RSA security corporation. This is a "virtual" smart card solution that relies on a back-end server to securely store the private key. When the user needs to use the private key, the private key is downloaded from the back-end server to be used by the user. Although this scheme is considered somewhat more secure than the CSP implementation, there is a debate as to whether the private key is "always" owned by the user.

Accordingly, there is a need for an improved system and method for performing digital signatures over a network that overcomes, or at least mitigates, the disadvantages of prior art systems.

Disclosure of Invention

The present invention seeks to provide a system and method for performing digital signatures using a one-time private key.

Accordingly, in one aspect, the present embodiments provide a method for completing a transaction from a signing entity to a receiving entity over a network using a digital signature, the method comprising the steps of:

a) instructions provided to the receiving entity for completing the transaction;

b) digitally signing the transaction by a digital signature generated using a private key; and

c) the private key is irretrievably deleted.

Wherein the private key is used only once to generate a digital signature; further wherein the private key never leaves all of the signing entity.

Thus, in a second aspect, the present embodiments provide a computer-executable method of completing a transaction from a signing entity over a network to a receiving entity using a digital signature, the method comprising the steps of:

a) generating a new asymmetric key pair comprising a private key and a public key;

b) generating a certificate request comprising a public key;

c) generating a digital signature using a private key; and

d) the private key is irretrievably deleted.

Accordingly, in a third aspect, the present embodiments provide a system for completing transactions over a network using digital signatures, comprising:

a signing entity wishing to complete a transaction with a receiving entity over a network;

an OTPK (One-time Private Key) module built into the signing entity, which is only used to generate a new asymmetric Key pair comprising One public Key and One Private Key, the OTPK module generating a digital signature using the Private Key and generating a certificate request containing the public Key;

a certification and certification server for certifying the identity of the signing entity, for receiving a certificate request, and for issuing a digital certificate for the public key ownership attested by the signing entity;

Thus, in a fourth aspect, the present embodiments provide a computer-executable method for completing a transaction between a signing entity and a receiving entity over a network using a digital signature at a new initial stage using a one-time private key (OTPK) module, the method comprising the steps of:

a) generating includes based on a notification that a secure transaction requiring a digital signature is desired

A new asymmetric key pair of a private key and a public key;

b) generating a certificate request comprising a public key;

c) generating at least one digital signature using a private key; and

d) the private key is irretrievably deleted.

Wherein the private key is used to generate a digital signature only when a new initial phase is activated; further wherein the private key never leaves all of the signing entity.

Drawings

Embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, in which:

FIG. 1 is a block diagram of a system for performing transactions over a network using digital signatures in accordance with the present invention;

FIG. 2 is a flow diagram of a method of performing digital signatures in accordance with the present invention;

FIG. 3 is a flow diagram of authorizing the transaction of FIG. 2.

Detailed Description

In the following description, details are provided to describe preferred embodiments of the present invention. It will be apparent, however, to one skilled in the art that the embodiments may be practiced without these specific details. Some of these details may not be described in detail in order to avoid obscuring the preferred embodiments.

Referring to fig. 1, a system 5 for performing digital signatures over a network is shown comprising: a signing entity 20, a secure server 30, an OTPK (one time private key) module 40 and an authentication and certification server 50.

In this example, the network is the internet 10. The signing entity 20, the secure server 30, the OTPK module 40 and the authentication and certification server 50 are able to communicate with each other through an established secure communication protocol.

The signing entity 20 in this embodiment is embodied as a computer of an entity wishing to perform a transaction over the internet 10 that requires the use of a digital signature to accompany or authorize the transaction. The secure server 30 may be a service provider or financial institution that receives instructions from the signing entity 20 to perform certain services or to facilitate the transaction of money. The security server 30 may alternatively refer to the receiving entity.

The signing entity 20, which is typically considered a computer such as a PC or apple computer, may also be any device that can be used for communication. Some examples are wireless communication devices such as mobile phones, PDAs and notebooks with WI-FI. Likewise, the network may further include wired and wireless networks employing any of the communication protocols established for data transmission, particularly for transactions.

The authentication and certification server 50 can be easily referred to as a current certificate authority for using PKI. Although the authentication and certification portions may be accomplished by different servers, the authentication and certification server 50 is considered a single entity in this example. The authentication and certification server 50 may also be internal to the security server 30 or receiving entity and may not necessarily be an external party.

The OTPK module 40 can be considered a software module built into the signing entity 20. The OTPK module 40 performs the function of generating only new asymmetric key pairs, and also performs the function of generating digital signatures or digitally signing transactions. The OTPK module 40 performs its functions automatically without further intervention or instruction from the signing entity 20 or the user.

Referring to fig. 1 and 2, when the signing entity 20 wishes to perform a transaction accompanied by a digital signature through a service provider having either the secure server 30 or the receiving entity, a method 200 of completing a transaction using a digital signature begins with the step 210 of the signing entity 20 providing instructions to the secure server 30 to perform a secure transaction. The instructions to secure server 30 may include information about the transaction of the money, or may also include instructions or requests for services or goods.

The next step 215 is to perform a transaction that authorizes the transaction, or the transaction contained in the instruction, using the digital signature. The transaction or instruction is authorized by a digital signature. The secure server 30 or receiving entity will be able to verify the digital signature.

Next, a step 220 of irretrievably deleting the private key used to generate the digital signature is performed. Once the private key is irretrievably deleted, the deleted private key cannot be reused, the private key cannot be stolen, and cannot be abused by an unauthorized party.

Referring to fig. 3, step 215 authorizes the transaction or provides instructions to the secure server, further starting with the OTPK module 40 generating a new asymmetric key pair comprising a private key and a public key.

Next, a step 315 of generating a digital signature using the private key is performed. Alternatively, the private key may be used to digitally sign transactions that are sent to the secure server 30.

Next, 320 generates a certificate request containing the public key. The certificate request is then sent 325 to the authentication and certification server 50 where the identity of the signing entity 20 is authenticated and a digital certificate is issued to prove ownership of the public key. The digital certificate may be in the form of x.509 and may further contain certain scopes and policies that in this embodiment are valid for use only once.

The digital certificate from the authentication and certification server 50 is then received 330 for the signing entity 20, which digital certificate is attested to the ownership of the public key by the signing entity 20.

This may be referred to as a post-certification scheme because the private key is used to generate a digital signature or digitally sign a transaction prior to receiving a digital certificate from the authentication and certification server 50.

Next, step 335 is performed to send the digital signature or digitally signed transaction and the digital certificate to the secure server 30.

The security server 30, or the receiving entity receiving the digital signature and digital certificate from the authentication and certification server 50, may then validate the instructions received from the signing entity 20 and process the appropriate transaction or perform the delivery of the goods and required services. The digital certificate and digital signature or digitally signed transaction can be easily verified by the receiving entity.

The OTPK module 40 is necessary for this embodiment. The OTPK module may be considered a software module that is completed on the signing entity 20, such as a pre-installed client plug-in, or is dynamically downloaded for use. The OTPK module 40 can perform its tasks without significant intervention from the user in operating the signing entity 20. The OTPK module 40 may be implemented as a PKCS #11 or CAPI DLL or JavaApplet or Active X plug-in embedded in an internet browser. The OTPK module may be automatically initiated by the signing entity 20 when performing secure transactions requiring digital signatures.

In another embodiment, the OTPK module 40 functions to perform the step of generating a new asymmetric key pair comprising a public key and a private key independently and without further instruction from the user. The OTPK module 40 may automatically establish communication with the authentication and certification server 50 for verifying the identity of the signing entity 20.

At this point, the user of the signing entity 20 may be prompted to enter a password, or the password may have been previously entered into the authentication and certification server 50 as part of the 2-factor authentication. The certificate request containing the public key is then sent to the authentication and certification server 50. The public key may be packaged into a PKC #10 block, a WS _ Security XML block, or a symmetric key wrapper block, and into a certificate request.

The private key is then automatically used to generate a digital signature of the signing entity 20 or may be used to digitally sign a transaction to be sent. Thereafter, the private key is no longer irretrievably deleted so that it cannot be reused or copied for future use. At the same time, the private key is thus always built into the signing entity 20 and is owned by the signing entity 20. The private key is unchanged by the signing entity 20 or the user from the time it is generated to the time it is irretrievably deleted. This meets important legal requirements for digital transactions over the internet using PKI.

Furthermore, the time period that the private key exists before being deleted is very short, and the private key has no chance to be stolen or copied elsewhere.

The OTPK module 40 receives a digital certificate from the authentication and certification server 50 certifying the ownership of the public key of the signing entity 20. The public key corresponds to the irretrievably deleted private key. The OTPK module then sends the digital certificate and the generated digital signature together to the secure server 30. The secure server 30 may then use the public key certified in the digital certificate to certify the authenticity of the digital signature.

The use of the OTPK module 40 enables the secure implementation of digital signatures using PKI. Thus an asymmetric key pair is generated for each transaction and the private key is irretrievably deleted once the digital signature is generated. The time that the private key exists before it is deleted is very short, and advantageously, the private key does not have the opportunity to be stolen or copied or reused.

The OTPK module further satisfies the law that requires that the private key always belongs to the user. A private key is generated that is used to generate a digital signature when belonging to a user and is then immediately irretrievably deleted.

In another embodiment, the OTPK module 40 may be used to generate asymmetric key pairs for separate time periods, rather than for separate transactions. When used for the setting of separate time periods, the generated private key is used to generate multiple digital signatures for multiple transactions as long as the user or initial phase of the signing entity 20 remains active. Once the user or the signing entity 20 expires the time period, the private key is once again irretrievably deleted to prevent the private key from being copied or reused.

In another embodiment, the OTPK module 40 may be used to generate asymmetric key pairs for use in a prior-certification setting. In this arrangement, a certificate request containing the public key is generated and sent to the authentication and certification server 50. The private key is then used to generate a digital signature, or to digitally sign a transaction, only after receiving the digital signature from the authentication and certification server 50. The pre-proof setting may also be used for a separate time period and for a separate transaction.

The present embodiment may advantageously forego the use of a smart card to store the private key. The new private key is generated when a digital signature needs to be generated and is then immediately deleted.

Furthermore, the time frame of the opportunity for copying the private key is very short. Once the private key is generated, a digital signature may be generated or a transaction digitally signed, and the private key may be deleted. The short existence of the private key and the lack of the need to store the private key makes it virtually impossible to copy and duplicate the private key.

The present embodiment further advantageously obviates the need to host a certificate from the CA, or in this case from the authentication and certification server 50. The need to maintain and upgrade LDAP systems is eliminated. In a conventional implementation of PKI, a user will often query LDAP to ensure that the public key used by the other party is still valid and sent by the correct owner of the issued digital certificate. In this embodiment, the digital signature is sent with the digital certificate, thereby rendering LDAP substantially irrelevant.

By using the OTPK module 40, CRL (certificate revocation List) and OCSP (Online certificate verification status protocol) also appear irrelevant. When the private key is lost, the CRL and OCSP have to be updated in the conventional PKI system. In this embodiment, the private key is never lost, and the public key is always revoked after use alone or for a separate period of time.

The present embodiment also advantageously provides ease of use for the user, as the OTPK module 40 does not require the user to understand the processes involved in generating a certificate request for a digital signature or valid certificate. Furthermore the user does not have to deal with the additional complications of having a smart card and having the smart card data (private key) read by a smart card reader.

The present embodiment also meets the regulatory requirements that the private key always belongs to the most authority of the signing entity 20 or user. The private key generated by the OTPK module 40 is only present for a short duration of time. The private key is always accompanied by the signing entity 20 and the user for this short duration.

The OTPK module 40 of the present embodiment is further not limited to any single asymmetric algorithm. Any of a variety of asymmetric algorithms such as RSA, DSA, and ECDSA may be implemented. Furthermore, different signing entities 20 may also use different symmetric algorithms in their OTPK modules 40.

In addition to using the OTPK module 40 in secure transactions over the internet, it has other applications in the field of digital rights protection. The digital original may be protected by an individual or an entity using a digital signature that proves ownership. Using information hiding (steganographic) techniques, digital signatures are often embedded to hide the digital signature in digital originals. Because such operations are often performed as one-time digital signatures for each work, it is well contemplated to use the OTPK module 40. An additional advantage of using the OTPK module 40 in digital rights protection is that the asymmetric keys and digital certificates for each work are always different. This makes it more difficult for a potential perpetrator to find and remove the digital signature and certificate from the digital original.

It will further be understood that, although embodiments have been described in detail, various modifications and improvements can be made by those skilled in the art without departing from the scope of the described embodiments.

Further, while embodiments have been described as being performed in various orders of steps, the steps described are not limited to, nor are they intended to be limited to, the order described. A person skilled in the art may carry out changes to the order of steps involved in the described embodiments without departing from the scope of the described embodiments.

Claims

1. A method of completing a transaction from a signing entity over a network to a receiving entity using a digital signature, the method comprising the steps of:

c) irretrievably deleting the private key;

2. The method of claim 1, wherein step b) further comprises:

b1) generating, by an one-time private key (OTPK) module, a new asymmetric key pair comprising a private key and a public key;

b2) generating a digital signature using the private key;

b3) generating a certificate request containing the public key;

b4) sending the certificate request to an authentication and certification server;

b5) receiving the digital certificate from an authentication and certification server certifying ownership of a public key;

b6) the digital signature is sent to a receiving entity along with the digital certificate.

3. The method of claim 1, wherein step b) further comprises:

b2) generating a certificate request comprising a public key;

b3) sending the certificate request to an authentication and certification server;

b4) receiving the digital certificate from an authentication and certification server certifying ownership of a public key;

b5) generating a digital signature using the private key;

4. A computer-implemented method for completing a transaction from a signing entity to a receiving entity over a network using a digital signature, the method comprising the steps of:

b) generating a certificate request comprising a public key;

c) generating a digital signature using a private key; and

d) irretrievably deleting the private key;

5. The method of claim 4, further comprising the steps of:

c) establishing communication with an authentication and certification server for authenticating the identity of the signing entity;

f) sending a certificate request containing the public key to an authentication and certification server;

g) receiving a digital certificate certifying ownership of the public key from the authentication and certification server; and

h) sending the digital signature and the digital certificate to a receiving entity.

6. The method of claim 4, further comprising, after step b) and before step c), the steps of:

b1) establishing communication with an authentication and certification server for authenticating the identity of the signing entity;

b2) sending a certificate request containing the public key to an authentication and certification server; and

b3) a digital certificate certifying ownership of a public key is received from an authentication and certification server.

7. The method of claim 6, further comprising after step d):

c) sending the digital signature and the digital certificate to a receiving entity.

8. A system for completing transactions over a network using digital signatures, comprising:

an OTPK module built into the signing entity for generating only a new asymmetric key pair comprising a public key and a private key, the OTPK module generating a digital signature using the private key and generating a certificate request containing the public key;

a certification and certification server for certifying the identity of the signing entity, for receiving a certificate request, and for issuing a digital certificate of public key ownership of the signing entity certificate;

9. The system of claim 8, wherein the OTPK module automatically sends the digital signature and digital certificate to the secure server.

10. The system of claim 8, wherein the OTPK module performs its functions without further intervention or instruction from the signing entity.

11. A computer-implemented method for using an OTPK module to complete a transaction of a signing entity with a receiving entity over a network using a digital signature at a new initial stage, the method comprising the steps of:

a) generating a new asymmetric key pair comprising a private key and a public key based on a notification that a transaction requiring a digital signature is desired;

b) generating a certificate request comprising a public key;

c) generating at least one digital signature using a private key; and

d) irretrievably deleting the private key;

12. The method of claim 11, further comprising the step of:

13. The method of claim 11, further comprising, after step b) and before step c), the steps of:

14. The method as recited in claim 11, further comprising, after step d), the steps of:

e) sending the digital signature and the digital certificate to a receiving entity.