CN111698093B - Digital timestamp issuing and verifying method based on PKI system - Google Patents

Abstract

The invention discloses a digital timestamp issuing and verifying method based on a PKI system, which comprises the following specific steps of: acquiring a digital certificate and a timestamp service provided by an authentication center; creating a message digest value of the medical record document based on a hash function; carrying out encryption operation on the message digest value by using private key data in the digital certificate according to an encryption principle to create a digital signature and sending the digital signature to a timestamp authority; decrypting the digital signature by using public key data in the digital certificate, and encrypting additional timestamp information in combination with private key data corresponding to the digital certificate to generate a new digital signature; the timestamp authority sends the new digital signature back to the sender along with its own digital certificate. The invention fully considers the time stamp authentication requirement of the medical record document digital signature, can better solve the problem that the time stamp authority possibly exists in the digital signature process and the user communicates with each other to change the credibility of the signature, and enhances the non-repudiation of the data.

Description

A digital timestamp issuance and verification method based on PKI system

technical field

The invention relates to the field of digital signature information security, in particular to a method for issuing and verifying digital time stamps based on a PKI system.

Background technique

With the increasing popularity of the Internet concept in recent years, electronic medical records will gradually replace traditional paper medical records and realize electronic management of personal health status and medical care information on the basis of meeting all diagnosis and treatment, legal and management needs. The emerging digital signature technology continues to develop, among which, the non-repudiation of the digital signature by the physician is one of the important functions of the digital signature. When a medical dispute occurs, there must be evidence to verify the identity of the physician or medical technician involved, but identification information alone is not enough, because the responsible physician or medical technician may tamper with the medical record after the event. In order to prevent the above situation If it occurs, it must be signed with a time stamp that is recognized by law and third parties.

Much work is focused on the issuance and verification process of timestamps. For example, a simple timestamp issuance step includes three steps: the user sends the medical record document W to the timestamp authority TSA, TSA appends the current time T and the unique ID of the document after W to form a new electronic signature S, TSA sends S sent to the user. However, the above time stamp protocol is not feasible in implementation, which involves the confidentiality of the medical record document W, the file integrity problem in the uploading and storage process, the resource utilization problem caused by the excessive file size, and the possible existence of The signature reliability problem of TSA and users colluding and deceiving; based on the above steps, relevant scholars have made improvements and proposed a TSA trusted timestamp scheme to replace the original medical record document W with the digest value H of the document, and use digital signatures in the transmission process. The technology can better solve the problems of confidentiality, integrity and resource utilization, but it does not technically solve the reliability problem of the timestamp authority and the user colluding with the user to change the signature in the process of digital signature.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a method for issuing and verifying digital time stamps based on the PKI system in view of the defects of the prior art, so as to solve the problems raised by the above background technology.

To achieve the above object, the present invention provides the following technical solutions: a digital time stamp issuance and verification method based on the PKI system, comprising the following steps:

Step (1): obtain the digital certificate provided by the PKI certification center CA and the time stamp service provided by the time stamp authority TSA;

Step (2): create the message digest value h of the XML medical record document W based on the hash function;

Step (1a): The physician applies for a digital certificate to the certification authority CA to obtain a legal identity;

Step (1b): The CA center authorizes TSA to provide time stamp services, issue digital certificates to it, and supervise its behavior (the digital certificate of TSA can be revoked if necessary);

Step (3): use the private key data in the digital certificate to encrypt the message digest value h according to the encryption principle to create a digital signature s=SIGdoctor(h), and send (s, h) and the digital certificate to TSA;

Step (4): TSA utilizes the public key data in the digital certificate to decrypt the digital signature s, and the additional time stamp information is encrypted in combination with the private key data corresponding to the digital certificate to generate a new digital signature S;

Step (4a): TSA utilizes the public key data in the sender's digital certificate in conjunction with the encryption algorithm to decrypt the received digital signature to obtain the message digest value H;

Step (4b): Compare the decrypted message digest value H and the original message digest value h; if they are not equal, send an error message to the requester; if they are equal, the exact time t and the current time when the requested time is received will be received. The overall data block composed of the serial number ID of the stamp request and the message digest value H is encrypted with the private key corresponding to the digital certificate to form a new digital signature S =SIG _TSA (ID, H, t);

Step (5): TSA sends back the new digital signature S and its own digital certificate to the sender, and performs a local save backup;

Step (6): The sender verifies the reliability of the TSA digital timestamp through the PKI mechanism;

Step (6a): the sender verifies the credibility of the TSA digital certificate through the PKI mechanism, if the verification is passed, the credibility of the digital timestamp is proved, and the digital signature S with the timestamp is preserved;

Step (6b): When the sender needs to verify the time when the XML medical record document W is generated, the PKI certification center CA can use the public key in the TSA digital certificate to verify the authenticity of the timestamp to clarify whether the document W has legal potency.

Beneficial effects of the present invention: a method for issuing and verifying digital timestamps based on the PKI system proposed by the present invention fully considers the timestamp authentication requirements of digital signatures of medical record documents, and at the same time can better solve the problems that may exist in the process of digital signatures. The time stamp authority TSA colluded with users to change the credibility of the signature, enhancing the non-repudiation of the data.

Description of drawings

Figure 1 is a flow chart of the present invention.

Detailed ways

The preferred embodiments of the present invention are described in detail below, so that the advantages and features of the present invention can be more easily understood by those skilled in the art, and the protection scope of the present invention can be more clearly defined.

Embodiment 1: Please refer to FIG. 1, the present invention provides a technical solution: a method for issuing and verifying digital time stamps based on the PKI system: the implementation steps of the present invention are as follows:

(1) Obtain the digital certificate provided by the PKI certification center CA and the time stamp service provided by the time stamp authority TSA;

(1a) The physician applies for a digital certificate to the certification agency CA to obtain a legal identity;

(1b) The CA center authorizes TSA to provide time stamping services, issue digital certificates to it, and supervise its behavior (the digital certificate of TSA can be revoked if necessary);

(2) The message digest value h of the XML medical record document W is created based on the hash function;

(3) Use the private key data in the digital certificate to encrypt the message digest value h according to the encryption principle to create a digital signature s=SIGdoctor(h), and send (s, h) and the digital certificate to TSA;

(4) TSA decrypts the digital signature s by using the public key data in the digital certificate, and encrypts the new digital signature S with the additional time stamp information in combination with the private key data corresponding to the digital certificate;

(4a) TSA decrypts the received digital signature using the public key data in the sender's digital certificate in combination with an encryption algorithm to obtain the message digest value H;

(4b) Compare the decrypted message digest value H with the original message digest value h; if they are not equal, send an error message to the requester; if they are equal, the exact time t at the time of the request and the current timestamp request will be received The overall data block composed of the serial number ID and the message digest value H is encrypted with the private key corresponding to the digital certificate to form a new digital signature S=SIG _TSA (ID, H, t);

(5) TSA sends the new digital signature S and its own digital certificate back to the sender, and performs a local save backup;

(6) The sender verifies the reliability of the TSA digital timestamp through the PKI mechanism;

(6a) The sender verifies the credibility of the TSA digital certificate through the PKI mechanism. If the verification is passed, the credibility of the digital timestamp is proved, and the digital signature S with the timestamp is saved;

(6b) When the sender needs to verify the time when the XML medical record document W is generated, the PKI certification center CA can use the public key in the TSA digital certificate to verify the authenticity of the time stamp to clarify whether the document W has legal effect.

In order to verify the validity of the method in this patent, based on the above-mentioned digital timestamp issuance and verification process, relying on the C# development environment and the Visual Studio2010 operating environment, a medical record timestamp issuance and verification system is designed, the core of which is for medical staff. Provides a timestamp service to facilitate timestamping medical record documents. The medical record timestamp uses the streaming socket Socket as the transmission basis, and the information of the request and response is packaged and transmitted. The medical record timestamp system adopts a client/server structure, and medical staff can log in to the IP address of the server and access the TSA service program on the server side to obtain the signature timestamp or verify the authenticity and validity of the timestamp online.

Among them, the client program mainly provides an easy-to-operate interface for medical staff to complete the request of the time stamp service and process the time stamp response information. The medical record documents that need to be time stamped are first subjected to digest calculation. In order to ensure the security of data transmission, the digest value must be signed, and finally the correct time stamp service request format data is formed, and sent to the server, and then waiting for processing. When the response information is returned, it is necessary to perform correctness analysis and integrity verification on the result data, as well as the verification of the reliability and validity of the certificate of the timestamp server, and finally, the obtained data is processed according to different applications.

The server-side program is the timestamp server, which is the core of the entire system, so the system functions are mainly concentrated on the server side, which mainly respond to client timestamp requests, issue timestamps, and store timestamp information. There are many users who accept timestamp requests on the server side. For security reasons, the server side will have multiple keys for signing, and the key management module can manage these keys safely and effectively. The database module is used to save timestamps and other related information for future client timestamp verification requests. The time source module can provide accurate and reliable time. The verification service module is responsible for verifying the identity of the requester.

In the digital timestamp issuance and verification process, common encryption and encoding algorithms have been implemented in .NET, which provides great convenience for coders. The namespace for implementing these algorithms is System.Security.Cryptography, which The namespace provides cryptographic services, including secure data encoding and decoding, and many other operations. Among them, the implementation of the hash function maps binary strings of arbitrary length to small binary strings of fixed length. A hash value is a unique and compact numerical representation of a piece of data. If a piece of plaintext is hashed, one of the punctuation marks is changed, and subsequent hash values will produce different values. Therefore, it is computationally nearly impossible to find two different inputs that hash to the same value. Therefore, the hash value of the data can verify the integrity of the data.

Public key encryption uses a private key that is kept secret from unauthorized users and a public key that is made public. Data encrypted with the public key can only be decrypted with the private key, while data signed with the private key can only be verified with the public key. The public key can be used by anyone; the key is used to encrypt data to be sent to the holder of the private key.

The main functions of the medical record timestamp issuance and verification system include the following. First, a public key and a private key are randomly generated using a hash function. The keys are in the form of XML Extensible Markup Language. These tags divide the document into many parts for identification. It is a way of storing data in a simple text format. Means it can be read by any computer and returns a string. Second, generate the required message digest MD for the plaintext information to be encrypted. Third, use the generated private key d to encrypt the generated message digest according to the encryption principle of the SA algorithm to obtain a digital signature. Fourth, verify the identity of another entity and protect the integrity of the data. That is, when a message is digitally signed using public key data, the sender first applies a hash function to the message to create a digest of the message. The sender then encrypts the message digest using the sent private key to create the sender's personal signature, since this private key uniquely identifies the sender, after receiving the message and signature, the recipient decrypts the signature using the sender's public key , to recover the message digest and hash the message using the uniform hashing algorithm used by the sender. If the message digest computed by the receiver exactly matches the digest of the message accepted from the sender, the receiver can determine that the message came from the sender.

The above-mentioned embodiments only represent several embodiments of the present invention, and the descriptions thereof are specific and detailed, but should not be construed as a limitation on the scope of the invention patent. It should be pointed out that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can also be made, which all belong to the protection scope of the present invention.

Claims (1)

1. a digital time stamp issuance and verification method based on PKI system, is characterized in that, comprises the steps: Step (1): obtain the digital certificate provided by the PKI certification center CA and the time stamp service provided by the time stamp authority TSA; Step (1a): The physician applies for a digital certificate to the certification authority CA to obtain a legal identity; Step (1b): The CA center authorizes TSA to provide timestamp services, issue digital certificates to it, and supervise its behavior; Step (2): create the message digest value h of the XML medical record document W based on the hash function; Step (3): use the private key data in the digital certificate to encrypt the message digest value h according to the encryption principle to create a digital signature s=SIGdoctor(h), and send (s, h) and the digital certificate to TSA; Step (4): TSA utilizes the public key data in the digital certificate to decrypt the digital signature s, and the additional time stamp information is encrypted in combination with the private key data corresponding to the digital certificate to generate a new digital signature S; Step (4a): TSA utilizes the public key data in the sender's digital certificate in conjunction with the encryption algorithm to decrypt the received digital signature to obtain the message digest value H; Step (4b): Compare the decrypted message digest value H and the original message digest value h; if they are not equal, send an error message to the requester; if they are equal, the exact time t and the current time when the requested time is received will be received. The overall data block composed of the serial number ID of the stamp request and the message digest value H is encrypted with the private key corresponding to the digital certificate to form a new digital signature S=SIG _TSA (ID, H, t); Step (5): TSA sends back the new digital signature S and its own digital certificate to the sender, and performs a local save backup; Step (6): The sender verifies the reliability of the TSA digital timestamp through the PKI mechanism; Step (6a): the sender verifies the credibility of the TSA digital certificate through the PKI mechanism, if the verification is passed, the credibility of the digital timestamp is proved, and the digital signature S with the timestamp is preserved; Step (6b): When the sender needs to verify the time when the XML medical record document W is generated, the PKI certification center CA can use the public key in the TSA digital certificate to verify the authenticity of the timestamp to clarify whether the document W has legal potency.

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