CN111159694A

CN111159694A - Private use authorization method of block chain digital assets based on zero knowledge proof

Info

Publication number: CN111159694A
Application number: CN201911302917.6A
Authority: CN
Inventors: 毛苇; 甘露
Original assignee: Shanghai Qiyin Information Technology Co ltd
Current assignee: Shanghai Qiyin Information Technology Co ltd
Priority date: 2019-12-17
Filing date: 2019-12-17
Publication date: 2020-05-15

Abstract

The invention discloses a private use authorization method of a block chain digital asset based on zero knowledge proof, which comprises the following steps: a user registration step; a step of registering digital assets; a digital asset authorization step; and (5) an authorization certification step. The invention can publish digital assets on a blockchain, but hide the owners of the digital assets; authorization for use of the digital asset may also be made on the chain, but the authorized purchaser, owner, and digital asset information are hidden.

Description

Private use authorization method of block chain digital assets based on zero knowledge proof

Technical Field

The invention relates to the technical field of blockchain, in particular to a private use authorization method of blockchain digital assets based on zero knowledge proof.

Background

In a block chain system which is represented by bitcoin and is designed by a UTXO model, the flow of each UTXO is public, the anonymity is ensured by hiding the corresponding relation between a person and an address, and once the corresponding relation between a certain address and the person is exposed, all transaction records and fund quantity of the person can be basically tracked by matching with data analysis tools on a chain. In an intelligent contract blockchain such as an etherhouse, all transactional data in a block is also public, although a virtual machine can provide a well-crafted programming language to implement arbitrary logic. The development of zero knowledge proof has enabled many users to attempt to implement private transactions over blockchains, the Nightfall project published before secure (EY), enabling support for private transfers of ERC-721 class assets at etherhouses. The ZCAh project designs a transaction record mixing scheme through zero knowledge proof, realizes the same function as a bitcoin, but does not store any specific information (sender, receiver, amount, etc.) of a transaction on a chain.

Items such as ZCash and Nightfall focus on the area of private transfers, but blockchains are used much more than Token transfers. The human society is experiencing a tremendous impact from the information revolution, and from the perspective of the enterprise, most enterprises are experiencing a transition from manufacturing to innovative enterprises. The core production data of enterprises is being converted from capital, factory building, raw materials and the like into a network formed by people, knowledge (information) and knowledge, and the professional expression is called social capital. In such a large context, the protection and efficient circulation of digital assets such as knowledge-based materials, results, etc. becomes especially important to the enterprise.

The registration of the assets is necessarily disclosed based on the ERC-721 standard, and after the registration of the assets, the assets are transferred into a privacy contract, and the transfer operation is not visible to the outside. In addition, in the case of digital assets of the type of articles, pictures, and the like, the most important way of circulation is not transfer of ownership but purchase of usage rights. Such as the reprint right purchase of articles, the purchase use of pictures, etc. For such digital assets, the use of NFT model abstraction is not sufficient, and private purchase of usage rights is even more impractical.

The applicant has therefore made an advantageous search and attempt to solve the above-mentioned problems, in the context of which the technical solutions to be described below have been created.

Disclosure of Invention

The technical problem to be solved by the invention is as follows: the method for authorizing the private use of the blockchain digital assets based on zero knowledge proof is provided for overcoming the defects of the prior art.

The technical problem to be solved by the invention can be realized by adopting the following technical scheme:

the private use authorization method of the blockchain digital assets based on zero knowledge certification comprises the following steps:

a user registration step: a user who needs to issue digital assets on a block chain registers according to an intelligent contract;

a digital asset registration step: the registered user registers own digital assets according to the intelligent contract;

a digital asset authorization step: when a registered user needs to anonymously authorize a part or all of the registered digital assets to one or more registered users, the registered user generates an authorization record on a block chain according to an intelligent contract and sends the generated authorization record to the authorized user;

and an authorization certification step: when one or more authorized users acquire the authorization of a certain digital asset, the one or more authorized users generate an authorization certificate for the received authorization record according to the intelligent contract so as to prove that the one or more authorized users acquire the authorization of the certain digital asset.

In a preferred embodiment of the present invention, the method further comprises a verification authorization step, wherein the verification authorization step is that when a registered user receives an authorization certificate provided by another registered user, the registered user verifies the validity of the received authorization certificate by calling an intelligent contract.

Due to the adoption of the technical scheme, the invention has the beneficial effects that: the invention can publish digital assets on a blockchain, but hide the owners of the digital assets; authorization for use of the digital asset may also be made on the chain, but the authorized purchaser, owner, and digital asset information are hidden. Therefore, the privacy of the whole process of publishing and authorizing the digital assets on the block chain is realized, and the record of publishing and authorizing all the assets is ensured not to expose the information of any participant in principle. If necessary, the user can prove ownership or use right of the assets to any third party by means of data on the blockchain and zero knowledge proof method.

Detailed Description

The present invention is further described in order to make the technical means, the creation features, the achievement purposes and the effects of the present invention easy to understand.

The invention discloses a private use authorization method of a blockchain digital asset based on zero knowledge certification, which comprises the following steps:

And (3) verifying and authorizing: when a registered user receives an authorization certificate provided by another registered user, the registered user verifies the validity of the received authorization certificate by calling an intelligent contract.

The specific content of the user registration step is as follows:

the user who needs to release digital assets on the block chain registers according to the intelligent contract, the registered user has a pair of public and private keys representing the ownership identity of the user assets, the length of each key is 32 bytes, and the key pairs are respectively marked as pk^R,sk^RAnd satisfies the relation:

pk^R＝h(sk^R)

the registered user also has a public and private key pair representing the identity of the blockchain and the corresponding blockchain address which are respectively marked as pk^E,sk^EAddr, is generated using a standard elliptic curve signature algorithm. The user needs to carefully keep the private keys in the two sets of public and private key pairs, and the private keys cannot be revealed。

The user also has a username n, which is provided to the querier upon verification of the authorization information, and which should be in the form of natural semantic information representing the user's identity.

The user can realize the anonymous authorization of the digital assets only by completing the user registration process according to the intelligent contract. The user registration actually records some important information of the user on the blockchain, and the pk of the user is recorded^RAnd one binding is made for three kinds of information of addr and n. Some of these information may not be changed, such as the user's blockchain address addr and pk representing the user's property ownership identity^R(ii) a Further information requires rights management, such as the user's registration name information n.

Accordingly, the following two points are ensured:

1. only possess sk^RCan be the corresponding pk^RUser registration operation is carried out, and zero knowledge proof is adopted for realization;

2. once the user has completed registration, only pk is owned^ECorresponding private key sk^ECan modify the user's registration name, and is realized by relying on an elliptic curve signature algorithm mechanism.

Note that there is an implicit requirement for both of the above: the private key of the user cannot be disclosed.

The following takes the user a as an example, and specifically introduces the user registration process:

1. generating two groups of public-private key pairs and other user information data in a secure environment;

2. generating a zero knowledge proof pi, containing a constraint:

–

3. open input:

4. private input:

5. calling an intelligent contract method: organ

Note: in the zero knowledge proof generation process of ZoKrates, it can be set whether the input variable is public, the public variable will appear in the generated proof, and the private variable will not appear.

The specific contents of the digital asset registration step are as follows:

for any digital asset, the user needs to generate a unique digital id for the digital asset, which is recorded as α.

Digital asset registration is actually recording the user's asset public key pk on the blockchain^Rα, the following two points are guaranteed according to the relationship:

1. only possess sk^RCan be the corresponding pk^RRegistering assets, which is realized by adopting zero knowledge proof;

2. the same α can only be registered once.

The following describes the process of digital asset registration by taking the user a registering the asset α as an example:

1. computing

2. Generating a zero knowledge proof pi, containing a constraint:

–

–

3. open input:

4. private input:

5. calling an intelligent contract method: register for shield

The specific contents of the digital asset authorization step are as follows:

the nature of authorization is to generate an authorization record on the blockchain that implies the asset α and the authorized party information.

1. Only registered asset α may be authorized, giving zero knowledge proof of the existence of the registration record for asset α;

2. the authorized party must have α the corresponding asset private key sk at registration time^RIt is necessary to give the authority to own the sk^RZero knowledge proof of (2);

3. the asset α, authorizer information, and authorizee information cannot be disclosed.

The following describes the process of digital asset authorization, taking user a as an example to authorize asset α to user B:

1. obtaining asset public key of user B

2. Computing

3. Obtaining

Namely, it is

At MT^RThe sibling node path value of top;

4. obtaining MT^RRoot node root of_R；

5. Generating a zero knowledge proof pi, containing a constraint:

–

–

–

–

6. open input:

7. private input:

8. invoking a contract method: (iii) shelf

The specific contents of the authorization certification step are as follows:

in order for a user to show a third party that he or she has obtained authorization for a digital asset, an authorization certificate needs to be generated. The authorization certification essentially certifies the correspondence between the user and the authorization record on the blockchain, namely:

1.α and pk exist on the Block chain^RCorresponding authorization record Z^α；

2. The user owns pk^RCorresponding toPrivate key sk^R。

The following describes the process of generating an authorization credential by taking user B as an example to generate an authorization credential for asset α:

1. obtaining

Computing

2. Computing

3. Obtaining

Namely, it is

At MT^RThe sibling node path value of top;

4. obtaining

Namely, it is

At MT^ZThe sibling node path value of top;

5. obtaining MT^ZRoot node root of_Z；

6. Obtaining MT^RRoot node root of_R；

7. Generating a zero knowledge proof pi, containing a constraint:

–

–

–

–

–

8. open input:

9. private input:

disclosed to all as proof that user B has the authorization of asset α from a.

The specific contents of the authentication and authorization steps are as follows:

for the authorization certification provided by other users, the validity of the authorization certification can be verified by calling the method of the intelligent contract:

Shield.authorizeCheck

the method returns:

whether B obtains the authorization of A;

2. user information of authorizer a;

3. user information of authorized party B.

Intelligent contract

The invention uses a series of intelligent contracts to realize the interaction with the block chain, which mainly comprises the following classes:

user-related: for user registration, username modification, etc.;

shield contract: for a user to initiate registration, authorization, authentication, etc. of an asset;

verifier contract: the elliptic curve pairing function is used to verify the zero knowledge proof as library for other contract invocations.

Two important intelligent contract contents are specifically described below:

Organization.sol

·register

-registering a user on the blockchain, recording the correspondence of the user's registration name, the asset public key and the blockchain address

·resetName(n_A):

-modifying the user name, with only the user registered blockchain address having authority to invoke

·get(pk^R)

-obtaining the asset public key pk^RCorresponding user registration name

Shield.sol

·register

-registering the digital asset α on the blockchain, where the information of user a is hidden;

–

will be saved to MT^RRemoving;

updating MT^R；

-generating α corresponding ERC-721token, owner for Shield contract.

·authorize

Authorization of digital assets α to B, where the information of digital assets α is hidden-contracts require verification that the root was or happens to be an MT^RRoot node of

·verify(π,inputs)

-verifying whether a proof pi and corresponding input matches by calling a method of a Verifier contract

·authorizeCheck

The proof of authorization information is verified.

The present invention may publish digital assets on a chain, but hide the owners of the digital assets. For example: post pictures are taken as an example. For example, a user a may register a picture on the blockchain, and the blockchain has no original content of the picture, but only the hash value and ID of the picture. This picture is also not visible from the blockchain as from user a. Next, if the user a needs to prove ownership of the picture, the user a may attach a piece of "text" when publishing the picture on a certain media, and take the piece of text to the block chain for querying, so as to prove that the user a is the author of the picture. But by the data on the blockchain alone, anyone cannot find out which other pictures user a has. Even if other people have the text, the proof of ownership cannot be forged, and the pictures cannot be sold.

The present invention can also conduct authorization of use of digital assets on the chain, but hide the authorized purchaser, owner, and digital asset information. For example, a certain user B sees a picture on the medium and may pay to purchase usage rights, but no one knows from whom the user B bought what. When the purchased picture is used in the blog of the user B, the user B can be attached with a text, and the validity of the payment purchase of the user B can be confirmed on the chain through the text, but any other purchase records of the user B cannot be found, and the user B cannot be found from who the picture is purchased.

Through the functions, the invention realizes the whole-process privacy protection of picture publishing and purchasing. While also enabling disclosure of some information as necessary to prove ownership and not expose any other additional private information.

It should be noted that although the present invention uses pictures as examples, the functions implemented by the present invention can be used in the registration and authorization of any type of digital asset.

The foregoing shows and describes the general principles and broad features of the present invention and advantages thereof. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, which are described in the specification and illustrated only to illustrate the principle of the present invention, but that various changes and modifications may be made therein without departing from the spirit and scope of the present invention, which fall within the scope of the invention as claimed. The scope of the invention is defined by the appended claims and equivalents thereof.

Claims

1. The method for authorizing the private use of the blockchain digital assets based on zero knowledge certification is characterized by comprising the following steps of:

2. The method of claim 1, further comprising a verification authorization step, wherein when a registered user receives an authorization certificate provided by another registered user, the registered user verifies the validity of the received authorization certificate by invoking an intelligent contract.