KR102354044B1 - The method of recovering private key using mnemonic code - Google Patents

Abstract

Provided is a method for recovering a private key using a mnemonic code executed in a computing device. The method of the present invention comprises: a first step of generating 18 mnemonic codes and a master seed using a password set by a user in a user node; a second step of generating a wallet using the master seed generated in the first step and a PIN code set in the user node; a third step of transmitting a public key of the wallet generated in the second step and an account name of the user node to a server; a fourth step of generating, by the server, an electronic signature using the account name transmitted from the user node and a private key of the server; a fifth step of randomly generating, by the server, a salt to generate a secrete key of the user node with an electronic signature generated in the fourth step, and then transmitting the secrete key to the user node; a sixth step of encrypting, by the user node, the mnemonic codes generated in the first step through the secret key transmitted in the fifth step, and transmitting the same to the server; and a seventh step of storing, by the server, the account name transmitted in the fourth step, the salt generated in the fifth step, and the encrypted mnemonic codes transmitted in the sixth step in a database. Therefore, a decentralized private key recovery system with enhanced security can be implemented.

Description

The method of recovering private key using mnemonic code}

The present invention relates to a private key recovery method using a mnemonic code. More specifically, individuals using a mnemonic code that can enhance security through a decentralized private key recovery service and further strengthen security by performing private key recovery using a password and PIN CODE that only the user can know It relates to a key recovery method.

Block chain refers to a data distribution processing technology in which all users participating in the network distribute and store all data to be managed. It is also called 'Distributed Ledger Technology (DLT)' or 'Public Transaction Ledger' in that the ledger containing transaction information is not owned by the transaction subject or a specific institution, but is a technology shared by all network participants. . Blockchain is a name given to the fact that blocks containing transaction contents are linked like a chain. This block chain is a technology to prevent hacking, such as forgery or forgery of transaction contents, and it sends transaction details to all users participating in the transaction and uses a method to prevent data forgery by comparing it with each transaction.

The core concept of blockchain is decentralization, which aims for P2P (Peer to Peer) transactions, away from the existing financial system that secures and manages all transactions in financial institutions. P2P refers to a communication network that connects personal computers without a server or client, and each connected computer acts as a server and client and shares information. By sharing and verifying the same data by multiple nodes, a trust relationship is formed in the digital world. This environment makes it possible to realize smart contracts that can conveniently conclude and modify contracts with P2P without intermediaries.

In the existing financial system, financial companies have kept transaction records on a central server, whereas in a blockchain based on the P2P method, transaction information is stored in blocks, connected in turn, and shared by all participants.

And, in order for all transaction information on the block chain to be recorded in a block, a valid signature is required, and this signature is performed by a valid digital key. A digital key consists of a pair of a private key and a public key. The public key serves as a bank account number, and the private key serves as a password for the account. Therefore, private key management is an important issue, and high attention is required because there is a possibility that a problem may occur when the private key is lost. However, if the private key is lost, recovery is quite difficult or impossible, resulting in loss of the rights to the corresponding digital asset. Accordingly, the present invention proposes a method for recovering and regenerating a lost private key.

Korean Patent Registration 10-1857223 (Announcement Date May 11, 2018)

The technical problem to be solved by the present invention is a master seed randomly generated using a mnemonic code in case the private key, which is a digital key used for recording transaction information in the block chain network, is lost, and only the user can know. It is to provide a private key recovery method using a mnemonic code with enhanced security by recovering the private key using the existing password and PIN CODE.

However, the technical problems to be solved by the present invention are not limited to the above problems, and may be variously expanded without departing from the technical spirit and scope of the present invention.

The private key recovery method using a mnemonic code according to an embodiment of the present invention for solving the above problems is a method executed in a computing device, and 18 mnemonic codes and a master seed are obtained using a password set by a user in a user node. The first step of generating, the second step of creating a wallet using the master seed generated in the first step and the PIN CODE set in the user node, the public key of the wallet created in the second step and a third step of transmitting the account name of the user node to a server, a fourth step of the server generating an electronic signature using the account name transmitted from the user node and the private key of the server, the server randomly A fifth step of generating a salt and generating the secret key of the user node together with the digital signature generated in the fourth step, and transmitting the secret key to the user node, the user node receiving the A sixth step of encrypting the mnemonic code generated in the first step through the secret key and transmitting it to the server, and the server includes the account name transmitted in the fourth step and the salt generated in the fifth step and a seventh step of storing the encrypted mnemonic code received in the sixth step in a database.

In the private key recovery method using a mnemonic code according to an embodiment of the present invention for solving the above problems, after the seventh step, the user node sends the encrypted mnemonic code and the secret key together with the certificate for self-authentication to the server Eighth step of requesting, the server verifies the certificate transmitted by the user node, and if the certificate is valid, a ninth step of reading the data of the user node stored in the database, the server is the account name stored in the database and a tenth step of generating an electronic signature through the private key of the server, an eleventh step of the server recovering the private key of the user node using the digital signature generated in the tenth step and the salt stored in the database step, the server transmits the encrypted mnemonic code stored in the database and the secret key of the user node recovered in step 11 to the user node, a 12th step, wherein the user node receives the A thirteenth step of decrypting the mnemonic code through the secret key of the user node, and recovering the master seed through the previously set password of the user node, and the user node using the previously set PIN CODE and the Step 13 A 14th step of restoring the wallet through the restored master seed is included.

Other specific details of the invention are included in the detailed description and drawings.

According to the present invention, even if the private key used for recording transaction information in the block chain network is lost, it can be recovered, and the fear of losing the right to tangible/intangible assets due to the loss of the private key can be reduced.

In addition, according to the present invention, it is possible to implement a decentralized private key recovery system with enhanced security by performing private key recovery using a password and PIN CODE that only the user can know.

However, the effects of the present invention are not limited to the above effects, and may be variously expanded without departing from the spirit and scope of the present invention.

1 is a diagram for explaining a process of generating a mnemonic code and generating a master seed according to BIP39.
2 is a diagram for explaining a protocol for an input value when creating a wallet according to BIP44.
3 is a diagram illustrating a distributed processing system using a block chain to which the technical idea according to the present invention can be applied.
4 and 5 are block diagrams illustrating the connection of blocks used in a block chain system.
6 is a diagram illustrating a process of generating a private key and backing up a mnemonic code according to an embodiment of the present invention.
7 is a diagram illustrating a private key restoration process according to an embodiment of the present invention.
8 is a flowchart sequentially illustrating a private key recovery method using a mnemonic code according to an embodiment of the present invention.
9 is a block diagram of a computing device of a node according to an embodiment of the present invention.

Advantages and features of the present invention and methods of achieving them will become apparent with reference to the embodiments described below in detail in conjunction with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but will be embodied in various different forms, and only these embodiments allow the disclosure of the present invention to be complete, and common knowledge in the art to which the present invention pertains It is provided to fully inform those who have the scope of the invention, and the present invention is only defined by the scope of the claims.

The terminology used herein is for the purpose of describing the embodiments, and is not intended to limit the present invention. In this specification, the singular also includes the plural unless specifically stated otherwise in the phrase. As used herein, "comprises" and/or "comprising" refers to the presence of one or more other components, steps, operations and/or elements mentioned. or addition is not excluded.

Unless otherwise defined, all terms (including technical and scientific terms) used herein may be used with the meaning commonly understood by those of ordinary skill in the art to which the present invention belongs. In addition, terms defined in a commonly used dictionary are not to be interpreted ideally or excessively unless specifically defined explicitly.

Hereinafter, preferred embodiments of the present invention will be described in more detail with reference to the accompanying drawings. The same reference numerals are used for the same components in the drawings, and repeated descriptions of the same components are omitted.

BIP is an abbreviation of "Bitcoin Improvement Proposals," and is a document containing proposals for improving Bitcoin functions. Since Bitcoin has no formal structure, it is a standard way of conveying ideas. In other words, a BIP is a form of proposal written or published to discuss the technology of Bitcoin.

Regarding the type of BIP: ① As a standard track BIP, it is a BIP suitable for Bitcoin network protocol, block or transaction validation. This type of BIP is at the heart of the underlying technology of Bitcoin. ② Information BIP mainly focuses on issues such as design and general guidelines. That is, it is a proposal for issues such as extending a solution, changing a block, or changing a hashing protocol. ③ Process BIP is a proposed change to the Bitcoin process. Process BIP is similar to standard track BIP, with the difference that process BIP applies only outside the Bitcoin protocol.

Regarding the type of BIP, BIP32 is an information BIP, a document that describes the general format of an HD wallet (Hierarchical Deterministic Wallet) and how to build an HD wallet. In addition, BIP39 is a standard track BIP, a document explaining how to easily recover an HD wallet by creating a mnemonic code. In addition, BIP44 is a standard track BIP, a document that proposes a multi-currency and multi-account structure with five predefined tree-level structures. The present invention proposes a KMS (Key Management Service) system that provides a private key management and recovery service by utilizing the above-described BIPs.

1 is a diagram for explaining a process of generating a mnemonic code and generating a master seed according to BIP39. 2 is a diagram for explaining a protocol for an input value when creating a wallet according to BIP44.

In detail with respect to the BIPs, (1) BIP39 generates a mnemonic code and a master seed.

① The mnemonic code generation process randomly generates a 192-bit sequence consisting of 0's and 1's. The generated sequence generates a hash value through the SHA-256 hash function. 6 bits from the front of the generated hash value are concatenated after the previously generated sequence. A total sequence of 198 bits is generated, and the sequence is divided by 11 bits from the front. 18 words are created by mapping each divided sequence to a predefined word list table.

In this case, the table is mapped to different words using bits of 00000000000 to 11111111111 as indexes. For example, in a 4-bit sequence, if the sequence is 0010, the mapping table is < 00 - abandon, 01 - ability, 10 - army, 11 - zoo >, and the result is abandon, army (See Fig. 1).

② The master seed generation process creates a 512-bit master seed by executing the HMAC-SHA512 hash function 2048 times with the previously generated mnemonic code and salt. Here, the salt value is used as mnemonic + (ciphertext). The present invention is characterized in that the encrypted text is replaced with the user's password.

(2) BIP32 represents the wallet creation process. In the wallet creation process, first, the CKD (Child Key Derivation) function is used recursively 5 times to generate a wallet address. The CKD function takes two input values, the first input value is the parent key value, and the second input value is a random number between ^{0 and 2 32 -1.}

The CKD function creates a child key with the result value. When CKD(m,3) = b, CKD(b,5) = c, CKD(CKD(m,3),5) can be written, and it is simply written as m/3/5. Recursive means inserting the result of the previous CKD as the first input of the next CKD function. More specifically, in the first execution of number 5, the master seed is input as an input value, and a master private key is generated as a result value. The master public key is generated from the master private key. Afterwards, the two key pairs are put as input values of the CKD function, respectively, to generate a child private key and a child public key pair.

(3) BIP44 is a protocol for input values when creating a wallet. The input value is defined when creating a wallet address in BIP32. The structure of BIP44 is m / purpose / coin type / account / balance address / usable address index, m is the seed value, and the purpose is fixed to 44 by BIP44. Coin type specifies the type of cryptocurrency, and several cryptocurrencies are defined in a standard document called SLIP0044. The present invention uses 60 based on Ethereum. An account usually contains a value that can identify the account. The present invention uses the PIN CODE of the user node for this item. For the balance address, all blockchains except Bitcoin generally use 0. The address index is ^{a random number between 0 and 2 32} -1 and means the i-th wallet address.

In blockchain technology, the user's private key management issue is very important. However, it is very difficult to recover a user's private key without compromising decentralization. Accordingly, the present invention provides a private key recovery service by taking an efficient compromise between decentralization and centralization.

First, in the case of the existing private key recovery service, a process of encrypting the user's private key with a specific key and storing it in the server for recovery is used. At this time, depending on how the specific key that encrypts the private key is managed and how the service provider retrieves and uses this key, it is determined whether the key can be centrally controlled or not. Perhaps it can be said that most private key recovery services are centralized.

Decentralized private key recovery service refers to a service in which users must enter all data necessary for private key recovery without a centralized server. In general, a mnemonic code is used to provide a decentralized private key recovery service. In this case, the user must memorize a list of 12 to 24 listed words. If you forget the word list, the private key can never be recovered. Therefore, even if a relatively easy-to-remember mnemonic code is used instead of the private key composed of complex letters, it is not easy to memorize the word list completely. Accordingly, some users require a system capable of easily recovering the private key anytime, anywhere without the dependency of the terminal.

Hereinafter, first, a distributed processing system using a block chain to which the concept of the present invention can be applied will be described.

3 is a diagram illustrating a distributed processing system using a block chain to which the technical idea according to the present invention can be applied.

Referring to FIG. 3 , the distributed processing system 100 using the block chain is a distributed network system composed of a plurality of nodes 110-170. The nodes 110 to 170 constituting the distributed network 100 may be electronic devices having computing power, such as computers, mobile terminals, and dedicated electronic devices.

In general, the decentralized network 100 can store and refer to information commonly known to all participating nodes in a connected bundle of blocks called blockchain. The nodes 110-170 can communicate with each other and can be divided into a full node that stores, manages, and propagates the block chain and a light node that can simply participate in transactions. . In this specification, when referring to a node without further explanation, it often refers to a full node that participates in a distributed network and performs an operation to create, store, or verify a block chain, but is not limited thereto.

Each block connected to the block chain includes transaction details within a certain period, that is, transactions. The nodes can manage transactions by creating, storing, or verifying the blockchain according to their respective roles.

According to an embodiment, the transaction may represent various types of transactions. In one embodiment, the transaction may correspond to a financial transaction for indicating the ownership status of virtual currency and its change. In another embodiment, the transaction may correspond to a physical transaction for indicating the ownership status of the object and its change. In another embodiment, the transaction may correspond to an information sharing process to indicate the recording, storage and transfer of information. Nodes performing a transaction in the distributed network 100 may have a private key and a public key pair each cryptographically related.

4 and 5 are block diagrams illustrating the connection of blocks used in a block chain system.

Referring to FIG. 4 , the block chain 200 is a kind of distributed database of one or more sequentially connected blocks 210 , 220 , 230 . The block chain 200 is used to store and manage user's transaction details in the block chain system, and each node participating in the network of the block chain system creates a block and connects it to the block chain 200 . Although a limited number of blocks 210 , 220 , and 230 are illustrated in FIG. 2 , the number of blocks that can be included in the block chain is not limited thereto.

Each block included in the block chain 200 may be configured to include a block header 211 and a block body 213 . The block header 211 may include a hash value of the previous block 220 to indicate a connection relationship between blocks. In the process of verifying whether the block chain 200 is valid, the connection relationship in the block header 211 is used. The block body 213 may include data stored and managed in the block 210 , for example, a transaction list or a transaction chain.

Referring to FIG. 5 , the block header 211 may include a hash 2112 of a previous block, a hash 2113 of a current block, and a nonce 2114 . Also, the block header 211 may include a root 2115 indicating a header of a transaction list in a block.

As described above, the blockchain 200 may include one or more connected blocks. The one or more blocks are connected based on a hash value in the block header 211 . The hash value 2112 of the previous block included in the block header 211 is the same as the current hash 2213 included in the previous block 220 as a hash value of the previous block 220 . The one or more blocks are chained by the hash value of the previous block in each block header. Nodes participating in the distributed network verify the validity of a block based on the hash value of the previous block included in the one or more blocks, so it is impossible for a single malicious node to forge or alter the contents of an already created block do.

The block body 213 may include a transaction list 2131 . The transaction list 2131 is a list of blockchain-based transactions. For example, the transaction list 2131 may include a record of financial transactions made in the blockchain-based financial system. The transaction list 2131 may be expressed in the form of a tree, and for example, the amount transmitted by user A to user B is recorded in the form of a list, and the storage length in the block is the length of the transaction included in the current block. It can be increased or decreased based on the number.

In addition, the block 210 may include other information 2116 other than the information included in the block header 211 and the block body 213 .

Nodes participating in a decentralized network have the same blockchain, and the same transactions are stored in blocks. A block containing a list of transactions is shared on the network, so all participants can verify it.

Hereinafter, a method for recovering a private key using a mnemonic code according to an embodiment of the present invention will be described. The private key recovery method using a mnemonic code according to an embodiment of the present invention is an algorithm executed in a computing device.

6 is a diagram illustrating a process of generating a private key and backing up a mnemonic code according to an embodiment of the present invention.

Referring to FIG. 6 , first, the user node generates 18 mnemonic codes and a master seed using the password set by the user in the BIP39 process (S100). A mnemonic code is a list of 12 to 24 words to recover a wallet, and a seed is used to keep randomness when generating a random number.

Next, the user node creates a wallet using the master seed generated in step S100 and the PIN CODE set in the user node through the BIP32 and BIP44 processes (S110).

Next, the user node transmits the public key of the wallet generated in step S110 and the account name of the user node to the server (S120).

Next, the server creates an electronic signature using the account name received from the user node and the server's private key (S130).

Next, the server generates a salt at random, generates a secret key of the user node together with the digital signature created in step S130, and transmits the secret key to the user node (S140). Salt is used to safely protect original data from malicious attackers by making it difficult to create a lookup table that enables a brute-force attack.

Next, the user node encrypts the mnemonic code generated in step S100 through the secret key of the user node received in step S140 and transmits it to the server (S150).

Next, the server stores the account name received in step S130, the salt generated in step S140, and the encrypted mnemonic code received in step S150 in a database (S160).

7 is a diagram illustrating a private key restoration process according to an embodiment of the present invention.

Referring to FIG. 7 , first, a user node requests an encrypted mnemonic code and a secret key together with a certificate for self-authentication from the server (S200).

Then, after verifying the certificate transmitted by the user node, the server fetches the data of the user node stored in the database if the certificate is valid (S210).

Next, the server generates an electronic signature through the account name stored in the database and the server's private key (S220).

Then, the server recovers the secret key of the user node using the digital signature generated in step S220 and the salt stored in the database (S230). Since the secret key of the user node contains the same input value as the secret key of the previously generated user node, it can be recovered with the same secret key as the previously created secret key of the user node.

Next, the server transmits the encrypted mnemonic code stored in the database and the secret key of the user node recovered in step S230 to the user node (S240).

Next, the user node decrypts the mnemonic code through the secret key of the user node received in step S240, and restores the master seed through the previously set password of the user node (S250).

Next, the user node restores the wallet through the previously set PIN CODE and the master seed restored in step S250 (S260).

8 is a flowchart sequentially illustrating a private key recovery method using a mnemonic code according to an embodiment of the present invention.

The present invention generates an array of 12 to 24 random words by generating a key of random 128 to 256 bits based on BIP39 in the user's terminal. The master seed is created by combining the words created above and the salt consisting of “Mnmonic” + password.

And, an HD wallet is created through the master seed created based on BIP32.

And, based on BIP44, a set of 2^32 private keys using the PIN CODE of the wallet application as the account value is generated and used.

In the case of change, it is fixed to 0 in the present invention because it is applicable only to Bitcoin. For example, the private key of the 14th address of the account with 123999 as the PIN code becomes m/44’/60’/123999’/0/15.

Then, the user's account name is hashed with the digital signature created by signing the server's backup private key and the salt randomly generated by the server to generate the user's private key.

By sending the corresponding private key to the client, the client encrypts the user's mnemonic code with the corresponding private key and sends it to the server. The server stores the password data in the database along with the salt of the user created above and the user's account name.

In this case, the server can easily find out the user's mnemonic code, but since it does not know the user's password and PIN CODE, it can be considered that it is decentralized in recovering the private key.

In addition, from the standpoint of a malicious hacker, even if the user's mnemonic code is found, the user's account can be hijacked only by finding the password and PIN CODE, so the security is further improved.

If the user wants to recover the account key, he/she requests data from the server by proving the ownership of the account. The server creates a digital signature by signing the account name that the user has proven ownership of with the server's backup private key as in the previous process. Accordingly, the generated digital signature is hashed with the salt stored along with the account name in the database to generate a secret key.

At this time, the generated secret key and the ciphertext stored in the database are sent together to the client. The user recovers the mnemonic code using the received secret key and ciphertext.

Then, enter the user's password and PIN CODE to recover the key set used for the account.

9 is a block diagram of a computing device of a node according to an embodiment of the present invention.

Referring to FIG. 9 , the computing device 1000 of a node according to an embodiment of the present invention includes a processor 1100 and a memory 1200 , and the processor 1100 includes one or more cores and a graphic processing unit and/or Alternatively, it may include a connection path (eg, a bus, etc.) for transmitting and receiving signals with other components.

The processor 1100 according to an embodiment executes the operation of the private key generation algorithm described with reference to FIG. 4 by executing one or more instructions stored in the memory 1200 .

For example, the processor 1100 collects information about user identification authentication and private key generation generated in one or more nodes by executing one or more instructions stored in the memory, and generates a transaction based on the collected information. Provides related information for at least one node.

Meanwhile, the processor 1100 may further include a random access memory (RAM) and a read-only memory (ROM) for temporarily and/or permanently storing signals (or data) processed therein. . Also, the processor 1100 may be implemented in the form of a system on chip (SoC) including at least one of a graphic processing unit, a RAM, and a ROM.

The memory 1200 may store programs (one or more instructions) for processing and controlling the processor 1100 . Programs stored in the memory 1200 may be divided into a plurality of modules according to functions.

The operations of the system described in relation to the embodiment of the present invention may be implemented directly in hardware, as a software module executed by hardware, or by a combination thereof. A software module may contain random access memory (RAM), read only memory (ROM), erasable programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM), flash memory, hard disk, removable disk, CD-ROM, or It may reside in any type of computer-readable recording medium well known in the art to which the present invention pertains.

The components of the present invention may be implemented as a program (or application) to be executed in combination with a computer, which is hardware, and stored in a medium. Components of the present invention may be implemented as software programming or software components, and similarly, embodiments may include various algorithms implemented as data structures, processes, routines, or combinations of other programming constructs, including C, C++ , may be implemented in a programming or scripting language such as Java, assembler, or the like. Functional aspects may be implemented in an algorithm running on one or more processors.

It is to be understood that the above-described embodiments are illustrative in all respects and not restrictive, and the scope of the present invention will be indicated by the following claims rather than the foregoing detailed description. And it should be construed that all changes and modifications derived from the meaning and scope of the claims as well as equivalent concepts are included in the scope of the present invention.

100: decentralized network
110-170: nodes
200: Blockchain
210, 220, 230: block

Claims (2)

A method executed on a computing device, comprising:
A first step of generating 18 mnemonic codes and a master seed using the password set by the user in the user node;
a second step of creating a wallet using the master seed generated in the first step and a PIN code set in the user node;
a third step of transmitting the public key of the wallet generated in the second step and the account name of the user node to a server;
a fourth step of generating, by the server, an electronic signature using the account name received from the user node and the private key of the server;
a fifth step of generating, by the server, a secret key of the user node together with the digital signature generated in the fourth step by randomly generating a salt, and then transmitting the secret key to the user node;
a sixth step of encrypting, by the user node, the mnemonic code generated in the first step using the secret key received in the fifth step, and transmitting the encrypted mnemonic code to the server; and
A seventh step of the server storing the account name transmitted in the fourth step, the salt generated in the fifth step, and the encrypted mnemonic code transmitted in the sixth step in a database; using a mnemonic code, including How to recover private key. The method of claim 1,
After the seventh step,
an eighth step of requesting, by the user node, an encrypted mnemonic code and a secret key together with a certificate for self-authentication from the server;
a ninth step of reading, by the server, data of the user node stored in the database if the certificate is valid after verifying the certificate transmitted by the user node;
a tenth step of generating, by the server, an electronic signature using the account name stored in the database and the private key of the server;
an eleventh step of the server recovering the secret key of the user node using the digital signature generated in the tenth step and the salt stored in the database;
a twelfth step of transmitting, by the server, the encrypted mnemonic code stored in the database and the secret key of the user node recovered in the eleventh step to the user node;
a thirteenth step of the user node decrypting the mnemonic code through the secret key of the user node received in the twelfth step, and recovering the master seed through the previously set password of the user node; and
The method of recovering the private key using a mnemonic code, further comprising: the user node recovering the wallet through the previously set PIN code and the master seed restored in the 13th step.

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