KR100681005B1 - Key roaming method, and method for the same - Google Patents

Abstract

The present invention relates to a key management infrastructure system, and in particular, in a public key infrastructure system (PKI system), the user's private key (secret key) regardless of the location without a separate media or device The present invention relates to a key roaming method and a system therefor, which makes it possible to use it safely. To this end, the present invention includes the steps of entrusting a private key of a specific user, temporarily restoring the entrusted private key according to a request of the user, and after the use of the key by the user is completed, the recovered private key. It is made to extinguish. Accordingly, the present invention provides a more convenient security environment for Internet users because the present invention works in conjunction with the PKI to maintain strong security anytime and anywhere and ensure mobility to the user.

Key Roaming, Key Consignment, Key Recovery, Cryptographic Protocol (PHP)

Description

Key roaming method, and method for the same

1 illustrates a system configuration for key roaming in accordance with the present invention.

2 is a state flow diagram illustrating a key roaming procedure according to the present invention.

3 is a diagram illustrating a key entrustment procedure according to the present invention.

4 shows the procedure for generating any R _i used in the present invention.

5 illustrates a key recovery procedure in accordance with the present invention.

6 is a diagram illustrating an example of key entrustment and key recovery according to the present invention;

* Description of Signs of Main Parts of Drawings *

10: Roaming Credential Server (RCS) 21 ~ 23: Roaming Confidential Server (RSS)

The present invention relates to a key management infrastructure system, and in particular, in a public key infrastructure system (PKI system), the user's private key (secret key) regardless of the location without a separate media or device It relates to a key roaming method and a system therefor that can be used safely.

In the past, as the Internet technology is used in various fields, the Internet security technology has been required.

In response to these demands, a standard for the asymmetric key algorithm RSA (Rivest, Shamir, Adelman) public key cryptosystem was published in 1991.

The channel encryption using the asymmetric key algorithm described above can successfully create a security session between a plurality of users and support the exchange of sensitive data online.

In addition, for the spread of services using asymmetric key algorithms, the concept of a certificate for proof of the owner of the public key is introduced. By issuing a certificate to an online user, the online users can authenticate each other and can also form mutually encrypted channels.

In addition, the use of electronic signatures by asymmetric key algorithms ensures the integrity of documents sent and received by online users.

Public Key Infrastructure (hereinafter referred to as PKI) provides the above-mentioned online channel security and security services such as user authentication and digital signature.

Among the methods of the PKI, ITU-T's X.509 method, which provides mutual authentication based on certificates generated from certificate authorities, is used as the standard.

In particular, the PKI defines the purpose of using keys as digital signatures and encryption for documents.

Looking at the characteristics of the digital signature and encryption for the document, respectively, in the case of the digital signature document, the certificate authority that issued the digital signature user's certificate or the certificate even when the private key of the key generator (user) is destroyed or damaged. The directory server, which stores certificates, makes it easy to obtain public key information that can verify digital signature values. However, in the case of an encrypted document, if the secret key of the user who encrypted the document is destroyed or damaged, the document itself is lost.

Because of the characteristics of digital signature and encryption for documents, the PKI standard recommends that security operations be performed using different key information for digital signatures and document encryption. It is recommended to use.

As these PKI-based services are successfully operated, various businesses such as electronic commerce, electronic payment, and electronic documentation have been progressing stably.

However, in an increasingly diversified business environment, there is a growing tendency to provide mobility to users or to remove the boundaries of existing systems while maintaining enhanced security.

Accordingly, in recent years, there is a demand that a more advanced management system for the keys used in the PKI be introduced in order to increase the mobility of users and support of various business models. In particular, in the case of Internet banking in Korea, even though the number of subscribers is on a global scale, there have been many inconveniences due to mobility proposals and security issues.

Of course, to address mobility constraints, some companies are using certificates and keys to carry additional hardware, such as smartcards or USB keys. However, this is not a perfect solution to ensure mobility because of the inconvenience of having to carry that extra hardware every time a user moves. In addition, in case of using the additional hardware in the PC room or abroad, there was a limit that the user could not use his own certificate and key without the equipment to recognize the additional hardware.

The present invention has been made to solve the problems of the prior art, the user can use his private key (private key) with the enhanced security of the public key infrastructure (PKI) at a remote location without using any additional hardware The present invention provides a key roaming method and a system therefor, which can be used safely.

The key roaming method according to the present invention for achieving the above object is a step of entrusting a private key of a specific user, and temporarily recovering the entrusted private key according to the user's request, Destroying the recovered private key after the key usage by the user is completed.                         

Preferably, in the key entrusting step, N R _i (i = 1 to N) values are generated from a registered password of the user, and N S _i (from a session key temporarily generated for encryption of the private key). generate i = 1 ~ N), derive the generated R _i (i = 1 ~ N) values into N + M K _j (j = 1 ~ (N + M), M> 0) values Correlation the derived K _{N + M} value and the generated S _N value with an exclusive OR, encrypt the user's private key with the correlation value, and register the same in a separate roaming credential server.

In addition, as the user requests the recovery of his or her private key using a registered password, recovers N R _i (i = 1 to N) values from the password and transfers them to the user terminal. Deriving the recovered R _i (i = 1 ~ N) value to N + M K _j (j = 1 ~ (N + M), M> 0) value, N roaming confidential servers (RSS), Receives the derived K _{1 ~ N} values and delivers S _{1 ~ N} values paired with the K _{1 ~ N} values to the user terminal, and in the user terminal, the received N S _i (i = 1 ~ Recovers the session key with an N) value, and, at the user terminal, calculates a correlation between the recovered session key and the derived K _{N + M} value with an exclusive OR, and at the user terminal, with the correlation value Decrypt the encrypted private key.

A feature of the key roaming system according to the present invention for achieving the above object is a roaming confidential server that encrypts a terminal of a specific user, a private key of the user, and separately registers encryption clues used to encrypt the private key. And a roaming credential server for storing the encrypted private key in the roaming confidential servers, automatically installing a virtual smart card to the terminal, and providing the encrypted private key to the virtual smart card.

Preferably, the virtual smart card automatically installed in the user terminal is automatically destroyed in the user terminal after the end of a specific service requiring the user's authentication.

Hereinafter, with reference to the accompanying drawings a preferred embodiment of the present invention will be described.

1 is a diagram illustrating a system configuration for key roaming according to the present invention.

Referring to FIG. 1, the system of the present invention includes a roaming credential server (hereinafter referred to as RCS) 10 and N roaming secret servers (hereinafter referred to as RSS). 23). In addition, user terminals 31 to 32 that interact with the system of the present invention, PKI service center 40 and PKI business center 50 are further configured. Here, the PKI service center 40 is one certification authority server. However, these additional components do not belong to the technical scope of the present invention, and generally perform known functions.

The system of the present invention is further provided with a virtual smart card (VSC). However, this virtual smart card (hereinafter, abbreviated as VSC) is a software concept as a control provided by the RCS 10 and automatically installed in the user terminals 31 to 32.

The most important point in the system of the present invention is that the computer used by the user, regardless of the location of the user, is the user terminals 31 to 32, and the user uses the RCS 10 through the user terminals 31 to 32. ), It automatically identifies itself through the VSC that is installed automatically, and receives the encrypted private key (secret key) accordingly to process the services of the PKI business center 50. Here, the PKI business center 50 is a place for servicing electronic commerce that requires internet banking or authentication.

The operation of the system of the present invention is described below.

The roaming credential server (RCS) 10 stores an encrypted private key (secret key). It also stores the certificate corresponding to that private key. Here, the private key (secret key) and the certificate are issued by the PKI service center 40. Separately, in the present invention, when the PKI service center 40 issues only a user's certificate, and the user requests the generation of a private key (secret key) using the issued certificate, the RCS 10 receives the user's private key (secret). It also supports the creation of key) and storing it with the certificate. This is a system implementation problem.

In addition, the RCS 10 provides a VSC that is automatically installed when the user connects through the user terminals 31 to 32 to the user terminals 31 to 32.

In particular, the RCS 10 stores the encrypted private key and at the same time stores a clue for authenticating the user who requested the encrypted private key. That is, when a user requests an encrypted private key using the clue when the key is to be recovered, the RCS 10 determines whether to provide the encrypted private key according to whether the clue matches the clue.

Next, a roaming secret server (RSS) 21 to 23 is a server that performs user registration and authentication, and stores private key encryption information through user registration and authentication. In particular, a secure socket layer (SSL) secure channel is used between the RSS 21 to 23 and the user terminals 31 to 32.

In particular, the present invention applies a password hardening protocol (PHP) based on asymmetric encryption (RSA) to RSS (21 to 23) and the user terminals (31 to 32). This ensures the security of the private key even with N-1 server attacks.

The RSS 21 to 23 register the user's identifier (ID) and password. At this time, the user transmits his or her private key while registering the identifier (ID) and password in the RSS (21 ~ 23).

Thereafter, the RSS 21 to 23 implement a cryptographic strengthening protocol (PHP) for the registered identifier (ID) and password. RSS (21 ~ 23) encrypts the private key received through the password enhancement protocol (PHP) to pass to the RCS (10), and RSS (21 ~ 23) stores the encryption clues used to encrypt the private key one by one Thereby entrusting the user's private key. Detailed procedures accordingly are described with reference to FIGS. 2 and 3.

The RSS 21-23 authenticates the user for key recovery. At this time, if the authentication is successful, the RSS 21 to 23 transmits the encryption clues corresponding to the registered password through the password enhancement protocol (PHP) to the user terminals 31 to 32.

Then, the user terminals 31 to 32 decrypt the encryption private key received from the RCS 10 through the cryptographic strengthening protocol (PHP).

The following describes a key roaming procedure according to the present invention. The key roaming procedure is explained by dividing the key entrusting process and the key recovering process.

2 is a state flow diagram illustrating a key roaming procedure according to the present invention.

The key roaming procedure of the present invention is described below with reference to FIG. In the following description, a first user terminal for entrusting a key by an initial user and a second user terminal for recovering a key thereafter are applied to explain the procedure of the present invention as the user moves.

Once the user connects to the RCS from the first user terminal (S1), the RCS provides the VSC to the first user terminal (S2). Then, the VSC is automatically installed in the first user terminal (S3).

Thereafter, the PKI service center (so-called certification authority server) generates a signature key pair (public key pair) from the first user terminal and requests for certificate issuance (S4), and generates a signature key pair of the corresponding user (S5). The certificate produced by the generated signature key pair is transferred to the first user terminal (S6).

Then, the user registers the identifier (ID) and password to the RSSs through the VSC installed in the first user terminal (S7). At this time, the user registers the identifier (ID) and password in the RSS to transmit his private key to the RSS.

RSS implements a password enhancement protocol (PHP) for the registered identifier (ID) and password (S8). See FIG. 3 for the procedure of the cryptographic protocol (PHP).

RSS generates N R _i (where i is 1 to N) values from the registered password through the password enhancement protocol (PHP) (S20). The R _i is generated through the process shown in FIG.

A generation procedure of R _i will be described with reference to FIG. 4. First, when a user registers an identifier (ID) and a password (P) to RSS through a VSC installed in the first user terminal, the RSS uses a registered identifier (ID) and the public key (PUK) and the public key certificate. Generate (PUC: Public key certificate) RSS generates random values n and e with the generated public key certificate (PUC). RSS generates a random value d with the generated public key PUK.

Thereafter, the registered password P, n value and e value are used, and r value is calculated as shown in Equation 1 by further using a predetermined k value.

r = f (P) * ke mod n

In addition, using the r value calculated by Equation 1, and the n value and d value generated above, the s value is calculated as in Equation 2 below. In Equation 1, f (P) is a value obtained by encrypting the password P with an arbitrary function.

s = r ^d mod n

Then, using the value of s calculated by Equation 2 and the predetermined k value above, R _i is generated as in Equation 3 below.

R = s / k mod n

R _i generated through the above procedure is used to generate a new K _j (where j is 1 to N + M, M> 0) using a key derivation function (KDF) (S21). N values of the generated K _j are registered one by one in N RSS (S22). More preferably, the generated R _i is used to generate a new K _j (where j is 1 to N + 2) using a key derivation function.

Again, RSS derives N S _i (where i is 1 to N) by applying a temporary session key generated for encryption of a private key (secret key) to a secret sharing algorithm (S23). The generated S _j N values are registered one by N RSS (S24).

N values and S _j N values among the generated K _j are registered in pairs in N RSS one by one.

In addition, RSS calculates a correlation between the K _{N + M} and S _N values through an exclusive OR operation (SOR), and encrypts the private key (secret key) using the correlation value (S26).

Thereafter, the encrypted private key value is registered in the RCS together with the K _{N + (M-1)} value (S27).

The key entrustment to the user is completed through the above-described cryptographic strengthening protocol (PHP) procedure.

Subsequently, when the user accesses the RCS from the second user terminal located at a remote location for recovering his private key (secret key) (S9), the RCS provides the VSC to the second user terminal (S10). Then, the VSC is automatically installed in the second user terminal (S11).

When the user logs in with an identifier (ID) and a password through the VSC installed in the second user terminal (S12), the RSS authenticates the user (S13).

If authentication is successful in the RSS, a key recovery procedure for the user is performed (S14). The key recovery procedure is shown in FIG.

First, each RSS transfers N R _i (where i is 1 to N) values from the registered password through a password enhancement protocol (PHP) to the second user terminal (S30).

The second user terminal generates K _j (where j is 1 to N + M, M 0) by applying the received R _i value to a key derivation function (S31).

Accordingly, the second user terminal transfers K ₁ to K _N values among the generated K _j values to each RSS (S32). Then, each RSS checks whether the received K _j value is the same as the value registered to it (S33), and if the same, delivers the S _i value paired with the K _j value registered to the second user terminal (S34). ). In addition, the second user terminal requests an encrypted private key registered in the RCS with a K _{N + (M-1)} value among the generated K _j values (S35). Then, the RCS transfers the encrypted private key stored corresponding to the value of K _{N + (M-1)} to the second user terminal (S36).

In operation S37, the second user terminal restores the temporary session key used for encrypting the private key (secret key) by applying the received S _i value inversely to a secret sharing algorithm.

The second user terminal also performs a correlation operation on the restored session key and the K _{N + M} value derived from the R _i value through a logical operation of an exclusive OR (S38).

As a result, the second user terminal decrypts the encrypted private key received from the RCS in advance as a correlation value between the restoration session key and the K _{N + M} value (S39).

Using the decrypted private key, the user processes the services of the PKI business center such as Internet banking or electronic commerce requiring authentication (S15).

When the service process ends (S16), the VSC installed in the second user terminal is automatically extinguished (S17). That is, in the present invention, the entrusted user's private key is temporarily decrypted for the service requiring authentication.

Next, an example of key entrustment and key recovery according to the present invention will be described with reference to FIG. 6. Here, RSS, which can be implemented in multiple numbers, is composed of RSS-1, RSS-2, and RSS-3.

RSS generates three R (R ₁ , R ₂ , R ₃ ) values using a password registered from a first user terminal through a password enhancement protocol (PHP) (S50). Then, the generated R ₁ / R ₂ / R ₃ is applied to a key derivation function to generate five new K ₁ / K ₂ / K ₃ / K ₄ / K ₅ (S51). Among the generated K ₁ / K ₂ / K ₃ / K ₄ / K ₅ , the K ₁ / K ₂ / K ₃ values are registered one by one in RSS-1, RSS-2, and RSS-3 (S52).

Again, RSS derives three S ₁ / S ₂ / S ₃ by applying a temporary session key generated for encryption of a private key (secret key) to a secret sharing algorithm (S53). The generated S ₁ / S ₂ / S ₃ values are paired with the K ₁ / K ₂ / K ₃ values and registered one at three RSS-1, RSS-2, and RSS-3 (S54).

In addition, RSS calculates a correlation between the K ₅ value and the S ₃ value through the logical operation of the exclusive OR (S55), and encrypts the private key (secret key) with the correlation value (S56).

Thereafter, the encrypted private key value is registered in the RCS together with the K ₄ value (S57).

This completes key entrustment for the user.

When the next key recovery procedure is implemented, each RSS first transmits three R ₁ / R ₂ / R ₃ to the user terminal from the registered password through the password enhancement protocol (PHP) (S58).

The user terminal generates five K ₁ / K ₂ / K ₃ / K ₄ / K ₅ by applying the received R ₁ / R ₂ / R ₃ value to a key derivation function (S59).

Accordingly, the user terminal delivers one K ₁ / K ₂ / K ₃ value to each RSS-1, RSS-2, and RSS-3 among the _five K ₁ / K ₂ / K ₃ / K ₄ / K ₅ values. (S60). Then, each RSS checks whether the received K value is the same as the value registered to it (S61), and if it is the same, delivers the S value paired with the K value registered to the user terminal (S62). In addition, the user terminal requests an encrypted private key registered in the RCS with the generated K ₄ value (S63). Then, the RCS transmits the encrypted private key stored in correspondence with the K ₄ value to the user terminal (S64).

In addition, the user terminal restores the temporary session key used for encrypting the private key (secret key) by applying the S ₁ / S ₂ / S ₃ value received from each RSS inversely to the secret sharing algorithm. (S65).

At the user terminal, the recovered session key and R A K ₅ value derived from the value is correlated through a logical operation of an exclusive OR (S66).

As a result, the user terminal decrypts the encrypted private key previously received from the RCS as a correlation value between the restoration session key and the K ₅ value (S67).

The present invention described above has the following effects.

First, it provides a more convenient security environment for Internet users because it works with PKI to maintain strong security anytime and anywhere and to ensure mobility to users.                     

Second, the enhanced security elements keep users safer than managing their own keys (moving with extra hardware).

Third, PCs used in homes, offices, or other people can use services that require higher security, such as Internet banking. In other words, in the present invention, while the user's certificate and key has been entrusted to the server, the user can return his or her certificate and key anytime and anywhere using his or her ID and password after accessing the server. Therefore, it is possible to access a system that requires authentication, such as Internet banking, and to perform a desired task using a certificate and a key obtained thereafter. At this time, the private key sent to the user is temporarily decrypted at the user's terminal (or computer) for work such as Internet banking or electronic signature, and is automatically destroyed when the user's work is completed. There is no fear of spillage.

Fourth, in the present invention, in support of key roaming, basically entrusting the user's encrypted private key and managing the temporary session key used to encrypt the private key into a plurality of pieces. Therefore, it is possible to prevent an illegal user from illegally obtaining a private key by speculation.

Claims (9)

A first step of entrusting a private key of a specific user; A second step of temporarily recovering the entrusted private key according to the user's request; And a third step of destroying the recovered private key after the use of the key by the user is completed. The method of claim 1, wherein the first step, Generate N R _i (i = 1 to N) values from the registered password of the user, N values of S _i (i = 1 to N) are generated from the temporarily generated session key for encryption of the private key, Deriving the generated R _i (i = 1 ~ N) value to N + M K _j (j = 1 ~ (N + M), M> 0) values, Correlate the derived K _{N + M} value with the generated S _N value with an exclusive OR; And encrypting the private key of the user using the correlation value and registering the same in a separate roaming credential server. The method according to claim 2, wherein R _i (i = 1 to N) value, Generate a public key (PUK) and a public key certificate (PUC) using the registered identifier (ID) and password (P) of the user, Generate a random value n and an e value with the generated public key certificate (PUC), generate a random value d with the generated public key (PUK), For values (f (P) * k ^e) multiplied by the k ^e for the password (P) for any k value predetermined as a value f (P) encrypted by the random function, the primary mod to the value of n Operation (f (P) * k ^e mod n), A second mod operation (r ^d mod n) is performed on the value of n with respect to the d multiplier value (r ^d ) of the result value (r) of the first mod operation, And a third-order mod operation (s / k mod n) by the n-value with respect to a value obtained by dividing the result value (s) of the second-order mod operation by the predetermined arbitrary k value. . The key roaming method of claim 2, wherein the generated S _{1 -N} values and the derived K _{1 -N} values are paired separately and registered in N roaming confidential servers (RSS). 3. The method of claim 2, wherein the encrypted private key is registered with the roaming credential server along with the derived K _{N + MX} (X≥1) value. The method of claim 2, As the user requests the recovery of his or her private key using the registered password, the N R _i (i = 1 to N) values are recovered from the password and transmitted to the user terminal. In the user terminal, the recovered R _i (i = 1 ~ N) value is derived by N + M K _j (j = 1 ~ (N + M), M> 0) values, N roaming confidential servers (RSS) are provided with the derived K _{1 ~ N} values and delivers S _{1 ~ N} values paired with the K _{1 ~ N} values to the user terminal, Recovering the session key from the received N S _i (i = 1 to N) values in the user terminal; In the user terminal, perform a correlation operation on the recovered session key and the derived K _{N + M} value with an exclusive OR; And in the user terminal, decrypt the encrypted private key with the correlation value. 7. The method of claim 6, wherein the encrypted private key is received from the roaming credential server using the derived K _{N + MX} (X≥1) value. A terminal of a specific user; Roaming confidential servers for encrypting the user's private key and separately registering encryption cues used to encrypt the private key; The roaming credential server is configured to store a private key encrypted in the roaming confidential servers, automatically install a virtual smart card to the terminal, and provide the encrypted private key to the virtual smart card. system. The key roaming system of claim 8, wherein the virtual smart card automatically installed in the user terminal is automatically extinguished in the user terminal after termination of a specific service requiring authentication of the user.

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