KR20030054546A - Session Key Sharable Simplex Information Service System And Method - Google Patents

Abstract

PURPOSE: An one-way information service system and a method capable of sharing a session key are provided to improve the security by generating and coding the session key at a server and transmitting it to a client. CONSTITUTION: A server(20) generates and certifies a session key for use in the coding of information to provide it to a subscriber. Then, the server(20) provides one-way coded information by using the session key. A client(30) restores the coded session key transmitted from the server(20) to share the session key with the server(20). The client(30) restores the coded information provided from the server(20) by using the session key to provide it to the subscriber. An ATM(Asynchronous Transfer Mode) exchanger(10) provides an one-way connection between the server(20) and the client(30).

Description

One-way information service system and method capable of sharing session key {Session Key Sharable Simplex Information Service System And Method}

The present invention relates to a one-way information service, and in particular, a session key is shared between a server and a client in a one-way information service system based on an asynchronous transfer mode (ATM) such as video on demand (VOD) or paid education broadcasting. A one-way information service system and method capable of sharing a session key to provide an information service are provided.

In recent years, as information is transmitted through various communication networks such as the Internet, security measures to prevent infiltration into the system and measures to protect the 'transmitted information' itself have been required. Encryption techniques such as secret key encryption and public key encryption have been developed.

In addition, the encryption algorithm can be broadly classified into a secret key encryption algorithm and a public key encryption algorithm. The secret key encryption algorithm uses the encryption key and the decryption key as the same, and the public key encryption algorithm uses different ones.

In addition, in the case of the public key encryption algorithm, since encryption and decryption time are very long compared to the secret key encryption algorithm, it is difficult to transmit the actual information to the public key encryption algorithm, and in the case of the secret key encryption algorithm, the system (server, In order to encrypt and decrypt between clients), it is necessary to have a secret key that only two systems know.

Therefore, while conventionally encrypting and decrypting actual information with a secret key cryptographic algorithm, the session key for this is exchanged and shared with the public key cryptographic algorithm, where DH (Diffie-Hellman), SSL (Secure Socket Layer) protocol, etc. The session key is shared by sending and receiving messages in both directions between the communicating systems using the same key sharing protocol.

However, according to the conventional encryption algorithm, a client receiving specific information shares a session key by connecting and receiving a message bidirectionally with a server using a key sharing protocol after connecting to the server, and the server shares information with a session key shared with the client. As encrypted data is transmitted, there is a problem in that a session key used for encryption cannot be shared in a unidirectional information service environment such as a video on demand (VOD) service.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object thereof is that, when a server and a client connected through an ATM switch have a one-way communication characteristic, the server generates and encrypts a session key for encrypting specific information, and then encrypts the client. By sharing the data with each other, a unidirectional information service system such as a VOD service or paid educational broadcasting enables sharing of a session key between a server and a client.

Another object of the present invention is to enable session key sharing between a server and a client in a one-way information service system, so that specific information can be encrypted and provided through the corresponding session key.

1 is a diagram schematically illustrating an ATM-based one-way information service system according to the present invention.

FIG. 2 is a block diagram showing an SA layer configuration of a server in FIG. 1; FIG.

3 is a block diagram illustrating the SA layer configuration of a client in FIG. 1; FIG.

4 is a view for explaining a procedure for providing specific information in the ATM-based unidirectional information service system according to the present invention.

Explanation of symbols on the main parts of the drawings

10: ATM exchanger 20: server

21, 31: public key management unit 22: session key generation unit

23, 32: session key DB 24: public key encryption unit

25: symmetric key encryption unit 33: public key decryption unit

34: symmetric key decoder

A feature of the present invention for achieving the above object is a server for generating and authenticating a session key for encrypting information to be provided to a subscriber and providing unidirectional encrypted information using the session key; ; A client for restoring the encrypted session key transmitted from the server to share the session key with the server, and restoring the encrypted information provided from the server using the session key to the subscriber; The present invention provides a one-way information service system capable of sharing a session key including an ATM switch that provides a one-way connection between the server and the client.

In this case, the server has an ATM layer for routing an ATM cell according to ATM cell header information, and a SAR layer and an application layer for converting the ATM cell into an AAL5 packet or performing an inverse transformation. And a SA layer for performing public key management function, an encryption function of information and session key, and a session key generation and authentication function to be used for information encryption. The basic protocol configuration includes an ATM layer for routing cells and a SAR layer and an application layer for converting the ATM cells into AAL5 packets or performing inverse transformation. And an SA layer performing a decoding function.

The server may include a session key DB for providing a management function such as storing / deleting / retrieving a session key; A session key generator for generating a session key used for encrypting information to be provided to a subscriber using a pseudo random number generator and storing the session key in the session key DB for each channel; A public key encryption unit for encrypting the session key using the public key of the subscriber and the private key of the server according to a public key encryption algorithm and transmitting the encrypted session key to the client of the subscriber through an ATM switch; For subscriber registration, the identification and public key of the subscriber are extracted from the public key directory of the accredited certification authority, and for the registered subscriber, after extracting the session key from the session key DB, the subscriber is transmitted along with the subscriber public key to the public key encryption unit. A public key management unit; And a symmetric key encryption unit that performs a symmetric key encryption function for encrypting information using a session key according to a symmetric key encryption algorithm, wherein the session key generator encrypts the information to ensure stability against retransmission attacks. And periodically regenerating and storing the session key used for the purpose.

In addition, the client, the session key DB for providing a management function such as storage / deletion / retrieval of the authenticated session key; A public key manager for authenticating a session key transferred from a server through an ATM switch and storing the authenticated session key in the session key DB; A public key decryption unit for restoring a session key authenticated by the public key management unit using a subscriber's private key and a server's public key according to a public key decryption algorithm; And a symmetric key decryption unit for providing a subscriber to restore the encrypted information transmitted from the server through the ATM switch using the session key stored in the session key DB.

On the other hand, another aspect of the present invention, the process of generating a session key for encrypting information to be provided to the subscriber at the server side and storing in the session key DB; Extracting the subscriber's public key by accessing the public key directory of an accredited certification authority after performing subscriber identity authentication when requesting the subscriber registration from the client side; Encrypting the session key extracted from the session key DB using the extracted subscriber's public key and the server's secret key and transmitting the encrypted session key to a client on the subscriber's side through an ATM switch; Restoring the encrypted session key of the server using the subscriber's private key and the server's public key, storing the session key in the session key DB, and sharing the session key with the server side. To provide a possible one-way information service method.

The encrypting of the session key to the client may include: encrypting the session key with a secret key of a server according to a public key encryption algorithm to perform authentication; Re-encrypting the session key encrypted with the secret key of the server using the subscriber's public key; And converting the session key encrypted with the private key of the server and the public key of the subscriber into a message together with the subscriber name information, converting the encrypted session key into an ATM cell, and restoring the encrypted session key to the server side. The sharing of the session key may include receiving, at the client side, an ATM cell copied by the ATM switch to recover a message with encrypted session key and subscriber name information;

And after the client extracts the session key encrypted using its private key, recovering the session key using the public key of the server according to a public key decryption algorithm.

Furthermore, in the above-described one-way information service method capable of sharing the session key, if the server wants to provide information to the subscriber, the session key is extracted from its session key DB, and then the information is encrypted using the extracted session key. Later transmitting to the client of the subscriber through the ATM switch; And retrieving the session key DB from the client side, extracting the session key, and restoring the encrypted information transmitted from the server to the subscriber.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

The present invention is to implement a one-way information service system based on Asynchronous Transfer Mode (ATM), which enables session key sharing. At this time, the one-way information service system based on ATM is unidirectional encrypted as shown in FIG. An information exchange server (20) providing information, one or more clients (30) receiving information provided from the server (20), and an ATM switch providing a one-way connection between the server (20) and the clients (30). (10) is provided.

Here, the server 20 and the client 30 are an ATM layer for routing ATM cells according to ATM cell header information, and a SAR (Segmentation And) for converting an ATM cell into an ATM Adaptation Layer 5 (AAL5) packet or performing inverse transformation. Reassembly) and the application layer as the basic protocol configuration, the server 20 is used for the client 30, that is, public key management function for subscriber registration and authentication, encryption function of information and session key, and information encryption. SA includes a security agent (SA) layer that performs a session key generation and authentication function, and the client 30 performs a public key management function for session key authentication of the server 20, and an SA that performs session key and information decryption functions. Contains the hierarchy.

In addition, the SA layer configuration of the server 20 will be described in more detail with reference to FIG. 2. The public key manager 21, the session key generator 22, the session key DB 23, and the public domain are described. It comprises a key encryptor 24 and a symmetric key encryptor 25.

The public key management block (21) extracts the subscriber's identity and public key from the public key directory on the Internet operated by an accredited certification authority (computer center, information security agency, VeriSign, etc.) to register the subscriber. For the subscriber, the session key is extracted from the session key DB 23 and then transmitted to the public key encryption unit 24 together with the subscriber public key.

The session key generation block 22 generates a session key used for encrypting specific information to be provided to the subscriber by using a pseudo random number generator and then sends the session key DB 23 to the session key DB 23. Store by channel, but periodically regenerate and save the session key to ensure stability against replay attacks (storing previous messages and then retransmitting them).

The session key DB (Session Key Data Base) 23 provides management functions such as storing / deleting / retrieval of the session key generated by the session key generator 22, and includes a session key generator 22 and a symmetric key encryption unit. Send and receive session keys through the interface between them.

The public key encryption engine 24 encrypts the session key using the subscriber's public key and the server 20's secret key according to the public key encryption algorithm, and then encrypts the session key with the ATM switch 10. Send to subscriber (ie client) through.

Symmetric Key Encryption Engine 25 performs a symmetric key encryption function that encrypts specific information using a session key according to a symmetric key encryption algorithm. Because the combination of the techniques, the encryption speed is faster than the public key algorithm based on the equation, and it is easy to implement in hardware. Therefore, the VOD service and pay that need to be encrypted and decrypted on the paid channel information in real time It is easy for real-time services such as educational broadcasting.

In addition, the SA layer configuration of the client 30 will be described in more detail with reference to FIG. 3. The public key manager 31, the session key DB 32, the public key decoder 33, and the symmetric key are described in detail. The decoder 34 is included.

The public key manager 31 authenticates the session key transmitted from the server 20 through the ATM switch 10, stores the session key in the session key DB 32, and the session key DB 32 stores the public key. It provides management functions such as storing / deleting / retrieving session keys authenticated by the management unit 31, and exchanges session keys through an interface between the public key management unit 31 and the symmetric key decryption unit 34.

The public key decryption unit 33 restores the session key to be authenticated by the public key management unit 31 using the subscriber's private key and the server 20's public key according to the public key decryption algorithm. The symmetric key decryption engine 34 restores the encrypted information using the session key.

The procedure for providing specific information through subscriber registration and session key sharing in the ATM-based one-way information service system configured as described above will be described with reference to FIG. 4 as follows.

First, on the server 20 side, the session key generation unit 22 of the SA layer performs a session key generation protocol and periodically generates a session key to encrypt specific information to be provided to the subscriber, and then the session key DB 23 Is stored in (step S41).

Subsequently, when there is a request to receive specific information of the server 20 from the client 30, the information necessary for subscriber ID and other identity authentication in the higher application program of the server 20 is transmitted to the public key manager 21. When requesting the subscriber registration by forwarding (step S42), the public key management unit 21 accesses the public key directory operated by an accredited certification authority and requests the subscriber public key after performing subscriber identity authentication. The subscriber's public key is extracted (step S43).

Further, the public key manager 21 retrieves the session key DB 23, extracts the session key used for encrypting specific information to be transmitted to the subscriber (step S44), and then shares the extracted session key with the public key directory. The public key of the subscriber, the secret key of the server 20, and the session key extracted from the server 20 are transmitted to the public key encryption unit 24 (step S45).

Then, the public key encryption unit 24 of the server 20 encrypts the session key using the subscriber's public key and the server 20's private key according to the public key cryptographic algorithm, and then converts the encrypted session key into an ATM switch ( 10) to the subscriber (step S46).

Accordingly, the public key decryption unit 33 of the SA layer in the client 30 on the subscriber side restores the encrypted session key using the subscriber secret key and the public key of the server 20 to the public key management unit 31. The server which is to transmit (step S47) and the public key management unit 31 stores the session key to be used for the restoration of the encrypted specific information in the session key DB 32 (step S48), thereby providing the one-way specific information to itself. The session key is shared with the (20) side.

In this state, if the application of the server 20 delivers specific information to be provided to the subscriber to the symmetric key encryption unit 25 (step S49), the symmetric key encryption unit 25 searches for the session key DB 23. After extracting the session key that is currently shared with the subscriber to provide specific information (step S50), using the session key extracted from the session key DB 23 in accordance with the symmetric key encryption algorithm, the specific information received from the application program After encryption, the data is transmitted to the subscriber via the ATM switch 10 (step S51).

Then, the symmetric key decoder 34 located in the SA layer in the client 30 on the subscriber side retrieves the session key DB 32 and extracts the session key to be used for restoring specific information provided from the server 20 ( Step S52), by using the extracted session key, the encrypted specific information on the server 20 side received through the ATM switch 10 is restored and then transferred to the application program (step S53), whereby the specific information restored to the subscriber is transmitted. It can be provided.

Meanwhile, in the above-described procedure for providing specific information through sharing the session key, the process of generating and encrypting the session key on the server 20 side will be described in more detail as follows, wherein the session key is the server 20 and the client who is the subscriber. Should be shared only between the 30 and 30, the server 20 generates an encrypted session key to be shared with the subscribers using a public key encryption algorithm.

That is, the session key generator 22 of the server 20 generates a session key to be shared with a registered subscriber, that is, a key for encrypting information to be provided to the subscriber, using a pseudo random number generator. Done.

Thereafter, the public key encryption unit 24 of the server 20 encrypts the session key using the private key of the server 20 and the public key of the subscriber according to the public key encryption algorithm. For example, the server 20 A) public key of 'pks' and private key of 'sks', and the public keys of two registered subscribers are defined as 'pka' and 'pkb', respectively. According to the public key encryption algorithm, the session key (assuming 'SK') is encrypted using the secret key (sks) of the server 20 as shown in Equation 1 below to authenticate the corresponding session key. The key encryption function 'E' becomes 'E_pks (E_sks (SK)) = SK', except that 'E_key' is a public key encryption function that encrypts 'key' as a key value.

E_sks (SK)

The public key encryption unit 24 of the server 20 encrypts the secret key using the public key pka and pkb of the corresponding subscriber so that only the registered subscriber can extract the session key SK. E_sks (SK) 'is encrypted as shown in Equation 2 below, and the result values are stored in the form of a subscriber table as shown in Table 1 below.

E_pka (E_sks (SK)), E_pkb (E_sks (SK))

Subscriber name Subscriber Public Key Session key to send to subscriber Client A (CA) pka E_pka (E_sks (SK)) CB (Client B) pkb E_pkb (E_sks (SK))

In this way, the public key encryption unit 24 which performs session key authentication and encryption transmits the corresponding encrypted session key to the clients 'CA' and 'CB', which are registered subscribers, through the ATM switch 10. In order to transmit the session key to subscribers 'CA' and 'CB', a message (M) of the form 'M = {CA, E_pka (E_sks (SK)), CB, E_pkb (E_sks (SK)))' is created. When the message M is converted into an ATM cell through the lower SAR layer and transmitted to the ATM switch 10 through the ATM layer, the message M is copied from the corresponding ATM switch 10 to the subscribers CA and CB. Will be sent.

Accordingly, each subscriber receives the ATM cell copied by the ATM exchanger 10, extracts its session key, and performs server authentication. At this time, the client 30 of the subscriber side accesses the ATM cell through the ATM layer. After reception, the message M transmitted from the server 20 through the SAR layer is restored and transmitted to the SA layer, and the public key decryption unit 33 of the SA layer transmits the message M from the server 20. Each encrypted authentication session key is extracted from.

That is, the subscriber 'CA' extracts the encrypted authentication session key 'E_pka (E_sks (SK))' and the subscriber 'CB' extracts the encrypted authentication session key 'E_pkb (E_sks (SK))', respectively. In addition, the authentication session key is extracted using its own private keys (ska, skb), in which case 'E_ska (E_pka (E_sks (SK))) = E_sks (SK)' for subscriber 'CA', In the case of the subscriber 'CB', 'E_skb (E_pkb (E_sks (SK))) = E_sks (SK)' is extracted.

Thereafter, the public key decryption unit 33 of the client 30 decrypts the extracted authentication session key into the public key (pks) of the server 20 according to the public key decryption algorithm and shares the session key ( SK) will be restored.

On the other hand, since the specific information that the server 20 provides to the client 30 requires a real-time characteristic, it cannot use a public key encryption algorithm that requires a lot of computation time, and thus, in the present invention, a symmetric key is used to secure specific information. An encryption algorithm is used, and the session key to be used for encryption is shared between the server 20 and the client 30 as a subscriber according to the above-described procedure before starting the service.

In addition, the embodiments according to the present invention are not limited to the above-described embodiments, and various alternatives, modifications, and changes can be made within the scope apparent to those skilled in the art.

As described above, in the present invention, when the server and the client connected through the ATM exchanger have a one-way communication characteristic, the server generates a session key for encrypting specific information, encrypts it, transmits it to the client, and then shares the VOD service. In the one-way information service system such as paid education broadcasting, the session key can be shared between the server and the client, and specific information can be encrypted and provided through the corresponding session key.

Claims (11)

A server for generating and authenticating a session key for encrypting information to be provided to a subscriber and providing unidirectional encrypted information using the session key; A client for restoring the encrypted session key transmitted from the server to share the session key with the server, and restoring the encrypted information provided from the server using the session key to the subscriber; And a ATM switch providing a one-way connection between the server and the client. The method of claim 1, The server has a basic protocol configuration such as an ATM layer for routing an ATM cell according to ATM cell header information, and a SAR layer and an application layer for converting the ATM cell into an AAL5 packet or performing inverse transformation. A single-way information service system capable of sharing session keys, comprising: a public key management function, an SA layer for performing information and session key encryption functions, and a session key generation and authentication function to be used for information encryption. The method of claim 1, The client may include an ATM layer for routing an ATM cell according to ATM cell header information, and a SAR layer and an application layer for converting the ATM cell into an AAL5 packet or performing an inverse transformation, and include session key authentication of a server. A unidirectional information service system capable of sharing a session key, comprising a public key management function and an SA layer performing a session key and an information decryption function. The method according to claim 1 or 2, The server includes a session key DB for providing a management function such as storing / deleting / retrieving a session key; A session key generator for generating a session key used for encrypting information to be provided to a subscriber using a pseudo random number generator and storing the session key in the session key DB for each channel; A public key encryption unit for encrypting the session key using the public key of the subscriber and the private key of the server according to a public key encryption algorithm and transmitting the encrypted session key to the client of the subscriber through an ATM switch; For subscriber registration, the identification and public key of the subscriber are extracted from the public key directory of the accredited certification authority, and for the registered subscriber, after extracting the session key from the session key DB, the subscriber is transmitted along with the subscriber public key to the public key encryption unit. A public key management unit; And a symmetric key encryption unit that performs a symmetric key encryption function for encrypting information using a session key according to a symmetric key encryption algorithm. The method of claim 4, wherein The session key generator is one-way information service system capable of sharing the session key, characterized in that for regenerating and storing the session key used to encrypt the information periodically to ensure stability against retransmission attacks. The method according to claim 1 or 2, The client may include: a session key DB for providing a management function such as storing / deleting / retrieving an authenticated session key; A public key manager for authenticating a session key transferred from a server through an ATM switch and storing the authenticated session key in the session key DB; A public key decryption unit for restoring a session key authenticated by the public key management unit using a subscriber's private key and a server's public key according to a public key decryption algorithm; And a symmetric key decryption unit for providing a subscriber to restore encrypted information transmitted from the server through an ATM switch using the session key stored in the session key DB. Generating a session key for encrypting information to be provided to a subscriber at a server side and storing the session key in a session key DB; Extracting the subscriber's public key by accessing the public key directory of an accredited certification authority after performing subscriber identity authentication when requesting the subscriber registration from the client side; Encrypting the session key extracted from the session key DB using the extracted subscriber's public key and the server's secret key and transmitting the encrypted session key to a client on the subscriber's side through an ATM switch; Restoring the encrypted session key of the server using the subscriber's private key and the server's public key and storing the encrypted session key in the session key DB to share the session key with the server side. One-way information service method capable of sharing session key. The method of claim 7, wherein The session key is a key for encrypting information to be provided to a subscriber at a server, and is generated using a pseudo random number generator according to a session key generation protocol. The method of claim 7, wherein The process of encrypting the session key to a client may include: encrypting the session key with a secret key of a server according to a public key encryption algorithm to perform authentication; Re-encrypting the session key encrypted with the secret key of the server using the subscriber's public key; And converting the session key encrypted with the private key of the server and the public key of the subscriber into a message together with the subscriber name information, converting the session key into an ATM cell and transmitting the same. The method of claim 7, wherein The process of restoring the encrypted session key and sharing the session key with the server side may include: receiving, at the client side, an ATM cell copied by an ATM switch, restoring a message having the encrypted session key and subscriber name information; Restoring the session key using the public key of the server according to a public key decryption algorithm after the client extracts the encrypted session key using the private key of the client; Information service method. The method of claim 7, wherein Extracting a session key from its own session key DB, encrypting the information using the extracted session key, and transmitting the information to the client of the subscriber through an ATM switch; The client side further searches for its own session key DB, extracts the session key, and restores the encrypted information transmitted from the server to the subscriber. Way.