CN101222612A - A method and system for securely transmitting media streams - Google Patents

Abstract

The present invention provides a method and system for securely transmitting media streams, specifically: a key generation unit is set in advance, and the key generation unit acquires encryption capability information of a terminal during a call flow, and generates a key for media according to the encryption capability information. Stream key; then send the generated key to the terminal and the media stream carrying device respectively; the terminal and the media stream carrying device use the obtained key to transmit the media stream. By applying the scheme of the present invention, the calling terminal and the called terminal do not generate keys themselves, but the keys are generated by the key generation unit, without the need for clock synchronization and the support of the public key infrastructure (PKI) system, which can greatly Reduce the complexity of end-to-end media stream key negotiation, facilitate the promotion of media stream encryption services and meet the actual needs of legal interception.

Description

A method and system for securely transmitting media streams

technical field

The invention relates to media stream encryption technology, in particular to a method and system for safely transmitting media streams.

Background technique

Media streams are generally transmitted based on Real-time Transport Protocol (RTP, Real-time Transport Protocol), and the media streams mentioned here are audio media streams, video media streams, and the like. However, since the RTP protocol itself does not involve security issues, there are security risks such as leaks and attacks during the transmission of media streams.

In order to enhance the security of media streams during transmission, various methods for generating and distributing keys, ie, key agreement methods, have been proposed. Afterwards, the terminal can use the assigned key to transmit the media stream, so as to achieve the purpose of securely transmitting the media stream.

In the prior art, there are two typical methods in the key agreement method: one is the Multimedia Internet Key (MIKEY) public key mode, and the other is the MIKEY DH mode.

Among them, the basic idea of the MIKEY public key mode is: the calling terminal generates a key and an envelope key, the key is encrypted with the envelope key, and the envelope key is encrypted with the public key of the called terminal certificate, and then Send the encrypted key to the called terminal through the MIKEY protocol, and the called terminal obtains the key after decrypting it, and completes the key negotiation process.

In the MIKEY public key mode, in order to ensure the safe and smooth progress of the key negotiation process, clock synchronization between the calling terminal and the called terminal is required, and the support of the public key infrastructure (PKI) system is required. However, in practical applications, it is more complicated to implement clock synchronization and PKI system support, which is not conducive to the realization of key agreement. For example: in a conference call, there are multiple terminals that need to transmit media streams. If the media streams of multiple terminals are to be encrypted, the clocks of the multiple terminals need to be synchronized, which greatly increases the difficulty of key negotiation. Another example: the calling terminal and the called terminal are ordinary mobile terminals, and due to the large number of mobile terminals, it will be difficult to complete certificate management and other work in the PKI system, and key negotiation cannot be carried out smoothly.

The basic idea of MIKEY DH mode is: the calling terminal and the called terminal generate DH values separately, then use the MIKEY protocol to exchange each other's DH values, and then generate keys according to the DH values of both parties.

The MIKEY DH mode also requires clock synchronization, and the implementation of the MIKEY DH mode is very complicated, with a large amount of calculation and high requirements on terminal performance, which is not conducive to the realization of key agreement.

In addition, in practical applications, the operator needs to obtain the key in the media stream in order for the security agency to meet the requirements of lawful interception. In the prior art, only the terminals participating in the interaction can obtain the key. The terminals participating in the interaction mentioned here may be two terminals, the calling terminal and the called terminal, or multiple terminals. Any third party other than the interaction may None of them can obtain the key, that is, they cannot meet the requirements of lawful interception.

Contents of the invention

The present invention provides a method and system for securely transmitting media streams, which can avoid processes such as clock synchronization, PKI support, and certificate management under the condition of ensuring link security, reduce the complexity of key generation, and facilitate media stream encryption services. promote.

In order to achieve the above object, the technical scheme proposed by the present invention is:

A method for securely transmitting media streams, presetting a key generation unit, the method includes the following steps:

A. The key generation unit obtains the encryption capability information of the terminal during the call flow, and generates a key for the media stream according to the encryption capability information;

B. Send the generated key to the terminal and the media stream carrying device respectively;

C. The terminal and the media stream bearing device transmit the media stream using the obtained key.

In the above solution, the key generation unit is a functional unit of the call session control function entity CSCF on the calling side, and the terminal is the calling terminal, then the method for the key generation unit in step A to obtain the encryption capability information is specifically as follows:

The calling terminal initiates a call, and sends a call request message carrying its own encryption capability information to the calling CSCF, and the calling side CSCF obtains the encryption capability information of the calling terminal from the call request message.

In the above solution, the encryption capability information of the calling terminal is carried in the Session Description Protocol SDP of the call request message; or carried in the Session Initiation Protocol SIP calling attribute receiving negotiation Accept-contact header field of the call request message; or carried In the SIP extension negotiation field in the call request message, the SIP extension negotiation field is a supported field; or carried in the field defined by the RFC 4568 standard in the call request message.

In the above scheme, the method of sending the key to the calling terminal described in step B is:

When the CSCF at the calling side receives the call response message from the called terminal, it carries the key generated in advance in the call response message and sends it to the calling terminal.

In the above scheme, the media stream bearing device is the calling side media agent MP, and the method of sending the key to the calling side MP in step B is:

The CSCF at the calling side sends the message carrying the key to the resource and access control subsystem RACS at the calling side, and the RACS at the calling side sends the key to the MP at the calling side.

In the above scheme, the step C is specifically:

When the media stream is transmitted from the calling terminal to the called terminal, the calling terminal uses the obtained key to encrypt the media stream, and transmits the encrypted media stream to the MP on the calling side, and the MP on the calling side uses the obtained key decrypt the media stream and transmit the decrypted media stream; and/or

When the media stream is transmitted from the called terminal to the calling terminal, the MP on the calling side uses the obtained key to encrypt the media stream from the called terminal, transmits the encrypted media stream to the calling terminal, and the calling terminal uses The obtained key decrypts the media stream.

In the above solution, the key generation unit is a functional unit in the CSCF on the called side, and the terminal is the called terminal, then the method for obtaining the encryption capability information in step A is specifically as follows:

The called terminal receives the call request message from the calling terminal through the called-side CSCF, and returns the call response message carrying the encryption capability information of the called terminal to the called-side CSCF, and the called-side CSCF obtains from the call response message Encryption capability information of the called terminal.

In the above scheme, the method of sending the key to the called terminal as described in step B is:

When the CSCF at the called side receives the message related to the call from the calling terminal, it carries the key generated in advance in the message related to the call and sends it to the called terminal.

In the above scheme, the media stream bearer device is the MP on the called side, and the method of sending the key to the MP on the called side as described in step B is:

The CSCF at the called side sends the message carrying the key to the RACS at the called side, and the RACS at the called side sends the key to the MP at the called side.

In the above scheme, the step C is specifically:

When the media stream is transmitted from the calling terminal to the called terminal, the MP on the called side uses the acquired key to encrypt the media stream of the calling terminal, and transmits the encrypted media stream to the called terminal. to decrypt the media stream; and/or

When the media stream is transmitted from the called terminal to the calling terminal, the called terminal uses the obtained key to encrypt the media stream, and transmits the encrypted media stream to the called side MP, and the called side MP uses the obtained key again Decrypt the media stream, and then transmit the decrypted media stream.

For the second purpose of the invention, the technical solution proposed by the present invention is:

A system for securely transmitting media streams, including a terminal, a media stream bearing device, and the system also includes a key generation unit;

The terminal is used to send its own encryption capability information to the key generation unit, obtain the key, and be responsible for transmitting the media stream according to the key;

The media stream bearing device is used to receive the key generated by the key generation unit, and is responsible for transmitting the media stream according to the key;

The key generating unit is configured to receive encryption capability information input by the terminal, generate a key, and send the generated key to the terminal and the media stream carrying device respectively.

In the above solution, the key generation unit is a functional unit in the P-CSCF, the media stream bearing device is an MP, and the system further includes:

RACS is used to receive the key generated by the key generation unit in the P-CSCF, and forward the key to the MP.

To sum up, the present invention proposes a method and system for securely transmitting media streams. The terminal itself does not generate the key, but the key generation unit generates the key, without the need for clock synchronization and without the support of the PKI system. It can greatly reduce the complexity of key generation, achieve the purpose of securely transmitting media streams, and facilitate the promotion of media stream encryption services. Since the calling side and the called side can independently generate their own keys without negotiating with each other, the process of generating and issuing keys does not affect the execution of the call process. In addition, since the transmission between the media stream bearing devices on the calling side and the called side is in plain text, the actual requirement of lawful interception can be met.

Description of drawings

Fig. 1 is a flow chart of the present invention;

Fig. 2 is a schematic diagram of a message flow in a method embodiment;

Fig. 3 is the basic structural diagram of the system of the present invention;

Fig. 4 is a structural diagram of a system embodiment.

Detailed ways

In order to make the purpose, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

The basic idea of the present invention is: a key generation unit is set in advance, which is responsible for the generation and distribution of keys; terminals and media stream bearing devices use the keys obtained from the key generation unit to transmit media streams, so as to achieve the purpose of securely transmitting media streams .

Fig. 1 is a flow chart of the present invention. As shown in Figure 1, the present invention comprises the following steps:

Step 101: The key generation unit acquires encryption capability information of the terminal during a call flow, and generates a key for media streams according to the encryption capability information.

Step 102: The key generating unit sends the generated key to the terminal and the media stream carrying device respectively.

Step 103: The terminal and the media stream bearing device transmit the media stream using the obtained key.

Since the call process involves the calling side and the called side, the present invention realizes the secure transmission of the media flow and is correspondingly divided into two cases: the calling side and the called side.

For the calling side, the terminal is the calling terminal; the key generation unit is the calling side key generation unit, and the calling side key generation unit may be a functional unit in the calling side CSCF; the The media stream bearing device is the calling side media stream bearing device, that is, the calling side MP.

In this case, the method for obtaining the encryption capability information of the calling terminal in step 101 is: the calling terminal initiates a call, sends a call request message carrying its own encryption capability information to the calling CSCF, The encryption capability information of the calling terminal is obtained from the call request message.

Correspondingly, the method for sending the key to the calling terminal in step 102 is: when the CSCF on the calling side receives the call response message from the called terminal, carry the key generated in advance in the call response message sent to the calling terminal.

Correspondingly, the method for sending the key to the MP on the calling side described in step 102 is: the CSCF on the calling side sends the message carrying the key to the resource and access control subsystem RACS on the calling side; The RACS then sends the key to the MP on the calling side.

At this point, both the calling terminal and the calling-side MP have obtained the key from the calling-side P-CSCF, and can use the key to transmit the media stream. The transmission media stream described here can be divided into two situations:

One situation is: when the media stream is transmitted from the calling terminal to the called terminal, the calling terminal uses the obtained key to encrypt the media stream, and transmits the encrypted media stream to the calling side MP, and the calling side MP then The obtained key is used to encrypt the media stream, and then the decrypted media stream is transmitted, that is, to the called side.

Another situation is: when the media stream is transmitted from the called terminal to the calling terminal, the MP on the calling side uses the obtained key to encrypt the media stream from the called terminal, and transmit the encrypted media stream to the calling terminal , the calling terminal then uses the obtained key to decrypt the media stream.

In practical application, the media stream may be transmitted only from the calling terminal to the called terminal, or only from the called terminal to the calling terminal, or both the calling terminal and the called terminal may transmit media streams to each other.

For the called side, the terminal is the called terminal; the key generation unit is the called side key generation unit, and the called side key generation unit may be a functional unit in the called side CSCF; The media stream bearer device is the called side media stream bearer device, that is, the called side MP.

In this case, the method for obtaining the encryption capability information of the called terminal in step 101 is: the called terminal receives the call request message from the calling terminal through the called side CSCF, and will carry the encryption capability information of the called terminal itself The call response message is returned to the CSCF at the called side, and the CSCF at the called side obtains the encryption capability information of the called terminal from the call response message.

Correspondingly, the method for sending the key to the called terminal in step 102 is: when the CSCF at the called side receives a call-related message from the calling terminal, carry the key generated in advance in the call-related message. The message is sent to the called terminal. The message related to the call mentioned here may be a confirmation message or an information change message.

Correspondingly, the method for sending the key to the MP on the called side in step 102 is: the CSCF on the called side sends the message carrying the key to the RACS on the called side, and the RACS on the called side sends the key to the MP on the called side. Called side MP.

At this time, both the called terminal and the MP on the called side have obtained the key from the P-CSCF on the called side, and can use the key to transmit the media stream. Similar to the calling side, the transmission media stream described here can be divided into two cases:

One situation is: when the media stream is transmitted from the calling terminal to the called terminal, the MP on the called side uses the obtained key to encrypt the media stream of the calling terminal, and transmits the encrypted media stream to the called terminal. Ask the terminal to decrypt the media stream by using the obtained key.

Another situation is: when the media stream is transmitted from the called terminal to the calling terminal, the called terminal uses the obtained key to encrypt the media stream, and transmits the encrypted media stream to the MP on the called side, and the MP on the called side Then use the obtained key to encrypt the media stream, and then transmit the decrypted media stream.

In the present invention, both the calling side and the called side generate keys independently, and deliver the generated keys to the terminal and the media stream bearing device at this side. That is to say, when a certain side generates a key, since the key is only used to transmit media streams in the area to which this side belongs, while both the calling side and the called side use clear text transmission outside the area, so, in When generating a key, it does not need to negotiate with the other party, nor does it need to send the key generated by itself to the other party.

It should be noted that the present invention uses the calling side or the called side to illustrate the method of secure media stream transmission, but in practical applications, the calling process and the media stream transmission will involve both the calling side and the called side. In order to better illustrate the solutions of the present invention, the following preferred embodiments involve both the calling side and the called side, so as to fully describe the method for securely transmitting media streams.

method embodiment

In this embodiment, the key generation unit is set on the calling side and the called side in advance, the calling side key generating unit is a functional unit in the calling side P-CSCF, and the called side key generating unit is the called side A functional unit in the P-CSCF; of course, in practical applications, the key generation unit may not be a functional unit in the P-CSCF, but an independent server.

In this embodiment, the calling side further includes the calling terminal, the calling side RACS, and the calling side MP; the called side further includes the called terminal, the called side RACS, and the called side MP.

In addition, it is assumed that the key generated by the P-CSCF at the calling side is x, and the key generated by the P-CSCF at the called side is y.

Fig. 2 is a schematic diagram of message flow in this embodiment. As shown in Figure 2, this embodiment includes the following steps:

Step 201: The calling side initiates a call, and sends a call request message carrying its own encryption capability information to the calling side P-CSCF.

The call request message described here is the INVITE message in the SIP protocol, and four methods can be used to carry the encryption capability information of the calling terminal in the INVITE message: the first method is to carry in the SDP of the INVITE message; the second The method is carried in the SIP caller attribute acceptance negotiation (Accept-contact) header field in the INVITE message; the third method is carried in the extended negotiation domain of SIP in the INVITE message; the fourth method is carried in the INVITE message soliciting In the fields defined by the standard for comments (RFC4568).

For the first bearer method, that is, bearer in the Session Description Protocol (SDP), the format of the encryption capability information is:

m=<media><port>srtp/avp<format-list>

[a=media_encryption:

SRTP&

[Lists of the Encrypted Algorithms]&

[Lists of the Encrypted Key Length]&

[Lists of the Message Authentication Algorithms]&

[Lists of the Message Authentication Key Length]&

[Key Generation side declaration]&

[Key derivation rate];]...

Among them, the m field carries media information and supports media capability declaration; the a field is used to describe the attributes of the media stream, and the meanings of these attribute descriptions are shown in Table 1:

Table I

If the calling terminal specifies: SRTP protocol, AES-CM encryption algorithm, encryption key length of 128 bits or 256 bits, message authentication and integrity protection algorithm using HMAC-SHA1, message authentication and integrity protection key length 160 bits, and the key update rate is 24, then the key capability information in the call request message is:

m=<media><port>srtp/avp<format-list>

a=media_encryption:SRTP&AES-CM&128;256&HMAC-SHA1&160&24

For the second bearer method, that is, bearer in the SIP calling attribute Accept-contact header field, its format is:

Accept_Contact: *; media_encryption =

"SRTP&

[Lists of the Encrypted Algorithms]&

[Lists of the Encrypted Key Length]&

[Lists of the Message Authentication Algorithms]&

[Lists of the Message Authentication Key Length]&

[Key Generation side declaration]&

[Key derivation rate]”;. …

Wherein, the meanings of each subfield in the media_encryption field are the same as those in Table 1, and will not be repeated here.

If the encryption capability information of the calling terminal is the same as the first method, its format is: Accept_Contact:media_encryption="SRTP&AES-CM&128;256&HMAC-SHA1&160&24"

For the third bearer method, that is, bearer in the extended negotiation field of SIP, the capability information of the calling terminal can be directly written into the Supported header field, for example:

Supported: media_encryption=SRTP-[AES-CM]-[128;256;512]-[HMAC-SHA1]-[160]

The meanings of the subfields are the same as those in Table 1, and will not be repeated here.

For the fourth bearer method, that is, bearer in the field defined by RFC 4568, its format is:

a=crypto:1AES_CM_128_HMAC_SHAI_80

inline:

The meanings of the subfields are also the same as those in Table 1, and will not be repeated here.

Step 202: The P-CSCF at the calling side sends a call request message to the P-CSCF at the called side.

Step 203: The key generation unit in the P-CSCF on the calling side generates a key x according to the encryption capability information of the calling terminal.

In this embodiment, the newly added key generation unit is a functional unit in the P-CSCF, and it can also be used in other CSCFs, such as the S-CSCF.

If the key generation unit is not a functional unit in the P-CSCF but an independent server, an interface between the P-CSCF and the server needs to be provided, and the P-CSCF obtains the generated key from the server through the interface.

Step 204: The P-CSCF at the calling side initiates a resource reservation process. During the resource reservation process, the P-CSCF at the calling side sends the generated key x to the RACS at the calling side.

Step 205: The RACS at the calling side sends the key x to the MP at the calling side.

Here, the steps 204 and 205 are resource reservation processes, which mainly determine the quality of service (Qos), threshold control and other information, and send the determined Qos, threshold control and other information to the calling side MP through a policy delivery message . During the resource reservation process, the P-CSCF can extend a Media-Sub-Component data-value pair (Media-Sub-Component AVP) in the Media-Component-Description (Media-Component-Description) in the resource request message (AAR) For a field carrying a key, such as a Media-Encryption-Key field, record the generated key in this field, and send the key to the RACS at the calling side. The expanded format can be:

Media-Component-Description::=<AVP Header:519>

{Media-Component-Number}

*[Media-Sub-Component]

[AF-Application-Identifier]

[Media-Type]

[Max-Requested-Bandwidth-UL]

[Max-Requested-Bandwidth-DL]

[Flow-Status]

[RS-Bandwidth]

[RR-Bandwidth]

[Media-Encryption-Key]

Among them, [Media-Encryption-Key] is an extended field for carrying the key.

Of course, in practical applications, the key may not be sent to the RACS on the calling side through the AAR message, but delivered through other messages, such as resource modification messages, etc. How to deliver and how to expand is related to the specific implementation , which will not be repeated here.

After receiving the key, the RACS at the calling side can send the key to the MP at the calling side through the H.248 protocol or the Common Open Policy Service (COPS) protocol.

If the RACS at the calling side sends a COPS message to the MP at the calling side, its format is:

<Decision Message>::＝<Common Header>

<Client Handle>

*(<Decision>)|<Error>

[<Integrity>]

<Decision>::=<Context>

<Decision Flags>

[<Named Decision Data:Provisioning>]

<Named Decision Data:Provisioning>::＝<Install Decision>

<Install Decision>::＝*(<PRID><EPD>)

At this point, you can specify: Op Code＝2, Flags＝1 in the Common Header; the Client Handler object is mandatory; specify Command-Code＝1 (Install) in the Decision object, Flags＝0x02; in the Named Decision Data:Provisioning object Specify C-Num=5; expand the Media-Encryption-Key field in the Install Decision object to carry the key received by the RACS on the calling side.

If the key is delivered through the H.248 protocol, when using the Add command to add an endpoint to the association, the key can be carried based on the stream description (Stream Descriptor) of the Media Descriptor, that is, the Diameter The value of the Media-Encryption-Key field in the message is copied to the characteristic identifier SDP_A and encryptkey of the MediaDescriptor.

In addition, after receiving the call request message in step 202, the P-CSCF on the calling side continues to execute the subsequent call process, that is, executes step 206; while generating and issuing a key, that is, executes steps 203 to 205. In other words, the subsequent call process and key generation and distribution are two parallel processes, and there is no strict sequence in time.

In addition, in this embodiment, the P-CSCF on the calling side sends the key to the MP on the calling side by initiating a resource reservation process. The key is sent to the MP on the calling side. In other words, as long as the generated key can be sent to the calling MP.

Step 206: The P-CSCF at the called side sends the call request message to the called terminal.

Step 207: The called terminal returns a call response message carrying its encryption capability information to the called P-CSCF, and the called P-CSCF obtains the encryption capability information of the called terminal from the call response message.

Here, the call response message is related to the call request message received by the called terminal, and may be a 183 message or a 200 OK message.

Step 208: The P-CSCF at the called side sends a call response message to the P-CSCF at the calling side.

Step 209: The P-CSCF at the calling side returns the key generated by itself to the calling terminal through a call response message.

In this step, if the call response message is a 183 message, the P-CSCF at the calling side may carry the key x generated in advance in the k field of the SDP and send it to the calling terminal. In addition, if the declaration mechanism of RFC 4568 is used before, the key can be carried in the inline field.

If the call response message is a 200OK message, a SIP header field may be extended in the 200OK message to carry the key x. For example: to extend a Media-Key header field, its format is as follows:

Media-Key:<Key>

Among them, Key represents the generated key. In this way, the key x can be returned to the calling terminal by using 200OK.

Step 210: The generating key unit in the P-CSCF at the called side generates a key y according to the encryption capability information of the called terminal.

Step 211: The P-CSCF at the called side initiates a resource reservation process, and sends a message carrying the key y to the RACS at the called side during the resource reservation process.

Step 212: The RACS at the called side sends the key y to the MP at the called side.

Here, the steps 211 to 212 are that the P-CSCF at the called side sends the generated key process resource reservation process to the MP at the called side. The method is the same as steps 204 to 205, and will not be described in detail here. .

When the P-CSCF on the calling side receives the call response message, it executes the subsequent call process, that is, executes steps 208 to 209; while generating and issuing a key, that is, executes steps 210 to 212. That is to say, on the called side, the subsequent call process and key generation and delivery are also two parallel processes, and there is no strict sequence in time.

Steps 213 to 214: the calling terminal sends a confirmation message to the called P-CSCF through the calling P-CSCF.

Step 215: The P-CSCF at the called side sends the generated key y to the called terminal through a confirmation message.

In this embodiment, the P-CSCF at the called side sends the key y to the called terminal through a confirmation message, that is, a PRACK message or an ACK message. If the called terminal returned a 183 message before, the calling terminal needs to send a PRACK message to the called terminal, and the P-CSCF at the called side can carry the key y in the k field of the SDP in the PRACK message; if the called terminal If the 200OK message was returned before, the calling terminal needs to send an ACK message to the called terminal, and the P-CSCF at the called side can carry the key y in the extended Media-Key field in the ACK message.

Step 216: the calling terminal, the calling MP, the called MP and the called terminal transmit the media stream by using the keys obtained respectively.

In practical applications, when the calling terminal calls the called terminal, the interactive message or signaling should be transmitted through the signaling link, but after the call is successful, the media stream data should be transmitted through the data link, that is, through the calling terminal , the MP on the calling side, the MP on the called side, and the called terminal.

The method of transmitting the media stream is as follows:

When the media stream is transmitted from the calling terminal to the called terminal, the calling terminal uses the obtained key x to encrypt the media stream, and transmits the encrypted media stream to the MP on the calling side; the MP on the calling side uses the obtained key x key x to decrypt the media stream, and then transmit the decrypted media stream to the called MP; Ask the terminal to use the obtained key y to decrypt the media stream.

When the media stream is transmitted from the called terminal to the calling terminal, the called terminal uses the key y to encrypt the media stream, and transmits the encrypted media stream to the MP on the called side; the MP on the called side uses the key y to encrypt the media stream The stream is decrypted, and then the decrypted media stream is transmitted to the calling side MP; the calling side MP uses the key x to encrypt the media stream, and transmits the encrypted media stream to the calling terminal; the calling terminal uses the key x x decrypts the media stream.

That is to say, the media stream is encrypted with the key x on the calling side for secure transmission, and encrypted with the key y at the called side for secure transmission.

In addition, in practical applications, if the called terminal returns a 183 message, the calling terminal also needs to send an information update message, ie, an UPDATE message, to the called terminal after sending the PRACK message. At this time, the P-CSCF at the called side may not send the key y to the called terminal through a PACK message, but send the key y to the called terminal through an UPDATE message.

In a word, what needs to be emphasized in the present invention is that the key generation unit obtains the encryption capability information of the terminal during the call process, generates a key according to the encryption capability information, and then sends the key to the terminal and the media stream bearing device respectively. As for which message in the call process to obtain the encryption capability information, which message to send the key to the terminal, and how to send the key to the media stream bearing device can be determined by the user applying the solution of the present invention , which will not be repeated here.

The embodiment of the present invention is described by taking a network containing an IP Multimedia Subsystem (IMS) as an example, and the signaling link in the IMS network can provide security guarantee. In practical applications, the method of the present invention can also be applied to other types of networks, such as the next generation network based on softswitch, the method is similar to the present invention, and will not be listed here.

Aiming at the method for securely transmitting media streams, the present invention also proposes a system for securely transmitting media streams. FIG. 3 is a schematic diagram of a basic structure of a system for securely transmitting media streams. As shown in FIG. 3 , the system includes: a terminal 301 , a media stream bearing device 302 and a key generation unit 303 .

Wherein, the terminal 301 is configured to send its own encryption capability information to the key generation unit 303, obtain the key and be responsible for the media stream according to the key.

The media stream bearing device 302 is configured to receive the key generated by the key generation unit 303, and is responsible for transmitting the media stream according to the key.

The key generating unit 303 is configured to receive the encryption capability information input by the terminal 301, generate a key, and send the generated key to the terminal 301 and the media stream bearing device 302 respectively.

Here, the terminal 301 may be a calling terminal or a called terminal; the media stream bearing device 302 may be the media stream bearing device on the calling side or the media stream bearing device on the called side; the key generating unit 303 It can be a key generation unit at the calling side or a key generation unit at the called side, and the key generation unit can be a functional unit in the P-CSCF or an independent server.

In order to better illustrate the structure and functions of the system of the present invention, a system embodiment is used for a detailed description below.

System embodiment

In this embodiment, the key generation unit is a functional unit in the P-CSCF, the media stream bearing device is an MP, and the key is obtained through RACS.

Fig. 4 is a schematic diagram of the system structure of the present invention. As shown in Figure 4, this embodiment includes calling terminal 401, calling side P-CSCF402, calling side RACS403, calling side MP404, called terminal 405, called side P-CSCF406, called side RACS407, called Call side MP408.

The calling terminal 401 and the called terminal 405 respectively send their own encryption capability information to the calling side P-CSCF 402 and the called side P-CSCF 406 to obtain a key and be responsible for transmitting media streams according to the key.

The P-CSCF402 on the calling side and the P-CSCF406 on the called side generate keys respectively, and send the generated keys to the RACS403 on the calling side and the RACS407 on the called side respectively.

The calling side RACS403 and called side RACS407 forward the key generated by the calling side P-CSCF402 and the called side P-CSCF406 to the calling side MP404 and called side MP408 respectively.

The MP404 on the calling side and the MP408 on the called side receive keys from the RACS403 on the calling side and the RACS407 on the called side respectively, and are responsible for transmitting media streams according to the keys.

When the calling terminal 401 initiates a call, the calling terminal 401 sends a call request message carrying its own encryption capability information to the calling side P-CSCF402; the calling side P-CSCF402 sends the call request message through the called side P-CSCF406 To the called terminal 405, at the same time, the P-CSCF402 of the calling side generates a key according to the encryption capability information of the calling terminal 401, and sends the key to the calling side MP404 through the calling side RACS403; when the called terminal 405 receives When calling a request message, return a call response message carrying its own encryption capability information to the called side P-CSCF406; the called side P-CSCF406 returns the call response message to the calling side P-CSCF402, and the calling side P-CSCF402 then Carry the pre-generated key in the call response message and return it to the calling terminal 401. At the same time, the P-CSCF406 on the called side generates a key according to the encryption capability information of the called terminal 405, and sends the key to the The calling side MP408; thereafter, the calling terminal 401, the calling side MP404, the called side RACS407, and the called terminal 405 use the key to transmit the media stream.

By applying the scheme of the present invention, the terminal and the media stream bearing device can obtain the key generated by the key generation unit, without the need for relatively complicated processes such as certificate management and clock synchronization, and can easily realize secure transmission of the media stream; the calling side The unencrypted media stream is transmitted between the media stream bearing device and the media stream bearing device on the called side, which can meet the actual needs of legal agencies to implement legal interception without a key; in addition, because the calling side The generation of the key is independent from the called side, no negotiation is required, and the execution of the call process may not be affected when the key is generated and issued.

To sum up, the above are only preferred embodiments of the present invention, and are not intended to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (12)

1. the method for a safely transmitting media stream is characterized in that, sets in advance the key generation unit, and this method may further comprise the steps:

A, key generation unit obtain the cryptographic capabilities information of terminal in call flow, and generate the key that is used for Media Stream according to described cryptographic capabilities information;

B, again the key that generates is sent to terminal respectively and is used for media stream bearing equipment;

The cipher key delivery Media Stream that C, terminal and media stream bearing equipment utilization are obtained.

2. method according to claim 1, it is characterized in that, described key generation unit is the functional unit of Calling Side call conversation control function entity CSCF, and described terminal is a calling terminal, and then the described key generation unit of the steps A method of obtaining cryptographic capabilities information is specially:

Calling terminal makes a call, and the call request message that carries the self-encryption ability information is sent to Calling Side CSCF, and Calling Side CSCF obtains the cryptographic capabilities information of calling terminal from call request message.

3. method according to claim 2 is characterized in that, the cryptographic capabilities information-bearing of described calling terminal is in the Session Description Protocol SDP of call request message; The session initiation protocol SIP caller attributes that perhaps is carried on call request message receives to be consulted in the Accept-contact header field; Perhaps be carried in the call request message in the SIP extension negotiation territory, described SIP extension negotiation territory is for supporting the supported territory; Perhaps be carried in the call request message in the defined field of exposure draft RFC 4568 standards.

4. method according to claim 2 is characterized in that, the described method that key is sent to calling terminal of step B is:

When Calling Side CSCF receives call message from terminal called, the key that generates in advance is carried on described call message sends to calling terminal.

5. method according to claim 2 is characterized in that, described media stream bearing equipment is Calling Side Media proxy MP, and the described method that key is sent to Calling Side MP of step B is:

The message that Calling Side CSCF will carry key sends to Calling Side resource and access control subsystem RACS, and Calling Side RACS sends to key Calling Side MP again.

6. method according to claim 2 is characterized in that, described step C is specially:

When Media Stream when calling terminal is transferred to terminal called, the key that the calling terminal utilization is obtained is encrypted Media Stream, give Calling Side MP with the encrypted media flow transmission, Calling Side MP utilizes the key that obtains that Media Stream is decrypted again, and the media flow transmission after will deciphering is then gone out; And/or

When Media Stream when terminal called is transferred to calling terminal, Calling Side MP utilizes the key that obtains to encrypt from the Media Stream of terminal called, gives calling terminal with the encrypted media flow transmission, calling terminal utilizes the key that obtains that Media Stream is decrypted again.

7. method according to claim 1 is characterized in that, described key generation unit is the functional unit among the callee side CSCF, and described terminal is a terminal called, and then the described method of obtaining cryptographic capabilities information of steps A is specially:

Terminal called receives call request message from calling terminal by callee side CSCF, the call message that carries terminal called self-encryption ability information is returned to callee side CSCF, and callee side CSCF obtains the cryptographic capabilities information of terminal called from call message.

8. method according to claim 7 is characterized in that, the described method that key is sent to terminal called of step B is:

When callee side CSCF receives from calling terminal when calling out relevant message, the key that generates in advance is carried on the described message relevant with calling sends to terminal called.

9. method according to claim 7 is characterized in that, described media stream bearing equipment is callee side MP, and the described method that key is sent to callee side MP of step B is:

The message that callee side CSCF will carry key sends to callee side RACS, and callee side RACS sends to key callee side MP again.

10. method according to claim 7 is characterized in that, described step C is specially:

When Media Stream when calling terminal is transferred to terminal called, callee side MP utilizes the key that obtains to encrypt from the Media Stream of caller terminal, gives terminal called with the encrypted media flow transmission, terminal called utilizes the key that obtains that Media Stream is decrypted again; And/or

When Media Stream when terminal called is transferred to calling terminal, the key that the terminal called utilization is obtained is encrypted Media Stream, give callee side MP with the encrypted media flow transmission, callee side MP utilizes the key that obtains that Media Stream is decrypted again, and the media flow transmission after will deciphering is then gone out.

11. the system of a safely transmitting media stream comprises terminal, media stream bearing equipment, it is characterized in that this system also comprises the key generation unit;

Described terminal is used for the self-encryption ability information is sent to the key generation unit, obtains key, is responsible for media stream according to key;

Described media stream bearing equipment is used to receive the key that is generated by the key generation unit, is responsible for media stream according to key;

Described key generation unit is used for the cryptographic capabilities information that receiving terminal is imported, and generates key, and the key that generates is sent to terminal and media stream bearing equipment respectively.

12. system according to claim 11 is characterized in that, described key generation unit is the functional unit among the P-CSCF, and described media stream bearing equipment is MP, and this system further comprises:

RACS is used for receiving the key that is generated by P-CSCF key generation unit, and key is transmitted to MP.

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