The generation transmission synchronization method of digital cellular mobile communication systems initial vector
Technical field
The present invention relates to a kind of generation, transmission and method for synchronous of digital cellular mobile communication systems digital encryption initial vector.
Background technology
In the digital encryption communication system, realize the change at random of each cryptosync cryptographic algorithm initial vector, have important function for improving security of communication system.The numeral of existing digital cellular mobile communication systems transmission generally adopts frame peculation method to realize encrypting generation, the transmission and synchronous of initial vector.Do to encrypt initial vector with number of frames, exist the randomness of encrypting initial vector bad, encrypt problems such as the initial vector sample is less; And frame peculation method is diverted particular frame transmission initial vector, and transport service is had the damage of moving, and also brings the reliable transmission problem of self simultaneously.
Summary of the invention
The objective of the invention is to: provide a kind of not damage of transport service, the initial vector sample number is big, the efficient height, fail safe is good, can solve digital cellular mobile communication systems preferably and encrypt problems such as the big complexity synchronously of initial vector transport overhead, realize generation, transmission and the synchronous method of digital encryption initial vector based on link layer sliding window round number and Frame sequence number.
The objective of the invention is to realize by the enforcement following technical proposals:
1, the generation of initial vector
Add the round of link layer transfer of data sliding window number as initial vector with link layer Frame sequence number.The sequence number field of link layer Frame is more than or equal to 10 bits, the reciprocity Logical Link Entity of portable terminal and base station, can keep the sliding window that a sequence number wheel that is consistent changes, the round of this sliding window is more than or equal to 22 bits, and this round number and Frame sequence number field be common forms the initial vector more than or equal to the encrypted message key of 32 bits.
2, the transmission of initial vector
The Frame sequence number that constitutes the key initial vector is the part of Frame, transmits with Frame as the part of data frame head.Frame is intercepted and captured, and does not have the synchronous round of sliding window number, does not influence the fail safe of whole initial vector.The sliding window round that constitutes initial vector another part number not be used in aerial transmission, only is kept at synchronously in portable terminal and the base station transceiver respectively.Each like this message key only needs a transmission part aloft, has both reduced transport overhead, has also strengthened fail safe.
3, initial vector is synchronous
Initial vector synchronously just round number synchronously.The initial value of two reverse rounds number of the logic control entity of equity can be determined by link management information in the process that the data logical links is set up.Later on round number is got back to from 1023 sending sequence number of the each Frame of transmit leg and was added 1 at 0 o'clock, and the recipient can be according to the position of current reception sliding window and the sequence number field of receiving data frames, judges the round number of each data of reception.When mobile terminal skip zone switched, to the current round parameter of old base station transceiver application, old base station transceiver number was issued new base station transceiver with round to new base station transceiver, to keep initial vector synchronous by base station controller.
The invention has the advantages that: owing to adopt link layer sliding window wheel sequence number addend according to frame number, as digital cellular mobile communication systems digital encryption initial vector, constitute the sliding window round number not transmission aloft of this initial vector, only be kept in portable terminal and the base station transceiver respectively synchronously, therefore avoided existing employing frame to divert the insecurity that mode is transmitted initial vector in the air, also improved simultaneously the utilization ratio of system channel, guaranteed the transport service not damaged; On the other hand, this method is simple, without special installation or device, avoided taking the situation of huge resource as other key distribution management system, reliability, easy implementation and the ease for operation that improves the digital cellular mobile communication systems encryption is of practical significance.
Description of drawings
Fig. 1 is the LAS-PDMA traffic model
Fig. 2 is the protocol hierarchy model
Fig. 3 is a sliding window round variation diagram
Mark among the figure: IP is the internet, upper strata, and RLC is the logic link control device, and LLE is the link encryption layer, and 1 is the initial round of sliding window number, and 2 are sliding window skew round number.
Embodiment
The simple communication model of novel 3G (Third Generation) Moblie technology LAS-PDMA as shown in Figure 1.Between portable terminal and base station transceiver, realized aerial encryption, encrypted level and be positioned at logical link control layer that Fig. 2 has provided concrete protocol hierarchy model.RLC among Fig. 2 promptly is a logical link control layer, and LLE is the link encryption sublayer.The link encryption sublayer is that the function that airlink is encrypted realizes entity.In the LAS-PDMA system to real time business as speech, image, multimedia adopts the cipher mode of stream cipher.Realize the data encryption of stream cipher mode, will relate to the problem of cryptosync.The method of synchronization can adopt frame number to add the mode of round number.
Logical link control layer data frame format such as following table:
Mobile terminal address 8bit | Head is known 1bit | Type 5bit | Numbering 10bit | Application (No.1 CRC) 8bit | Data | ?CRC ?16bit |
Wherein number field is 0 to 1023 frame number.
When the portable terminal access base station, both sides number have carried out initial synchronisation at the round of sliding window, number will not remain unchanged as long as link does not interrupt this round.Fig. 3 has provided the variation of sliding window round in the communication number, and the sliding window initial round when mark 1 begins for communication number for example is 0X2001, and mark 2 number for example be 0X2004 for certain sliding window skew round constantly in the communication, and round number is total to 22bits.Carry out when having only the first access base station of portable terminal after this aloft not transmitting synchronously.Portable terminal and base station adopt same strategy to be offset, and the message key structure is exactly like this:
Frame number 10bits+ round 22bits
If certain frame number is the frame of the 0X200 of 16 systems, this moment, round number was 0X2001, and its key is exactly 0X10002001; The next frame frame number is 0X201, round 0X2001, and its key is exactly 0X10402001.
When portable terminal between the base station during handover, round number is transmitted between base station controller, portable terminal can be easy to realize that the initial vector of encrypted message key is synchronous after switching.
The sample of this method message key is very big, and because the skew rule of round number is underground, can adopt different skew rules between different mobile terminal and the base station, and its fail safe is high.Even if the key of this frame is intercepted and captured, do not influence the fail safe of next frame yet.The key synchronization dependent frame is synchronous, does not have independent synchronizing process, implements simply, does not have unnecessary expense for the switching of cellular mobile communication, helps the real-time transmission of real time business.Its superiority is conspicuous.