Patent Document

This application is a continuation of and claims priority to U.S. application Ser. No. 10/885,115, filed on Jul. 7, 2004, which claims priority from U.S. Provisional Patent Application No. 60/484,656 filed on Jul. 7, 2003. The entire contents of the U.S. patent application Ser. No. 10/885,115 are hereby incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a method and apparatus for providing an adaptable security level in an electronic communication. 
     2. Description of the Prior Art 
     In electronic communications, it is often necessary to prevent an eavesdropper from intercepting message. It is also desirable to have an indication of the authenticity of a message, that is a verifiable identification of the sender. These goals are usually achieved through the use of cryptography. Private key cryptography requires sharing a secret key prior to initiating communications. Public key cryptography is generally preferred as it does not require such a shared secret key. Instead, each correspondent has a key pair including a private key and a public key. The public key may be provided by any convenient means, and does not need to be kept secret. 
     There are many variations in cryptographic algorithms, and various parameters that determine the precise implementation. In standards for wireless communications, it has been customary to set these parameters in advance for each frame type. However, this approach limits the flexibility of the parameters. 
     When one device is communicating with several other devices, it will often need to establish separate parameters for each communication. 
     It is an object of the present invention to obviate or mitigate the above disadvantages. 
     SUMMARY OF THE INVENTION 
     In accordance with one aspect, there is provided a method and cryptographic unit for communicating between a sender and at least one recipient in a data communication system comprising the sender assembling a packet stream comprising a plurality of frames, each frame having a header and data; determining individually for each of the frames, a security level based on known security requirements. Thereby allowing different frames to have different security to adapt to the nature of respective frames; including a corresponding indication of the security level in respective ones of the frames; and providing the frames for cryptographically processing each frame according to the corresponding indication of the security level. 
     In accordance with another aspect, there is provided a method and cryptographic unit for a recipient processing communications received from a sender in a data communication system comprising the steps of: receiving from the sender, a packet comprising a plurality of frames, each frame having a header and data, wherein respective ones of the frames includes a corresponding indication of a security level determined individually by the sender for each of the frames based on known security requirements, such that different frames are capable of having different security to adapt to each of the frames; and for each frame received, examining the indication of security level and rejecting the frame if it does not attain a minimum level. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       These and other features of the preferred embodiments of the invention will become more apparent in the following detailed description in which reference is made to the appended drawings wherein: 
         FIG. 1  is a schematic representation of a communication system; 
         FIG. 2  is a schematic representation of an information frame exchanged in the communication system of  FIG. 1 ; 
         FIG. 3  is a schematic representation of a frame control portion of the frame of  FIG. 2 ; 
         FIG. 4  is a schematic representation of a method performed by a sender in  FIG. 1 ; 
         FIG. 5  is a schematic representation of a method performed by a recipient in  FIG. 1 . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to  FIG. 1 , a communication system  10  includes a pair of correspondents  12 ,  14  connected by a communication link  16 . Each correspondent  12 ,  14  includes a respective cryptographic unit  18 ,  20 . 
     Each correspondent  12 ,  14  can include a processor  22 ,  24 . Each processor may be coupled to a display and to user input devices, such as a keyboard, mouse, or other suitable devices. If the display is touch sensitive, then the display itself can be employed as the user input device. A computer readable storage medium is coupled to each processor  22 ,  24  for providing instructions to the processor  22 ,  24  to instruct and/or configure processor  22 ,  24  to perform steps or algorithms related to the operation of each correspondent  12 ,  14 , as further explained below. The computer readable medium can include hardware and/or software such as, by way of example only, magnetic disks, magnetic tape, optically readable medium such as CD ROM&#39;s, and semi-conductor memory such as PCMCIA cards. In each case, the medium may take the form of a portable item such as a small disk, floppy diskette, cassette, or it may take the form of a relatively large or immobile item such as hard disk drive, solid state memory card, or RAM provided in a support system. It should be noted that the above listed example mediums can be used either alone or in combination. 
     In order to transfer data between the correspondents  12 ,  14 , a packet stream  30  is assembled at one of the correspondents in accordance with a defined protocol. The packet stream  30  is shown schematically in  FIG. 2  and is composed of one or more frames  31 , each of which has a header  32  and data  34 . In some protocols, the packet may itself be organised as a frame with a header  32   a  and the data  34   a  consisting of a collection of individual frames. The header  32  is made up of a string of bits and contains control information at specified locations within the bit stream. 
     Included in each of the headers  34  are security control bits  33 , that includes a security mode bit  35  and integrity level bits  36 , 37 . 
     In this embodiment, security mode bit  35  is used to indicate whether encryption is on or off. Security bits  36  and  37  together are used to indicate which of four integrity levels, such as 0, 32, 64, or 128 bit key size is utilised. The security mode bit may be used to indicate alternative modes of operation such as authentication, and the number of bits may be increased to accommodate different combinations. It will be recognized that providing security bits in each frame  31  of the stream  30  allows the security level to be on a frame-by-frame basis rather than on the basis of a pair of correspondents, therefore providing greater flexibility in organizing communications. 
     In order to provide security, certain minimum security levels may be used. These levels should be decided upon among all of the correspondents through an agreed-upon rule. This rule may be either static or dynamic. 
     In operation, the correspondent  12  performs the steps shown in  FIG. 4  by the numeral  100  to send information to the correspondent  14 . First, the correspondent  12  prepares data and a header at step  102 . Then it selects the security level at step  104 . The security level is determined by considering the minimum security level required by the recipient, the nature of the recipient, and the kind of data being transmitted. If the security level includes encryption, then the correspondent  12  encrypts the data at step  106 . If the security level includes authentication, then the correspondent  12  signs the data at step  108 . Then the correspondent  12  includes bits indicating the security mode and security level in the frame control at step  110 . The correspondent  12  then sends the frame to the correspondent  14 . 
     Upon receiving the frame, the correspondent  14  performs the steps shown in  FIG. 5  by the numeral  120 . The correspondent  14  first receives the frame at step  122 . It then extracts the security bits at step  124 . If the security mode bits  35 _indicate encryption, then the correspondent  14  decrypts the data at step  126 . If the security bits indicate authentication, then the correspondent  14  verifies the signature at step  126 . Finally, the correspondent  14  checks the security level to ensure it meets predetermined minimum requirements. If either the encryption or authentication fails, or if the security level does not meet the minimum requirements, then the correspondent  14  rejects the message. 
     It will be recognized that providing security bits and an adjustable security level provides flexibility in protecting each frame of the communication. It is therefore possible for the sender to decide which frames should be encrypted but not authenticated. Since authentication typically increases the length of a message, this provides a savings in constrained environments when bandwidth is at a premium. 
     In a further embodiment, the correspondent  12  wishes to send the same message to multiple recipients  14  with varying minimum security requirements. In this case, the correspondent  12  chooses a security level high enough to meet all of the requirements. The correspondent  12  then proceeds as in  FIG. 4  to assemble and send a message with the security level. The message will be accepted by each recipient since it meets each of their minimum requirements. It will be recognized that this embodiment provides greater efficiency than separately dealing with each recipient&#39;s requirements. 
     In another embodiment, a different number of security bits are used. The actual number of bits is not limited to any one value, but rather may be predetermined for any given application. The security bits should indicate the algorithm parameters. They may be used to determine the length of a key as 40 bits or 128 bits, the version of a key to be used or any other parameters of the encryption system. 
     Although the invention has been described with reference to certain specific embodiments, various modifications thereof will be apparent to those skilled in the art without departing from the spirit and scope of the invention as outlined in the claims appended hereto.

Technology Category: 5