Abstract:
The present invention provides a method for performing an inversion and multiply in a single operation as a polynomial divide operation. As a result, the invention reduces the number of mathematical operations needed to perform point doubling and point addition operations. An elliptic curve cryptosystem using the present invention can be made to operate more efficiently using the present invention. An elliptic curve crypto-accelerator can be implemented using the present invention to dramatically enhance the performance of the elliptic curve cryptosystem. The invention uses five registers A, B, U, V, and M, to accomplish a polynomial divide operation. Four registers A, B, U, and V are initialized with values so that the registers maintain a number of invariant relationships. The registers store initial values a(t)=x(t), u(t)=y(t), b(t)=prime(t), and v(t)=0. Here the polynomials in registers A, U, B, and V are denoted as a(t), u(t), b(t), and v(t), respectively. Register M stores the irreducible polynomial prime(t). By applying a series of invariant operations to the registers, the register values are systematically reduced until registers A and B have a value of one. At that point, register U stores a value which represents y(t)/x(t) mod prime(t), solving the polynomial division.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to modular polynomial divisions. 
     Portions of the disclosure of this patent document contain material that is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure as it appears in the Patent and Trademark Office file or records, but otherwise reserves all copyright rights whatsoever. 
     2. Background Art 
     Computer systems are useful for performing mathematical operations (add, subtract, multiply, divide) on operands. Often the operands are polynomials. A polynomial is a mathematical expression of one or more algebraic terms each of which consists of a constant multiplied by one or more variables raised to a nonnegative integral power (e.g. a+bx+cx 2 ). The task of performing mathematical operations on polynomial operands is difficult in the sense that it is not simply a matter of multiplying or dividing two simple numbers. There are a number of schemes that provide methods for performing mathematical operations on polynomials. However, there are situations for which no suitable schemes have been provided. 
     One situation that requires the manipulation of polynomials is the encryption and decryption of data in a cryptosystem and digital signatures for verification of the sender. A cryptosystem is a system for sending a message from a sender to a receiver over a medium so that the message is “secure”, that is, so that only the intended receiver can recover the message. A cryptosystem converts a message, referred to as “plaintext” into an encrypted format, known as “ciphertext.” The encryption is accomplished by manipulating or transforming the message using a “cipher key” or keys. The receiver “decrypts” the message, that is, converts it from ciphertext to plaintext, by reversing the manipulation or transformation process using the cipher key or keys. So long as only the sender and receiver have knowledge of the cipher key, such an encrypted transmission is secure. 
     A digital signature is a bit-stream generated by a cryptosystem. It is attached to a message such that a receiver of the message can verify with the bit-stream and be assured that the message was indeed originated from the sender it claims to be. A “classical” cryptosystem is a cryptosystem in which the enciphering information can be used to determine the deciphering information. To provide security, a classical cryptosystem requires that the enciphering key be kept secret and provided to users of the system over secure channels. Secure channels, such as secret couriers, secure telephone transmission lines, or the like, are often impractical and expensive. 
     A system that eliminates the difficulties of exchanging a secure enciphering key is known as “public key encryption.” By definition, a public key cryptosystem has the property that someone who knows only how to encipher a message cannot use the enciphering key to find the deciphering key without a prohibitively lengthy computation. An enciphering function is chosen so that once an enciphering key is known, the enciphering function is relatively easy to compute. However, the inverse of the encrypting transformation function is difficult, or computationally infeasible, to compute. Such a function is referred to as a “one way function” or as a “trap door function.” In a public key cryptosystem, certain information relating to the keys is public. This information can be, and often is, published or transmitted in a non-secure manner. Also, certain information relating to the keys is private. This information may be distributed over a secure channel to protect its privacy, (or may be created by a local user to ensure privacy). Some of the cryptosystems that have been developed include the RSA system, the Massey-Omura system, and the El Gamal system. 
     Elliptic Curves 
     Another form of public key cryptosystem is referred to as an “elliptic curve” cryptosystem. An elliptic curve cryptosystem is based on points on an elliptic curve E defined over a finite field F. Elliptic curve cryptosystems rely for security on the difficulty in solving the discrete logarithm problem. An advantage of an elliptic curve cryptosystem is there is more flexibility in choosing an elliptic curve than in choosing a finite field. Nevertheless, elliptic curve cryptosystems have not been widely used in computer-based public key exchange systems due to their late discovery and the mathematical complexity involved. Elliptic curve cryptosystems are described in “A Course in Number Theory and Cryptography” (Koblitz, 1987, Springer-Verlag, N.Y.). 
     In practice an Elliptic Curve group over Fields F( 2 m) is formed by choosing a pair of a and b coefficients, which are elements within F( 2 m). The group consists of a finite set of points P(x,y) which satisfy the elliptic curve equation 
     
       
         
           y 
           2 
           +xy=x 
           3 
           +ax 
           2 
           +b 
         
       
     
     together with a point at infinity, O. The coordinates of the point, x andy, are elements of F( 2 m) represented in m-bit strings. Since F( 2 m) operates on bit strings and the field has a characteristic 2, computers can perform arithmetic in this field very efficiently. The arithmetic in F( 2 m) can be defined in either a standard basis representation or optimal normal basis representation. This description uses the standard basis representations for purposes of discussion. All elliptic curve point coordinates are represented as polynomials with binary coefficients. 
     The Elliptic Curve Cryptosystem relies upon the difficulty of the Elliptic Curve Discrete Logarithm Problem (ECDLP) to provide its effectiveness as a cryptosystem. Using multiplicative notation, the problem can be described as: given points P and Q in the group, find a number k such that P K =Q; where k is called the discrete logarithm of Q to the base P. Using additive notation, the problem becomes: given two points P and Q in the group, find a number k such that kP=Q. 
     In an Elliptic Curve Cryptosystem, the large integer k is kept private and is often referred to as the secret key. The point Q together with the base point P are made public and are referred to as the public key. The security of the system, thus, relies upon the difficulty of deriving the secret k, knowing the public points P and Q. The main factor that determines the security strength of such a system is the size of its underlying finite field. In a real cryptographic application, the underlying field is made so large that it is computationally infeasible to determine k in a straight forward way by computing all the multiples of P until Q is found. 
     The core of the elliptic curve geometric arithmetic is an operation called scalar multiplication which computes kP by adding together k copies of the point P. The scalar multiplication is performed through a combination of point-doubling and point-addition operations. The point-addition operation adds two distinct points together and the point-doubling operation adds two copies of a point together. To compute, for example, 11P=(2*(2*(2P)))+2P=P, it would take 3 point-doublings and 2 point-additions. 
     Point-doubling and point-addition calculations require special operations when dealing with polynomial operands. Algebraic schemes for accomplishing these operations are illustrated below in Table 1. 
     
       
         
               
               
               
             
           
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                 Point addition: R = P + Q 
                 Point Doubling: R = 2P 
               
               
                   
                   
               
             
             
               
                   
                 S = (y P  − y Q )*(1/(x P  + x Q )) 
                 S = x P  + y P *(1/x P ) 
               
               
                   
                 x R  = s 2  + s + a + x P  + x Q   
                 x R  = s 2  + s + a 
               
               
                   
                 y R  = s*(x P  + x R ) + x R  + y P   
                 y R  = x P   2  + (s + 1)*x R   
               
               
                   
                 If Q = −P, R = P + (−P) = O, infinity 
                 If x P  = O, 
               
               
                   
                   
                 then R = 2 P = O, infinity 
               
               
                   
                   
               
             
          
         
       
     
     The two equations for S in the table are called the slope-equations. Computation of a slope equation requires one modular polynomial inversion ( 1 /X mod M) where M is an irreducible polynomial and one modular polynomial multiplication (*Y mod M). Because the operands are polynomials, these operations are typically done back-to-back as two separate operations. There exist algorithms and solutions to calculate the modular inversion  1 /X mod M and the modular multiplication *Y mod M. After the result of the modular inversion is calculated, the multiplication *Y mod M is performed. Of course, algebraically ( 1 /X*Y) mod M is the same as Y/X mod M. However, there is currently no technique for calculating modular Y/X in one operation when the operands are polynomial functions. These two field operations, the inversion and the multiply, are expensive computationally because they require extensive CPU cycles for the manipulation of two large polynomials modular a large irreducible polynomial. Today, it is commonly accepted that a point-doubling and point-addition operation each requires one inversion, two multiplies, a square, and several additions. To date there are techniques to compute modular inversions, and techniques to trade expensive inversions for multiplies by performing the operations in projective coordinates. There have been no efficient hardware oriented techniques suggested to compute a modular division directly which can be used to perform point doubling and point addition operations. 
     SUMMARY OF THE INVENTION 
     The present invention provides a method for performing an inversion and multiply in a single operation as a polynomial divide operation. As a result, the invention reduces the number of mathematical operations needed to perform point doubling and point addition operations. An elliptic curve cryptosystem using the present invention can be made to operate more efficiently using the present invention. An elliptic curve crypto-accelerator can be implemented using the present invention to dramatically enhance the performance of the elliptic curve cryptosystem. 
     The invention uses five registers A, B, U, V, and M, to accomplish a polynomial divide operation. Four registers A, B, U, and V are initialized with values so that the registers maintain a number of invariant relationships. The registers store initial values a(t)=x(t), u(t)=y(t), b(t)=prime(t), and v(t)=0. Here the polynomials in registers A, U, B, and V are denoted as a(t), u(t), b(t), and v(t), respectively. Register M stores the irreducible polynomial prime(t). By applying a series of invariant operations to the registers, the register values are systematically reduced until registers A and B have a value of one. At that point, register U stores a value which represents y(t)/x(t) mod prime(t), solving the polynomial division. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other features, aspects and advantages of the present invention will become better understood with regard to the following description, appended claims and accompanying drawings where: 
     FIG. 1 is a flow diagram illustrating the operation of the present invention. 
     FIG. 2 is a flow diagram illustrating an iterative implementation of the present invention. 
     FIG. 3 illustrates an execution environment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The invention is a method for efficient modular polynomial divisions. In the following description, numerous specific details are set forth to provide a more thorough description of embodiments of the invention. It is apparent, however, to one skilled in the art, that the invention may be practiced without these specific details. In other instances, well known features have not been described in detail so as not to obscure the invention. 
     The invention provides a system for performing polynomial divides so that a polynomial inversion and multiply can be accomplished in one operation at the same computational cost as a polynomial inversion. The invention is described in connection with example operations from an elliptic curve cryptosystem. 
     Consider the division of two polynomials in the Fields F( 2 m). The invention combines a multiplication with an inversion process. Thus, the slope equation s=x p +y p /x p  can be computed using one division operation at the cost of an inversion, and no multiplies: 
     
       
         
               
               
               
             
           
               
                   
                   
               
               
                   
                 Point addition: 
                 Point doubling: 
               
               
                   
                   
               
             
             
               
                   
                 s = (y P  − y Q )/(x P  + x Q ) 
                 s = x P  y P /x P   
               
               
                   
                   
               
             
          
         
       
     
     The invention computes the modular division of two polynomials y(t)/x(t) modulo prime(t). 
     Here, the function, y(t), is the numerator and the function, x(t), is the denominator, which are the two polynomial input functions to the polynomial-divide algorithm. The polynomial, prime(t), is the irreducible polynomial of the field. 
     The invention is implemented in a computer system by using five registers, A, B, U, V, and M. The fifth register M that holds the irreducible polynomial prime(t) is not shown here.                           
     A bit-string in a register corresponds to a polynomial. For example, a bit-string of (1011000101) in register B indicates that b(t)=t 9 +t 7 +t 6 +t 2 +1. The big-string representation and the polynomial representation are inter-changeable. The invention uses a(t), b(t), u(t), and v(t) to refer to the polynomials in the A, B, U, and V registers, respectively. 
     The four registers are initialized with the values: 
     a(t)=x(t), u(t)=y(t), b(t)=prime(t), and v(t)=0, 
     such that the polynomials in the registers satisfy the following invariant relationships: 
     
       
           a ( t )* y ( t )= u ( t )* x ( t ) mod prime( t )  (1) 
       
     
     
       
           b ( t )* y ( t )= v ( t )* x ( t ) mod prime( t )  (2) 
       
     
     One should note that b(t) is congruent to zero modular the prime polynomial. 
     Throughout the division process, the invention monolithically and iteratively reduces the contents in register A and B down to one by applying a combination of the following 4 invariant operations which guarantee the invariant relationship (1) and (2) throughout the entire process: 
     Operation 1: Right-shift-Register-A-and-U: 
     a(t)=a(t)&gt;&gt;1; 
     If (u 0 ==1) u(t)=u(t)+prime(t); 
     u(t)=u(t)&gt;&gt;1; 
     Operation 2: Right-shift-Register-B-and-V: 
     b(t)=b(t)&gt;&gt;1; 
     If (v 0 ==1) v(t)=v(t)+prime(t); 
     v(t)=v(t)&gt;&gt;1; 
     Operation 3: Add-Register-A-to-B-and-U-to-V: 
     If (b 0 ==1): b(t)=b(t)+a(t) and v(t)=v(t)+u(t) 
     Operation 4: Add-Register-B-to-A-and-V-to-U: 
     If (a 0 ==1): a (t)=a(t)+b(t) and u(t)=u(t)+v(t); 
     The notations a 0 , b 0 , u 0 , and v 0  indicate the least-significant-bit of each register, respectively. 
     The goal is to reduce registers A and B to values of one. This is accomplished by applying the four above operations when possible using the following rules. 
     Rule #1: Apply Operation 1 whenever the least significant bit of Register A is zero, i.e. a=0, to reduce the polynomial a(t); 
     Rule #2: Apply Operation 2 whenever the least significant bit of Register B is zero, i.e. b 0 =0, to reduce the polynomial b(t); 
     Rule #3: When both least significant bits a 0 =1 and b 0 =1, and a(t)&lt;b(t), Operation 3 is applied. 
      When both least significant bits a 0 =l and b 0 =1, and a(t)&gt;b(t), Operation 4 is applied. 
     Rule #4: If a(t)=b(t), the division process is completed. 
     Operation 3 or 4 are used to zero the least significant bit of A or B such that Operation 1 or 2 can be repeated. To ensure a monolithic reduction of a(t) and b(t), only a smaller polynomial can be added to a larger one. 
     A right-shift operation on a bit-string in the register is equivalent to dividing the polynomial by t. For instance, a bit-string (11000100) represents a polynomial function ƒ(t)=t 7 +t 6 +t 2 . A right-shift operation produces a bit-string (01100010) which corresponds to the polynomial function ƒ(t)=(t 7 +t 6 +t 2 )/t=t 6 +t 5 +t. The operations 3 and 4 also obey the two invariant relationships. If A, U, B and V satisfy the relationships prior to the operation: 
     
       
           a ( t )* y ( t )= u ( t )* x ( t ) mod prime( t ) 
       
     
     
       
           b ( t )* y ( t )= v ( t )* x ( t ) mod prime( t ) 
       
     
     the equation b′(t)*y(t)=v′(t)*x(t) mod prime(t) will still be true after adding register A to B and register U to V, because 
      ( b ′( t )= b ( t )+ a ( t ))* y ( t )= v ′( t )= v ( t )+ u ( t ))* x ( t ) mod prime( t ) 
     
       
           a ′( t )* y ( t )= u ′( t )* x ( t ) mod prime( t ) 
       
     
     This process repeats itself until both A and B are one. At the end of the iteration process, the division is completed and the resulting polynomial is in the U register: 
     
       
           u ( t )= y ( t )/ x ( t ) mod prime( t ) 
       
     
     Since a(t)=b(t)=1 and a(t)*y(t)=u(t)*x(t) mod prime(t), we know that the bit-string in register U represents the result of the polynomial division. Thus, the polynomial division has been accomplished without two separate operations, an inversion followed by a multiplication. 
     This present invention can be implemented as an iterative process. The following example uses C-syntax pseudo-code, although the present invention can be implemented in any programming language. The pseudo-code below uses the four invariant operations defined previously, as follows: 
     
       
         
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
           
               
                   
                   
               
             
             
               
                   
                 Initialize registers A-U-B-and-V; 
               
               
                   
                 while (a0==0) Right-shift-registers-A-and-U; 
               
               
                   
                 while ( a(t) !=b(t) ){ 
               
             
          
           
               
                   
                 if ( a(t)&lt;b(t) ) { 
               
             
          
           
               
                   
                 Add-register-A-to-B-and-U-to-V ; 
               
               
                   
                 while (b0 ==0 ) Right-shift-register-B-and-V ; 
               
             
          
           
               
                   
                 } else if ( a(t) &gt; b(t) ) { 
               
             
          
           
               
                   
                 Add-register-B-to-A-and-V-to-U ; 
               
               
                   
                 while ( a0 ==0 ) Right-shift-register-A-and-V; 
               
             
          
           
               
                   
                 } 
               
             
          
           
               
                   
                 } 
               
               
                   
                   
               
             
          
         
       
     
     This process is illustrated in FIG.  1 . At step  101  registers A, B, U, and V are initialized with values a(t)=x(t), u(t)=y(t), b(t)=prime(t), and v(t)=0 such that the invariant relationships described above are satisfied. At step  102  the least significant bit of the value in register A is examined to determine if it is zero. If so, then a rightshift operation according to invariant operation 1 is performed on the register value at step  103 . The system then returns to step  102 . 
     If not, then the system proceeds to step  104  to determine if the LSB of register B is equal to zero. If yes, then a rightshift operation according to invariant operation 2 is performed at step  105  and the system returns to step  104 . If not, the system proceeds to step  106 . 
     At step  106  it is determined if the values of registers A and B are equal. If so, the operation ends. If not, it is determined at step  107  if the value of register A is less than B, then operation 3 is applied at step  108  and the system returns to step  104 . If not, step  109  determines if the value of register A is greater than the value of register B. If not, the operation ends. If so, the system performs operation 4 at step  110  and returns to step  102 . 
     An example of the efficiency gain is demonstrated by applying the invention to a scalar multiplication example. For example, assume Q=kP. Assume the scalar k is a 160-bit large integer: 
     
       
           k =(100 . . . . . . 01110 . . . . . . 01010 . . . . . . 001101)=((1*2 49 +7)*2 66 +5)*2 44 +13 
       
     
     The invention first breaks up the binary bit-string of the scalar k into two kinds of windows, nonzero-windows and the zero-windows: 
     
       
           k =(1 00 . . . . . . 0 111 0 . . . . . . 0 101 0 . . . . . . 00 1101) 
       
     
     The scalar multiplication can be decomposed into multiple iterations of repeated point-doublings and point-additions:                   Q   =     kP   =         (         (         2   49     *   P     +     7                 P       )     *     2   66       +     5      P       )     *     2   44       +     13      P                       =         2   44                     Q   1       +     13      P         ,   where                 Q   1     =           2   66                     Q   2       +     5      P                 and                   Q   2         =         2   49        P     +     7      P                                        
     The size of a zero-window can be as large as it needs to be. The size of a nonzero-window is limited by the size of the look-up table used in the system. The points, 7P, 5P, and 13P can be fetched directly from a look-up table. A table look-up is an effective technique for eliminating point-additions. Using a small 4-bit look-up table, one can potentially eliminate up to 75% of the point-additions in the system. Now the computation burden shifts over to the side of point-doublings. As can be seen from the table below, 159 point doublings result from 2 49  P, 2 44  Q 1 , and 2 66  Q 2  and consume significant computational resources. 
     Thus, the scalar multiplication above requires 159 point-doublings and 3 point-additions. Using prior art techniques, this would require as many as 324 multiplies. Using the present invention, the total number of multiplies in this scalar multiplication is reduced to 6. 
     
       
         
               
               
               
             
               
               
               
             
           
               
                   
                   
               
               
                   
                 Conventional approach 
                 New approach 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                 159 point-doublings 
                 318 multiplies + 159 inverts 
                 3 multiplies + 159 inverts 
               
               
                  3 point-additions 
                  6 multiplies + 3 inverts 
                 3 multiplies + 3 inverts 
               
               
                 Total 
                 324 multiplies + 162 inverts 
                 6 multiplies + 162 inverts 
               
               
                   
               
             
          
         
       
     
     Hardware Execution Environment 
     The present invention can be implemented as an elliptic curve crypto-accelerator in hardware. One possible embodiment is illustrated in FIG.  2 . Block  200  contains the five registers A, B, U, V, and M. Compare logic  201  is coupled to the registers and is used to compare the LSB&#39;s of registers A and B, to compare the values of registers A and B, and to execute the algorithm described in FIG.  1 . Invariant operations logic  202  is coupled to the registers  200  and to the compare logic  201  to implement the four invariant operations as appropriate. 
     Software Execution Environment 
     An embodiment of the invention can be implemented as computer software in the form of computer readable code executed in a general purpose computing environment such as environment  300  illustrated in FIG. 3, or in the form of bytecode class files running in such an environment. A keyboard  310  and mouse  311  are coupled to a bi-directional system bus  318 . The keyboard and mouse are for introducing user input to a computer  301  and communicating that user input to processor  313 . 
     Computer  301  may also include a communication interface  320  coupled to bus  318 . Communication interface  320  provides a two-way data communication coupling via a network link  321  to a local network  322 . For example, if communication interface  320  is an integrated services digital network (ISDN) card or a modem, communication interface  320  provides a data communication connection to the corresponding type of telephone line, which comprises part of network link  321 . If communication interface  320  is a local area network (LAN) card, communication interface  320  provides a data communication connection via network link  321  to a compatible LAN. Wireless links are also possible. In any such implementation, communication interface  320  sends and receives electrical, electromagnetic or optical signals which carry digital data streams representing various types of information. 
     Network link  321  typically provides data communication through one or more networks to other data devices. For example, network link  321  may provide a connection through local network  322  to local server computer  323  or to data equipment operated by ISP  324 . ISP  324  in turn provides data communication services through the world wide packet data communication network now commonly referred to as the “Internet”  325 . Local network  322  and Internet  325  both use electrical, electromagnetic or optical signals which carry digital data streams. The signals through the various networks and the signals on network link  321  and through communication interface  320 , which carry the digital data to and from computer  300 , are exemplary forms of carrier waves transporting the information. 
     Processor  313  may reside wholly on client computer  301  or wholly on server  326  or processor  313  may have its computational power distributed between computer  301  and server  326 . In the case where processor  313  resides wholly on server  326 , the results of the computations performed by processor  313  are transmitted to computer  301  via Internet  325 , Internet Service Provider (ISP)  324 , local network  322  and communication interface  320 . In this way, computer  301  is able to display the results of the computation to a user in the form of output. Other suitable input devices may be used in addition to, or in place of, the mouse  311  and keyboard  310 . I/O (input/output) unit  319  coupled to bi-directional system bus  318  represents such I/O elements as a printer, A/V (audio/video) I/O, etc. 
     Computer  301  includes a video memory  314 , main memory  315  and mass storage  312 , all coupled to bi-directional system bus  318  along with keyboard  310 , mouse  311  and processor  313 . 
     As with processor  313 , in various computing environments, main memory  315  and mass storage  312 , can reside wholly on server  326  or computer  301 , or they may be distributed between the two. Examples of systems where processor  313 , main memory  315 , and mass storage  312  are distributed between computer  301  and server  326  include the thin-client computing architecture developed by Sun Microsystems, Inc., the palm pilot computing device, Internet ready cellular phones, and other Internet computing devices. 
     The mass storage  312  may include both fixed and removable media, such as magnetic, optical or magnetic optical storage systems or any other available mass storage technology. Bus  318  may contain, for example, thirty-two address lines for addressing video memory  314  or main memory  315 . The system bus  318  also includes, for example, a 32-bit data bus for transferring data between and among the components, such as processor  313 , main memory  315 , video memory  314  and mass storage  312 . Alternatively, multiplex data/address lines may be used instead of separate data and address lines. 
     In one embodiment of the invention, the processor  313  is a microprocessor manufactured by Motorola, such as the 680X0 processor or a microprocessor manufactured by Intel, such as the 80X86, or Pentium processor, or a SPARC microprocessor from Sun Microsystems, Inc. However, any other suitable microprocessor or microcomputer may be utilized. Main memory  315  is comprised of dynamic random access memory (DRAM). Video memory  314  is a dual-ported video random access memory. One port of the video memory  314  is coupled to video amplifier  316 . The video amplifier  316  is used to drive the cathode ray tube (CRT) raster monitor  317 . Video amplifier  316  is well known in the art and may be implemented by any suitable apparatus. This circuitry converts pixel data stored in video memory  314  to a raster signal suitable for use by monitor  317 . Monitor  317  is a type of monitor suitable for displaying graphic images. 
     Computer  301  can send messages and receive data, including program code, through the network(s), network link  321 , and communication interface  320 . In the Internet example, remote server computer  326  might transmit a requested code for an application program through Internet  325 , ISP  324 , local network  322  and communication interface  320 . The received code may be executed by processor  313  as it is received, and/or stored in mass storage  312 , or other non-volatile storage for later execution. In this manner, computer  300  may obtain application code in the form of a carrier wave. Alternatively, remote server computer  326  may execute applications using processor  313 , and utilize mass storage  312 , and/or video memory  315 . The results of the execution at server  326  are then transmitted through Internet  325 , ISP  324 , local network  322  and communication interface  320 . In this example, computer  301  performs only input and output functions. 
     Application code may be embodied in any form of computer program product. A computer program product comprises a medium configured to store or transport computer readable code, or in which computer readable code may be embedded. Some examples of computer program products are CD-ROM disks, ROM cards, floppy disks, magnetic tapes, computer hard drives, servers on a network, and carrier waves. 
     The computer systems described above are for purposes of example only. An embodiment of the invention may be implemented in any type of computer system or programming or processing environment. 
     Thus, a method for efficient polynomial divide has been described.