The Research of Large Numbers Adder to Rapid Realization Method

This paper has presented a method of carry forecast between groups to improve the speed of the large numbers adder in some cryptography and other applications. Firstly, the large numbers is divided into many groups, in which the delay of carry-chain is reduced by Carry look-ahead; second, the group addition operation is finished by carry forecast between groups; lastly, the addition sum of different carry forecast state was selected as the final result basing on the carry state. The delay of the large numbers addition which data width is more than 1024-bit is constantly 19 gate levels. Because of the carry transferring is translated into the carry state equation comparison, the carry delay of adder is not changing with the increasing of data width.