mod_add_64.m

%
% modular addition for 2^64
%
function out = mod_add_64(a_hex, b_hex)
    a = a_hex;
    b = b_hex;
    %
    % split a, and b into left, and right parts in char string type
    a_left = a(1:8);
    a_right = a(9:16);
    b_left = b(1:8);
    b_right = b(9:16);
    %
    % convert a, and b into decimal type
    a_left_dec = hex2dec(a_left);
    a_right_dec = hex2dec(a_right);
    b_left_dec = hex2dec(b_left);
    b_right_dec = hex2dec(b_right);
    %
    %     
    a_b_right_dec = uint32(mod(a_right_dec + b_right_dec, 2^32));
    a_b_right_qu = floor((a_right_dec + b_right_dec) / (2^32));
    a_b_left_dec = uint32(mod(a_left_dec + b_left_dec + a_b_right_qu, 2^32));
    %
    a_b_left_hex = dec2hex(a_b_left_dec, 8);
    a_b_right_hex = dec2hex(a_b_right_dec, 8);
    %
    % concatenate left and right string
    a_b_hex = strcat(a_b_left_hex, a_b_right_hex);
    out = a_b_hex;
return