random string generator

@echo off & setlocal EnableDelayedExpansion

set chars=abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789
set /A charset=26+26+10
set /A stringLength=16

set string=
for /L %%a in (1 1 %stringLength%) do (
    call:rand 1 %charset%
    set /A charIndex=!randomNum!-1
    call set extractedChar=%%chars:~!charIndex!,1%%
    set string=!string!!extractedChar!
)
echo %string%
pause

goto:EOF

:rand
set /A randomNum=%random%*(%2-%1+1)/32768+%1
goto:EOF