There are a few things you could use to make your script better. WinActivate, clipboard, and improved mouse movement seem to be good ones to add. 

^+!a::
    clipboard =                  ; clears clipboard
    Click Right                  ; execute in browser
    MouseMove, 18, 15, 50, R     ; Moves mouse relative to start location
    Click Left     
    ClipWait, 2                  ; Waits 2 seconds for clipboard to contain something
    WinActivate, Slickedit       ; Switch to text editor
    WinWaitActive, Slickedit
    Send % clipboard             ; paste in text editor
    WinActivate, ahk_class Chrome_WidgetWin_1 ; or your browser of choice
Return


Use the included Window Spy to find the correct Window titles or classes to be used in the WinActivate commands.

Autohotkey: task to copy from browser and paste on text editor
I've been looking for a simple which signs a number with some randomly generated key and then verified(decrypts the original number) with the public key, which is generated by the private.

All the examples I've found does not feature an example with real numbers, and all the keys/numbers described with a single letter, which is not really that clear.
