legally binding digital sigs

[Atom Smasher]

does anyone know what makes a digital signature legally binding (or not) 
under US law?

thanks...


-- 
         ...atom

  _________________________________________
  PGP key - http://atom.smasher.org/pgp.txt
  762A 3B98 A3C3 96C9 C6B7 582A B88D 52E4 D9F5 7808
  -------------------------------------------------

 	"These numbers have nothing to do with the technology of
 	 the devices; they are the maximum that thermodynamics will
 	 allow. and they strongly imply that brute-force attacks
 	 against 256-bit keys will be infeasible until computers
 	 are built from something other than matter and occupy
 	 something other than space."
 		-- Bruce Schneier, Applied Cryptography