The Court can presume about the legality of digital signature on the electronic record under Indian Evidence Act when it is: 

Any electronic signature if kept in a proper custody for 5 years it may be resumed by the Court to be genuine. The Court may call for proof on it.   S. 90A Presumption as to electronic records five years old. — Where any electronic record, purporting or proved to be five years old , is produced from any custody which the Court in the particular case considers proper, the Court may presume that the electronic signature which purports to be the electronic signature of any particular person was so affixed by him or any person authorised by him in this behalf. Explanation. —Electronic records are said to be in proper custody if they are in the place in which, and under the care of the person with whom, they naturally be; but no custody is improper if it is proved to have had a legitimate origin, or the circumstances of the particular case are such as to render such an origin probable.