An online business has a reliable log of all customer transactions. The log does not provide non$-$repudiation although all customer transactions are logged, the customer may argue that logs can be altered or made up by the business. In this scenario what can be done to ensure non$-$repudiation?

Question $23$ options:

Have all customer transactions logged also by an independent trusted third party.

Use encryption to log all transactions. This way alterations can be easily detected.

Duplicate logs that way, if one is lost there is another log to depend on

Delete all the logs so no one can dispute a transaction