Kayden successfully cracked the final round of interview at an organization. After few days, he received his offer letter through an official company email address. The email stated that the selected candidate should respond within a specified time. Kayden accepted the opportunity and provided e-signature on the offer letter, then replied to the same email address. The company validated the e-signature and added his details to their database. Here, Kayden could not deny company's message, and company could not deny Kayden's signature.
Which of the following information security elements was described in the above scenario?