Authentication from cookie data in mobile app

need to get a user authenticated in a mobile app from credential existing in the cookie sent .

an object which contains all ingredients from MobileApp cookie to authenticate mobile user:

 public class MitCredentials
    {
        /// <summary>
        /// Gets or sets a BreadcrumbId which is stored in a MobileApp credentials cookie. 
        /// </summary>
        [DataMember]
        public string BreadcrumbId { get; set; }

        /// <summary>
        /// Gets or sets a CREDENTIAL_TYPE which is stored in a MobileApp credentials cookie. 
        /// </summary>
        [DataMember]
        public string CredentialType { get; set; }

        /// <summary>
        /// Gets or sets a INTERESTED_PARTY_PUBLIC_ID which is stored in a MobileApp credentials cookie. 
        /// </summary>
        [DataMember]
        public string InterestedPartyPublicId { get; set; }

..... I need to send this via service to authenticate a user in a mobile app

How can I proceed? Do I need to create an interface and another class to implement this interface.

What are the steps please