CONFIDENTIALITY OF INFORMATION AND SECURITY OF THE SYSTEMS is the must topic you have to write in SRS. You can write following things in Security of the System topic:

Each party acknowledges that all material and information which has or will come into the possession and knowledge of each in connection with this Agreement or the performance hereof, consists of confidential and proprietary data, whose disclosure to or use by third parties will be damaging, Both parties, therefore, agree to hold such material and information in strictest confidence, not to make use thereof other than for the performance of this Agreement, to release it only to employees requiring such information, and not to release or disclose it to any other party.