Implementation of Information and Communication Technology (ICT) to assist document management in the mail distribution will be useful in improving document management performance effectively and efficiently. Securing information in mail disposition using electronic media should be made in such an order to prevent unwanted things. Cryprography or digital signature are some of the techniques that ensures security. The purpose of this study is to see the effect of digital signatures to maintain data security using Rivest-Shamir-Adleman (RSA) and Advanced Encryption Standard (AES) algorithms to the disposition system of letter based on cryptographic purposes, namely Secrecy, Data Integrity, Authentication and Non-repudiation. Several tests of various attacks to the system were conducted. The study concluded the additions of AES algorithm can maintain secrecy and integrity of the letters, while RSA algorithm can maintain authentication and non-repudation of the letters.