Abstract :
Cryptography is one of science that learn about securing a message. Message
security is done by randomizing the message (encryption) and returned to it?s original
form (description). In this study, the designer of the system first and build an
application to secure the message by using the Fold Algorithm method that aims to
secure messages consisting of letters, numbers, or symbols. Applications are designed
and built running on Mobile Android. The Fold Algorithm Method applies a fourfold
system in the encryption process and the description of the message to be encrypted
and in the description will advance 4 (four) characters forward or backward. Based
on testing done the application managed to perform the encryption process and
description correctly, ranging from short messages to messages as much as 2305
characters.