IT FOR SOCIETY, Vol. 04, No. 01 ISSN 2503-2224 16 Information Hiding Application Using Digital Images Secured With Rijndael and Caesar Cipher Encryption Jonathan Surya 1 Abdul Ghofir 2 President University Bekasi, Indonesia 1 jonathan@gmail.com 2 geoff@president.ac.id Abstrak - Steganography is a way thtt conceals or embeds important data in form of text file into an image which possible to reduce and erase the existence of the data. A modern steganography can help millions of people to protect their data from potential threats or other individuals using computer programs and algorithm. This paper proposed an implementation of steganography Rijndael and Caesar schemes . This application will let the user embed the important data/information to an image and encrypt it. 1. Introduction Steganography application is created to make the user’s data safe and easy to use it. The application will be implemented in windows 10 operating system. By using this application, the user could prevent the percentage of several threats and increase their security needs. Cyber attacks in Indonesia are increasing year to year. That case has been attracting government to do more protection in order to save important things as many as possible, even though the security is already complex but someone will be able to bypass it. Concerning those activities, it is better to hide the existence of the important data. in order to protect the data its better to eliminate the possible threat by hiding its existence. However this activities not only affected national level, it can find it in human daily life for example, when someone peeking other person phone while typing something in their phone or when someone able to bypass someone else password and peeking the phone text, media, etc. The application works on windows platform and will act as a system which enable the user to conceal important data. The application is expected to be able to conceal or embed data inside the image without changing the image color significantly, in order to divert the potential attacker. Then the user can choose to add more security by using password(rijndael) and Caesar Cipher encryption, this also application has a user-friendly design which enabled the user to easy to use the application. 2. Digital Images Digital images are made of picture elements called pixels. Typically, pixels are organized in an ordered rectangular array. The size of an image is determined by the dimensions of this pixel array. The image width is the number of columns, and the image height is the number of rows in the array. Thus the pixel array is a matrix of M columns x N rows. To refer to a specific pixel within the image matrix, we define its coordinate at x and y. The coordinate system of image matrices defines x as increasing from left to right and y as increasing from top to bottom Image file formats are standardized means of organizing and storing digital images. Digital image files are composed of digital data in one of these formats that can be rasterized for use on a computer display or printer. An image file format may store data in uncompressed, compressed, or vector formats. Once rasterized, an image becomes a grid of pixels, each of which has a number of bits to designate its color equal to the color depth of the device displaying it. There are 4 possible images format that can be used in this application, such as: GIF, PNG, TIFF, BMP. 3. Rijndael Encryption AES is based on a design principle known as a substitution– permutation network, and is efficient in both software and hardware. Unlike its predecessor DES, AES does not use a Feistel network. AES is a variant of Rijndael which has a fixed block size of 128 bits, and a key size of 128, 192, or 256 bits. By contrast, Rijndael per se is specified with block and key sizes that may be any multiple of 32 bits, with a minimum of 128 and a maximum of 256 bits. AES operates on a 4 × 4