HYBIRD CRYPTOSYSTEM ALGORITMA HILL CIPHER DAN ALGORITMA ELGAMAL PADA KEAMANAN CITRA
The development of technology at this time allows everyone to exchange information without any limitation of time and distance. The possibility that data leakage will occur during the process of exchanging information is carried out, therefore in sending data especially images, security aspects, confidentiality and efficiency of data storage is very necessary. If the important information falls into the wrong hands, it will cause unwanted things, for example manipulation of images with negative shapes and can harm the owner of the image. One method used to maintain data security is cryptography using one of the techniques, Elgamal. The strength of this algorithm lies in the difficulty of calculating discrete algorithms on prime integers in which multiplication operations are performed. In this research, the writer combines Hill Cipher to do image encryption and Elgamal Algorithm to decrypt the key of Hill Cipher. The image is first encrypted using the Hill Cipher, then the Hill Cipher key is encrypted using the Elgamal Algorithm. The implementation of the system uses the programming language Visual Basic Net 2010. The results of the implementation with the initial encrypted image has 4282.85 milliseconds with random images, while the encrypted image will be re-described as having 20442.84 milliseconds with the image returned to the beginning.