Análise e comparação de algoritmos para criptografia de imagens

Abstract

Since the beginning of the exchange of information and the race to power, it was necessary to send messages between people, who are connected by a purpose, without unauthorized people knowing the content of that information. Thus, it was created a way to protect data from unauthorized access, called encryption (in his translation: Kripto - "hidden, secret, obscure, unintelligible" and grapho - "writing"). This is nothing more than a way to hide the data so that only authorized persons can gain access to it. In computer systems the information exchange occurs on a very large proportion and are several messages sent per second by means of communication (corporate network and/or Internet). In the encryption process the information is shuffled with a matching key, which can be private or public. To scramble the information in computer systems, one should use some of the available algorithms, which can be symmetrical or asymmetrical. In symmetric ones the encryption and decryption only happen with the private key, while the asymmetric use the public key to encrypt data and the private key to decrypt it. In a symmetrical communication a key is created for eachmessage sent, and this key must be shared with who needs this information through the unreliable channel. In the asymmetric communication, each communication point has a key pair and only the public key of each one is shared. Symmetric algorithms are characterized by fast processing and asymmetric ones for slowness. The scope of this work refers to the sharing of traffic images, captured by fixed speed cameras, in which the image is sent through an insecure channel out of the processor installed in place until the fine’s processing point. To avoid that the image would be intercepted and used in bad faith by unauthorized persons is necessary to make it unintelligible while travelling over the network, but returning again to a clear picture at the end of the process. This work demonstrates the performance time according to the key size in cryptography images using the symmetric algorithms AES, Blowfish, RC2, RC5, RC4, DES and 3DES and asymmetric RSA, and also demonstrates the performance in the image integrity during the process. It were used size keys of 128, 192 and256 bits for the AES algorithms Blowfish, RC2, RC5 and RC4, while for DES and 3DES it were used fixed key sizes as described in the specification of each one (64 and 192 bits respectively), for the RSA algorithm were used size keys of 2048, 4096 and 16384 bits. Therefore, this paper concludes that the best method to encrypt large amounts of bits (images) is the use of RSA together and RC5 algorithms.