This research aims to know the meaning from the semiotic signs on the movie poster. The data is collected from movie poster “the shutter island” which is taken from internet site. This study used qualitative approach since the researcher focused on identifying the sign found in the movie poster of The Shutter Island. This study applied some theories of semiotics, there are theory of sign by Saussure (1974) and some other theories such as Theory of  Colour  Term by Wierzbicka (1996) which is used for identifying the meaning of colors found in the movie poster and Verbal and Visual Aspect Theory by Dyer (1986) which applied for identifying verbal sign and visual poster in this research. It can be concluded that there are two aspects which is formulated in movie poster Shutter Island, they are verbal and visual aspect. The verbal aspect includes some categories such as the masthead which exolained who is the main character in this movie, the title of the film to inform the audience about the film, where the line on the poster inform the audience the spoiled that it was the island where once people got into that island, it could be so difficult for the to get away from the island, and it shows the date the film will be released.

As a public key cryptography algorithm, the Rabin algorithm has two keys, i.e., public key (n) and private key (p, q). The security of Rabin algorithm relies on the difficulty of factoring very large numbers, so the greater the private keys are used, the better the security becomes. In order to test how hard it is to cryptanalyze the Rabin public key n, we use the Fermat factorization method to obtain the values of p and q. After obtaining the factors, both of these factors are tested whether or not they are in accordance with the Rabin private key requirements. The first is to test whether or not the factors are prime numbers using Fermat Little Theorem. The second is to test whether or not the factors are congruent to 3 in modulo 4. If the results of the two tests turn out to be positive, then the factors are indeed p and q, the private keys of the Rabin algorithm. The result of our experiment indicates that the value of public key n does not have a directly proportional correlation to the factoring time. A factor which may affect the factoring time is the difference between the private keys (p - q): the larger the difference, the longer the factoring time.