This paper presents a novel technique to build an access key that finds its natural fit in blockchain, smart cities environments, transactions of electronic currencies and, as proved by NIST tests, in high computer security scenarios where having a high level of secrecy is mandatory; furthermore, the key building procedure employs a biometric component to guarantee, with a reasonable level of certainty, the user identity. These characteristics are obtained by using an asymmetric cryptography algorithm (RSA) and Iris biometrics; both of them, taken singularly, exhibit some limits that can be overcome by joining the two approaches through Information Fusion (IF) techniques. In the follows, it will be presented the developed algorithm named Iris Information Fusion (IIF) that fuses a biometric component represented by the iris with a numerical component, in this case the product of two prime numbers which is the module of RSA algorithm.