The present invention relates to a method of generating a secure RSA key by a server comprising the steps of: •generating (S1) a private RSA key d and a RSA modulus integer N; •splitting (S2) the secret key integer d in j key shares dJ of length n, with j in [1, J], J being an integer, and such that d=d1+d2+ . . . +dJ mod phi(N), with each key share dj being equal to (dj(0) . . . dj(i) . . . dj(n/b−1)) with each key share component dj(i) in {0 . . . 2{circumflex over ( )}b−1} and i in [0, n/b−1], b being an integer inferior to n and phi the Euler's totient function; •encrypting (S3) with a fully homomorphic encryption (FHE) algorithm each key share component dj(i) of the private RSA key d by using a Fully Homomorphic Encryption secret key ps of a set Ss comprising the index couple (i,j), to generate an encrypted key share component edj(i) of said secure RSA key, said set Ss being a set of integer couples, among a predetermined integer number u of disjoint sets {S1, S2 Ss, Ss+1, . . . Su} generated such that: U{Ss}={(i,j) such that i in [0, n/b−1], j in [1, J]} and each said set among {S1, . . . Su} being associated with a Fully Homomorphic Encryption (FHE) secret key.