A computer-implemented method is disclosed for generating a signature representing an input bit vector. A signature generator generates a primary min-hash value based on a primary permutation from a sequence of permutation blocks. If the primary min-hash value is lower than a threshold value, a secondary min-hash value is generated based on a secondary permutation from the same permutation block. The signature generator then determines one or more signature values based on the primary min-hash value, the secondary min-hash value or both. The one or more signature values are stored as elements of the signature.