cation rate. This extends a result of Willems et al. [8] showing that the maximum identification rate of a biometrical system is equal to the mutual information between the enrollment and identification observations, see also [4]. A crucial observation to obtain this result is that a set of biometric enrollment vectors can be regarded as a random channel code.In the current manuscript we focus on speeding up the search process, as in [9]. We are not interested in compressing the database as in [5], [6]. We will show that in an informationtheoretical setting quantization methods are optimal.To demonstrate what we mean by quantization, suppose that the system upon observing an individual, first detects to which cluster the individual belongs, and after that decides about the individual itself (two-stage identification). If there are M individuals, an ideal systems will have v'iJ clusters each containing v'iJ individuals. To determine the cluster index v'iJ candidate-clusters can be checked, and then to determine the individual within the cluster, v'iJ refinement-checks are needed. This results in 2v'iJ checks in total, considerably less than the M checks that are required for exhaustive search. In general however individuals can be in more than one cluster, see Fig. 1, and then the number of cluster-checks times the number of refinement-checks exceeds the number of individuals. Here we investigate the fundamental trade-off between cluster-check rate and refinement-check rate.An important point is what we mean by a cluster-check. In principle a cluster-check could correspond to v'iJ subchecks, one for each individual within the cluster. To prevent this, we require the device that makes the cluster-decision to be "ignorant" of the biometric enrollment vectors. Under this assumption an optimal system contains an ignorant device that acts as a vector quantizer.In the next section we present our model of a biometrical identification system based on two-stage identification and we