A robust fingerprinting system is disclosed. Such a system can recognize unknown multimedia content (U(t)) by extracting a fingerprint (a series of hash words) from said content, and searching a resembling fingerprint in a database in which fingerprints of a plurality of known contents (K(t)) are stored. In order to more efficiently store the fingerprints in the database and to speed up the search, the hash words (H(n)) of known signals (K(t)) are sub-sampled (13) by a factor M prior to storage in the database (14). The hash words (H(n)) of unknown signals (U(t)) are divided (16) into M interleaved sub-series (H0(n) . . . HM-1(n)). The interleaved sub-series are selectively (17) applied to the database (14) under the control of a computer (15). If only one of the sub-series sufficiently matches a stored fingerprint, the signal is identified.