11. The method of claim 4 , wherein the bank of fingerprints used for the comparison when compressing a block of data is restricted to fingerprints corresponding to one or more subparts that occur after the last subpart in the secondary dictionary that is used for updating an initial compression dictionary when compressing a previous block of data.
4. The method of claim 1 , wherein determining at least one subpart that correlates the block of data to compress comprises computing fingerprints of several subparts of the block of data to compress as hash values of said subparts and comparing the computed fingerprints with a bank of fingerprints corresponding to subparts of the secondary dictionary.