A method for processing blocks of data in a file is provided. The method includes determining a plurality of blocks of data in the file for a compression process used for compressing data in the file. This process is iterated over all the plurality of blocks of data in the file. A block of data is read into memory, and the offset from which it is read is also stored. A strong collision-resistant cryptographic hash representation, such as a strong collision-resistant cryptographic hash, of the block is determined. The cryptographic hash representation (CHR) of the block of data as well as the data itself, is added to a table with the CHR as a unique index. The offset of the block of data in the source file, as well as the CHR for that block are appended to a separate table.