Title: DATA PROCESSING

Data Processing

In GNUnet, files and data are transmitted in blocks B, where each block is of size 1024 Bytes. The content of each block is symmetrically encrypted, where the encryption key is the result of an application of the hash function h to the content of the block B, denoted as h(B). In GNUnet, RIPEMD-160 [1] is used as hash function h. Thus the encrypted block Eenc , which is to be transmitted in GNUnet, is right Eenc = Eh(B)(B). Encrypted blocks are stored in a hash map with lookup key h(h(B)). Lookup requests are of the form h(h(h(B))).

Files or data that are larger than 1024 Bytes are to be distributed to several blocks. In addition, an index block I = h(B1), … , h(B52), CRC32(B1, … , B52) is created. This index block is then stored the same way as the content blocks, that is encrypted with key h(I) in the same hash map with lookup key h(h(I)). In the case the data to be transmitted in GNUnet is greater than 52 Blocks, more index blocks will be created as needed. This yields a tree structure of index blocks. The root index is of particular importance, since it is encrypted with right that hash value of the lookup key, which is published in GNUnet for the entire block.