Publication

To introduce a file F into the servnet, the publishing server first uses Rabin's information dispersal algorithm (IDA) [35] to break the file into shares $f_1, \dots, f_n$ where any k shares are sufficient to recreate the file. The server then generates a key pair (PK_doc,SK_doc), constructs and signs a data segment for each share f_i, and inserts those segments as new documents into its local server space. Attributes in each share include a timestamp, expiration information, the public key which was used to sign it (for integrity verification), information about share numbering, and the signature itself.

The robustness parameter k should be chosen based on some compromise between the importance of the file and the size and available space. A large value of k relative to n makes the file more brittle, because it will be unrecoverable after a few shares are lost. On the other hand, a smaller value of k implies a larger share size, since more data is stored in each share.