Re: [GNUnet-developers] ripe-md160/HashCode160/CRC/MD5

[Christian Grothoff]

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

On Sunday 07 December 2003 11:17 am, jan marco alkema wrote:
> Hello Christian,
>
> I have downloaded 2 different Ripemd160 source code distributions and 1 crc
> source code program.
>
> I can't match the ripe-md160/crc with the gnunet "GNUNET_URI" for
> marije_004.jpg
>
> Christian, Maybe I do something wrong?

No, the GNUnet URL for a file has nothing (!) to do with the direct 
ripe/crc32/md5 hash of that file.  Read 
http://www.ovmj.org/GNUnet/download/ecrs.ps for the details of the GNUnet 
encoding.  The summary is, that taking the hash of the entire file means that 
you can only verify the integrity of the entire file, not of individual parts 
of the file.  Since we want to be able to securely retrieve parts of the file 
from different, possibly malicious peers, we need to be able to verify the 
file-integrity on a more fine-grained level, which is what ECRS (previously 
called ESED2) allows us to do.

Christian

> Greetings Jan Marco
>
> Appendix Hashes:
>
> RipeMD160(marije_004.jpg): bfd5d02dd853ad075e5413f0616bf1ee0c0af113
>
> MD5(marije_004.jpg): E5D0CC3887595816D48D983D0DC341AD
>
> CRC(marije_004.jpg): 68ce0184
>
> FileSize(marije_004.jpg): 33736
>
> # ./gnunet-insert --key=mary4 /home/janmarco/marije_004.jpg
> Inserting marije_004.jpg (no description supplied, unknown) under keyword
> mary4.
> # ./gnunet-search mary4
> gnunet-download -o "marije_004.jpg" --
> gnunet://afs/3CC486373A389B854F26710EAD6F9D70327CF93E.37EDB64A937600C185485
>8 A8A9131B53BC64EEFA.60713D60.33736
>
>
>
> _______________________________________________
> GNUnet-developers mailing list
> address@hidden
> http://mail.gnu.org/mailman/listinfo/gnunet-developers
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.0.7 (GNU/Linux)

iD8DBQE/06J49tNtMeXQLkIRAh8AAJ47YCkiSm67mRvoWuen2h14Buqj1gCdFhip
Ny7kbkYlS51fFoKQL0iyysw=
=P8IQ
-----END PGP SIGNATURE-----