Encoding for Robust Immutable Storage (ERIS)

[pukkamustard]

Hello GNUNet,

I'd like to request feedback, questions and comments on an 
encoding of
content very much inspired by ECRS that I have been working on: 
Encoding
for Robust Immutable Storage (ERIS)

https://openengiadina.net/papers/eris.html

The motivation is to use the encoding in a social network like 
settings
where short messages and interactions are encoded using ERIS (as 
RDF
[1]).

There is one major difference to ECRS (and a couple smaller ones) 
that I
would like to highlight:


** Verification capability

ERIS adds a verification capability. Holders of the verification
capability can enumerate all blocks required to decode the content 
and
verify integrity of the blocks without being able to decode the 
content.

This enables peers to cache the entire content without being able 
to
read the content.

The verification capability is enabled by using two keys:

1. A read key to encode the blocks holding content.
2. A verification key (which is deterministically derived from the 
read
  key) to encode the intermediary nodes of the Merkle tree.

This makes the scheme slightly more complicated than ECRS and also
requires a two-pass encoding (when using convergent encryption).

Nevertheless I believe this is a very important feature that maybe
results in a better privacy/complexity/availability trade-off as 
alluded
to in a previous thread
(https://lists.gnu.org/archive/html/gnunet-developers/2020-05/msg00015.html).


** Block size

Block size is chosen to be 4kB. This an optimization towards small
content (short messages and social interactions).


** URN

Encoded content can be referred to by a URN making it usable from
existing Web (and RDF) settings. This could be added to ECRS.


** No namespacing / keyword search

There are currently no SBlock or KBlock like features. The idea is 
that
these features can be built on-top of the base encoding (including
SBlock and KBlock).



We have a little JavaScript demo: 
https://openengiadina.gitlab.io/js-eris/ . As well as 
implementation in Guile [2].

I'd be very happy for your insight and feedback.

Thanks!

-pukkamustard


[1] https://openengiadina.net/papers/content-addressable-rdf.html
[2] https://gitlab.com/openengiadina/data-model/