[tahoe-dev] nice new picture of DSA-based encryption, plus key length ideas

[zooko]

Following-up to my own post:

On Jan 8, 2008, at 8:16 PM, zooko wrote:

> protection   symmetric  dl key  dl group  hash
> ----------   ---------  ------  --------  ----
> option A     100        200     2358      256
> option B     256        512     15,424    512
>
> Option A: maybe these caps will become distrusted within a decade or
> two.  Maybe they will last for many decades.
>
> Option B: these will remain highly trusted, even for high-value data,
> for many decades, even in the face of quantum computation and small
> cryptanalytic results against the crypto primitives unless there is a
> very surprising cryptanalytic result against the crypto primitives

Having mulled it over a bit, I'm inclined to go with Option A for  
now.  Tahoe will then have more convenient caps -- 200-bit write caps  
and 100-bit read caps (see examples below), and will still be strong  
cryptography which should be trusted by experts for many years unless  
there are surprising new results in computation (such as quantum  
computation) or cryptanalysis.

We can later add bigger, stronger, crypto if we gain users who are  
more conservative, whose data is of higher value, and who intend to  
store their data in tahoe grids for the long-term -- decades.

Regards,

Zooko

P.S.  Examples of high-security 512-bit write caps, and of more  
convenient and efficient 200-bit write caps and 100-bit read caps:

> 512-bit write caps:
>
> LiuZU0CCvv3HbKmRU2wqqR9GSDOg_6DAT6YHm2MYgmzrtPmHN_kv77zHlKhkUP3Q7YE5Fg 
> OWmeR0uNq6l_Lb2g
>
> 200-bit write-caps would look like this:
>
> biGvBl4XzCGJBqmV7lZllrubc3w5muyPRg
>
> 100-bit read-caps would look like this:
>
> McwduQ4rn7U4Yg90vA