Re: Help with hashing and signatures

[Alessio Vanni]

(The conversation has gone off-list for the last couple of messages.
Since this it has been resolved I'm sending this to the list too to let
it known that it's done.)

"Schanzenbach, Martin" <mschanzenbach@posteo.de> writes:

>> The misleading factor is that it's unclear when the ego (in this case
>> the argument `e') is not valid anymore.
>> 
>
> Ah good catch. I rarely use ego_lookup. I usually connect to the identity
> service and use the callback. See below why.
>
>
>> Does the ego become invalid when the `ego_callback' function terminates?
>> If so, how can I make a copy of the private key? Is `memcpy' enough or
>> do I have to consider some other conditions?
>> 
>
> Yes, you can memcpy it. Or just assign it:
>
> mystruct.privkey = *eqk;
>
>> Another question is why does the private key have this property? Can't
>> the function return a new allocated structure or fill one passed as
>> argument, instead?
>> 
>
> The ego struct's lifetime is limited to the callback for lookup
> functionality of identity. See identity_api_lookup.c::125
>
> If you use "h = GNUNET_IDENTITY_connect (cfg, ego_cb);"
> you will receive all current egos. You can store them in a list.
> Those egos lifetime will be the same as the handle "h". So you
> can use the keys until you disconnect (GNUNET_IDENTITY_disconnect(h)).
>
> If your program may use more than one ego, then the above is probably
> better. See how, for example, identity/plugin_rest_identity.c is using it.
>
> BR

I tried using `GNUNET_memcpy' to get a copy of the private key and in
fact now it works, showing that the problem was indeed connected to the
lifespan of the ego provided by `GNUNET_IDENTITY_ego_lookup'.

Even though a part of the application does allow changing egos, in terms
of changing code and testing, looking up a single ego and making a copy
of the key takes less work and is already tested, so unless there happen
to be special considerations to take I'm going to roll with it; I'll
keep in mind the other method for when I need a better control over the
lifespan of the egos returned by the identity service.

Thank you for your time.
A.V.