[lazard]

Sorry about that. I need some way to prevent someone from quickly registering many email addresses. Do you have any other ideas?

[kragen]

What Gmail did when they started up was to give each early user a small number of invites to hand out to others. That way someone could quickly register, say, five email addresses, but only at the cost of being able to invite five of their friends.

[RobLach]

I don't beyond browser fingerprint+ip throttling which may be a step in the wrong direction. Does spark the idea to create a LibreCaptcha.

[tgragnato]

Registering a large number of rogue identities to exhaust the bandwidth seems to be one of the most practical attacks.

How do you consider that in the threat model of the research paper?