>>deatha+J06
There isn't one. As far as I know, no one really knows for sure how they bypass all these paywalls. (Most credible theory I heard: They actually just pay for the subscriptions.)
>>mr_mit+Zk6
Most paywalls just allow search engines to read their content just fine. Because they do want discoverability, they want their cake and eat it.
There's a few publications that don't even do that though and archive.is is very good at bypassing them so I do imagine they use logins for those, but for the masses of sites it's not currently necessary.