There are two features in the slides that need to be accounted for in any explanation.
1. The second slide, which implies that the fact that the internet traffic passes through the US is relevant.
This implies that either some physical interception was necessary, either from outside the companies, or from the inside with their cooperation, or that it was legally necessary (on order to require the companies to deliver the information. And yet it would seem like the issue of what the NSA could require US companies to reveal, is orthogonal from which traffic passes through the US, since in that case the issue would be what was stored on US servers.
2. The implied cooperation from the companies in the slides. According to the Washington Post, the "Special Source Operations" in the logo refers to "the NSA term for alliances with trusted U.S. companies". Given this, and the use of the terms "providers", it seems unlikely that no cooperation from the companies is involved.
From the above, I would propose that the PRISM scheme must involve some combination of physical interception, and cooperation from the companies involved.
For example, the NSA may be intercepting traffic then asking the companies for private keys for some of the traffic they intercept. This would fit the above facts in that it requires the traffic to pass through the US, and also requires cooperation from the companies.
1. The second slide, which implies that the fact that the internet traffic passes through the US is relevant.
This implies that either some physical interception was necessary, either from outside the companies, or from the inside with their cooperation, or that it was legally necessary (on order to require the companies to deliver the information. And yet it would seem like the issue of what the NSA could require US companies to reveal, is orthogonal from which traffic passes through the US, since in that case the issue would be what was stored on US servers.
2. The implied cooperation from the companies in the slides. According to the Washington Post, the "Special Source Operations" in the logo refers to "the NSA term for alliances with trusted U.S. companies". Given this, and the use of the terms "providers", it seems unlikely that no cooperation from the companies is involved.
From the above, I would propose that the PRISM scheme must involve some combination of physical interception, and cooperation from the companies involved.
For example, the NSA may be intercepting traffic then asking the companies for private keys for some of the traffic they intercept. This would fit the above facts in that it requires the traffic to pass through the US, and also requires cooperation from the companies.