[dredmorbius]

Incorrect on public keys. You do not need a trusted channel to receive a key. You could receive one via smoke signal, carrier pigeon, or billboard. Existing key distribution systems may or may not be encrypted, but the reason for encrypting the channel is far more to protect the interests of the requestor than the integrity of the key itself. That last is independent of the key distribution channel.

What matters is that the web of trust associated with that key is sound (that is, you have assurance that the key belongs to whom you think it does), and that the integrity of the private key has been maintained.

The first of those problems is difficult, but not intractable. The second problem is rather difficult, especially in the case of persistent data, though the core requirement is that the key was valid when a message was generated, if you're looking at the sender of information. For your own information, you are relying on the recipient to maintain integrity over their private (decryption) key going forward, such that the data you'd transmitted remains encrypted against all others.

The first problem you point out, that any encrypted channel is not necessarily a secure channel, is valid, though given your misunderstanding on subsequent points I'm not sure how well that applies to this discussion (I still need to RTFA).

[michael_storm]

> Existing key distribution systems may or may not be encrypted, but the reason for encrypting the channel is far more to protect the interests of the requestor than the integrity of the key itself.

btrask wasn't saying that encryption is necessary for key distribution; he/she was saying that HTTPS guarantees identity and integrity, both of which are necessary to trust a key.

> What matters is that the web of trust associated with that key is sound (that is, you have assurance that the key belongs to whom you think it does), and that the integrity of the private key has been maintained.

That's a possible alternative to btrask's proposal, though you're equating "assurance that the key belongs to whom you think it does" with "web of trust". btrask's proposal is a special case of that, in which the web of trust is simply the sender.

> The first problem you point out, that any encrypted channel is not necessarily a secure channel

Correct, but not what btrask said. The first problem he pointed out was the fact that clients need to know whether a host expects secure communication before ever connecting to it.

> though given your misunderstanding on subsequent points I'm not sure how well that applies to this discussion

That's not very nice.

[dredmorbius]

Clarifying my own post: I'm insisting that neither a trusted or an ecrypted channel are necessary.

I said that an encrypted channel could be used, and that it might not be, but that if used encryption would largely serve as a protection to the requestor, who might otherwise be subject to traffic and/or interest analysis based on the specific keys they requested, which could be presumed to be of interest, or signing keys (I'm thinking PGP protocol here) of keys of interest. Either piece of information would reduce search space for an Eve.

I'm not equating trust of keys to web of trust, I'm stating that in existing (PKI/PGP) protocols, that is the assurance mechanism. And it is independent of either trust OR encryption of the key delivery channel itself.

There seems to be a rather profound difficulty in distinguishing what I've said with what I've said btrask said. I'm not sure how I could be clearer, but I'm open to pointers.

[michael_storm]

You're both right. I only replied because you responded to points that btrask hadn't made, then claimed he/she misunderstood the topic.

[btrask]

I said trusted, not encrypted. I wasn't talking about private keys at all. I think I understand the issues involved. Thanks though.

[dredmorbius]

And I still disagree on that point.

Maybe I misunderstand (though I also think I understand teh issues involved pretty well), or maybe one or the other or both of us are communicating poorly.

How would you distinguish a trusted, encrypted, and untrusted channels, say?

[btrask]

In the context of sharing public keys, I'd say you merely need authentication. Web of Trust being one possible mechanism. This isn't a particularly advanced topic.

Relevant to my original post, information about whether the connection should be encrypted also merely needs to be authenticated, not encrypted itself. Of course, the HSTS preloading site uses HTTPS (with encryption) because it's easy and why not.

[dredmorbius]

Thanks. So re keysharing, authentication is a form of secure channel.

I'm reading the auth and channel as independent. Auth is something of a metachannel, perhaps.

[btrask]

Fair enough. :)

[nicky0]

What if someone intercepts the carrier pigeon and swaps in a different public key of their own?

[dredmorbius]

Then the signatures don't match, or the fingerprint is wrong. If you're relying on long-term data access, messages encrypted against or signed by the true key don't match. This is an area in which PGP and SSH differ markedly. PGP is used to encrypt and authenticate data which tends to persist, SSH data used only in session. While both can use long-lived keypairs, it's the PGP keys you're more likely to notice changing (though SSH cclients tend to report this happening).

Yes, that means verifying your keys, and probably through an out-of-band method.