Date: Mon, 26 Sep 2016 22:48:12 +0200 From: =?utf-8?Q?Dag-Erling_Sm=C3=B8rgrav?= <des@des.no> To: freebsd-security <freebsd-security@freebsd.org> Cc: RW <rwmaillists@googlemail.com> Subject: Re: Two Dumb Questions Message-ID: <86r3868k1f.fsf@desk.des.no> In-Reply-To: <20160926135238.6296ddc2@gumby.homeunix.com> (RW via freebsd-security's message of "Mon, 26 Sep 2016 13:52:38 %2B0100") References: <32084.1474872154@segfault.tristatelogic.com> <20160926135238.6296ddc2@gumby.homeunix.com>
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RW <rwmaillists@googlemail.com> writes: > There's a simple paint analogy here: > > https://en.wikipedia.org/wiki/Diffie=E2=80=93Hellman_key_exchange > > that illustrates how it's possible to exchange a shared secret without > an eavesdropper knowing what it is. The shared secret can then be used > for symmetric encryption using something like AES. SSL / TLS didn't commonly use DH, much less *safe* DH, until fairly recently, and DH alone is not very useful. You need either a shared secret or trusted key pairs to authenticate either or both endpoints. > Actual protocols use public key cryptography so it can be established > that the exchange is end to end, and not broken into two separate > exchanges. Assuming you can trust the public key, which is what CAs are for, but CAs can be hacked, deceived or coerced. DES --=20 Dag-Erling Sm=C3=B8rgrav - des@des.no
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