3 ms·

Note that the primary HTML resource for most web pages takes multiple roundtrips to transmit completely. If you sign it only at the end, you've made the browser

Note that the primary HTML resource for most web pages takes multiple roundtrips to transmit completely. If you sign it only at the end, you've made the browser feel slower. So you'd have to avoid the RTT by accepting, processing, and presenting the data immediately but only later authenticating it retroactively. The bad guy can just drop or delay the legitimate signature. This is inherently error-prone. It gives the developers a big, convenient, and reassuring assumption which the attacker is able to violate. For a complex and evolving endpoint like a web browser, I don't think you'd ever see the end of security bugs. More: https://www.ietf.org/mail-archive/web/tls/current/msg04017.html https://www.ietf.org/mail-archive/web/tls/current/msg04017.h... Furthermore, retroactive authentication still doesn't preclude the encryption: https://www.ietf.org/mail-archive/web/tls/current/msg08722.html https://www.ietf.org/mail-archive/web/tls/current/msg08722.h...

joshAg 14y ago
The issues with bad guys dropping the sig or delaying it also equally applies equally to ssl during the handshake. But waiting for the sig and the whole page to arrive combined wit the size of modern webpages is a problem I hadn't fully considered. I suppose per packet signatures might work to fix the delay issue, but then you'd have to violate abstraction layers and the added cpu time would be completely untenable. At that point you might as well just copy ssl's dh handshake followed by a block cypher but only provide integrity and not privacy, which is stupid. yeah, ok I'm convinced, stupid idea due to practical reasons. just use https with the extra rtt's.
- marshray 14y ago
  It's not a stupid idea, it's a problem that smart folks have been banging their head against for a long time now. Take a look at the "TLS Snap Start" proposal to see the lengths to which one must be willing to go to avoid that round trip. But some low-hanging fruit remains. Improvements to clients and servers that increase TLS session resumption rates would help too.

joshAg 14y ago

The issues with bad guys dropping the sig or delaying it also equally applies equally to ssl during the handshake. But waiting for the sig and the whole page to arrive combined wit the size of modern webpages is a problem I hadn't fully considered. I suppose per packet signatures might work to fix the delay issue, but then you'd have to violate abstraction layers and the added cpu time would be completely untenable. At that point you might as well just copy ssl's dh handshake followed by a block cypher but only provide integrity and not privacy, which is stupid. yeah, ok I'm convinced, stupid idea due to practical reasons. just use https with the extra rtt's.

marshray 14y ago
It's not a stupid idea, it's a problem that smart folks have been banging their head against for a long time now. Take a look at the "TLS Snap Start" proposal to see the lengths to which one must be willing to go to avoid that round trip. But some low-hanging fruit remains. Improvements to clients and servers that increase TLS session resumption rates would help too.