- From: James M Snell <jasnell@gmail.com>
- Date: Mon, 14 Jan 2013 19:07:42 -0800
- To: Roberto Peon <grmocg@gmail.com>
- Cc: HTTP Working Group <ietf-http-wg@w3.org>
- Message-ID: <CABP7RbdzVuaA0sp+F37+cMehnfKK2qtOSZKMQyKq0xXHpoMRtg@mail.gmail.com>
The randomization is not intended to make reverse engineering impossible, just a large degree more difficult (and potentially more impractical). Used in combination with other strategies -- such as moving away from the use of unauthenticated session ids in cookies -- it could prove effective enough to get the job done. On Mon, Jan 14, 2013 at 7:01 PM, Roberto Peon <grmocg@gmail.com> wrote: > An attacker would run its experiment some increased number of times and > still get information about what is in the context, assuming i am > understanding it correctly. :/ > > -=R > On Jan 14, 2013 5:33 PM, "James M Snell" <jasnell@gmail.com> wrote: > > Just continuing the investigation on various compression strategies. I > spent part of the day going through delta to make sure I understand it and > how it compares with bohe... I'll have some additional thoughts (and > concerns) with regards to that later on... The other half of the day has > been spent with various other bohe variations. Late in the after I hit upon > a particularly interesting variation... I've checked it in here: > https://github.com/jasnell/compression-test/tree/master/compressor/bohe4 > > This variation encodes headers and randomly assigns them to one of two > separate buckets. Those are then randomly ordered and compressed using two > separate compressor instances within the header block... > > # +-------------+--------------------------+ > # | num_headers | block 1 len (4 bytes) | > # +-------------+--------------------------+ > # | compressed header block 1 | > # +----------------------------+-----------+ > # | block 2 len (4 bytes) | | > # +----------------------------+ | > # | compressed header block 2 | > # +----------------------------+-----------+ > > Because of the randomization, there is no way of determining in advance > which block any individual piece of data will land... making it much harder > for an attacker to use the compression ratio to reverse engineer any > particular value... every time the information is sent, it can be in a > different location. You can take the exact same request and encode it > multiple times and end up with a different message size every time (up to a > given limit, of course). > > Some numbers from various test runs... note how bohe4 produces variable > compression ratios given identical input. > > ./compare_compressors.py -c bohe -c bohe4 -c delta -t > /Users/james/git/http_samples/mnot/wikipedia.org.har > 408 req messages processed > compressed | ratio min max std > req bohe 10,784 | 0.13 0.05 0.65 0.07 > req bohe4 13,496 | 0.16 0.05 0.69 0.08 > req delta 16,725 | 0.20 0.04 0.72 0.09 > req http1 84,388 | 1.00 1.00 1.00 0.00 > > 408 res messages processed > compressed | ratio min max std > res bohe 19,882 | 0.25 0.06 0.58 0.10 > res bohe4 20,610 | 0.26 0.09 0.63 0.09 > res delta 24,523 | 0.30 0.04 0.60 0.12 > res http1 80,613 | 1.00 1.00 1.00 0.00 > > ./compare_compressors.py -c bohe -c bohe4 -c delta -t > /Users/james/git/http_samples/mnot/wikipedia.org.har > 408 req messages processed > compressed | ratio min max std > req bohe 10,784 | 0.13 0.05 0.65 0.07 > req bohe4 13,820 | 0.16 0.07 0.67 0.08 > req delta 16,725 | 0.20 0.04 0.72 0.09 > req http1 84,388 | 1.00 1.00 1.00 0.00 > > 408 res messages processed > compressed | ratio min max std > res bohe 19,882 | 0.25 0.06 0.58 0.10 > res bohe4 21,644 | 0.27 0.09 0.61 0.09 > res delta 24,523 | 0.30 0.04 0.60 0.12 > res http1 80,613 | 1.00 1.00 1.00 0.00 > > Again, this is just intended as fodder for discussion right now. I'll have > some comments specifically on delta encoding tomorrow sometime. > > - James > > > On Thu, Jan 10, 2013 at 11:08 AM, James M Snell <jasnell@gmail.com> wrote: > >> I have an initial bohe implementation for the compression tests... it's >> very preliminary and uses the same gzip compression as the current spdy3. >> I'm going to be playing around with the delta compression mechanism as well >> and see how much of an impact that has. Initial results are very promising >> but I haven't done much debugging yet. Just wanted folks to know that this >> work was underway... >> >> https://github.com/jasnell/compression-test/tree/master/compressor/bohe >> >> Some test runs.... >> >> ./compare_compressors.py -c bohe -c spdy3 -c delta >> ../http_samples/mnot/amazon.com.har >> 732 req messages processed >> compressed | ratio min max std >> req bohe 26,122 | 0.13 0.04 0.70 0.08 >> req delta 33,955 | 0.17 0.02 0.71 0.09 >> req http1 195,386 | 1.00 1.00 1.00 0.00 >> req spdy3 27,238 | 0.14 0.04 0.71 0.08 >> >> 732 res messages processed >> compressed | ratio min max std >> res bohe 39,628 | 0.25 0.04 0.66 0.07 >> res delta 44,499 | 0.28 0.02 0.65 0.09 >> res http1 159,968 | 1.00 1.00 1.00 0.00 >> res spdy3 41,325 | 0.26 0.04 0.67 0.08 >> >> >> ./compare_compressors.py -c bohe -c spdy3 -c delta >> ../http_samples/mnot/craigslist.org.har >> 66 req messages processed >> compressed | ratio min max std >> req bohe 1,948 | 0.15 0.06 0.73 0.11 >> req delta 2,036 | 0.16 0.07 0.71 0.11 >> req http1 12,894 | 1.00 1.00 1.00 0.00 >> req spdy3 2,016 | 0.16 0.07 0.75 0.11 >> >> 66 res messages processed >> compressed | ratio min max std >> res bohe 1,786 | 0.18 0.07 0.77 0.13 >> res delta 2,858 | 0.28 0.08 0.69 0.12 >> res http1 10,147 | 1.00 1.00 1.00 0.00 >> res spdy3 1,869 | 0.18 0.09 0.78 0.13 >> >> >> ./compare_compressors.py -c bohe -c spdy3 -c delta >> ../http_samples/mnot/flickr.com.har >> 438 req messages processed >> compressed | ratio min max std >> req bohe 11,988 | 0.10 0.02 0.69 0.07 >> req delta 26,372 | 0.22 0.01 0.71 0.14 >> req http1 121,854 | 1.00 1.00 1.00 0.00 >> req spdy3 12,550 | 0.10 0.02 0.71 0.07 >> >> 438 res messages processed >> compressed | ratio min max std >> res bohe 13,073 | 0.09 0.05 0.66 0.06 >> res delta 25,236 | 0.18 0.02 0.70 0.11 >> res http1 140,457 | 1.00 1.00 1.00 0.00 >> res spdy3 14,142 | 0.10 0.05 0.66 0.06 >> >> >> ./compare_compressors.py -c bohe -c spdy3 -c delta >> ../http_samples/mnot/facebook.com.har >> 234 req messages processed >> compressed | ratio min max std >> req bohe 6,091 | 0.15 0.06 0.78 0.07 >> req delta 7,800 | 0.19 0.02 0.70 0.07 >> req http1 41,980 | 1.00 1.00 1.00 0.00 >> req spdy3 6,301 | 0.15 0.06 0.77 0.07 >> >> 234 res messages processed >> compressed | ratio min max std >> res bohe 9,458 | 0.23 0.07 0.68 0.07 >> res delta 12,045 | 0.30 0.13 0.60 0.08 >> res http1 40,252 | 1.00 1.00 1.00 0.00 >> res spdy3 9,788 | 0.24 0.07 0.69 0.07 >> >> >> >> >> >
Received on Tuesday, 15 January 2013 03:08:30 UTC