Re: [Ntp] Antw: [EXT] Re: Post NTS, Is shared key authentication interesting?

Harlan Stenn <stenn@nwtime.org> Wed, 27 May 2020 13:46 UTC

Return-Path: <stenn@nwtime.org>
X-Original-To: ntp@ietfa.amsl.com
Delivered-To: ntp@ietfa.amsl.com
Received: from localhost (localhost [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id 7422A3A0ABC for <ntp@ietfa.amsl.com>; Wed, 27 May 2020 06:46:38 -0700 (PDT)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -1.9
X-Spam-Level:
X-Spam-Status: No, score=-1.9 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, SPF_PASS=-0.001, URIBL_BLOCKED=0.001] autolearn=ham autolearn_force=no
Received: from mail.ietf.org ([4.31.198.44]) by localhost (ietfa.amsl.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id I27cPZhaPGAi for <ntp@ietfa.amsl.com>; Wed, 27 May 2020 06:46:35 -0700 (PDT)
Received: from chessie.everett.org (chessie.everett.org [66.220.13.234]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ietfa.amsl.com (Postfix) with ESMTPS id 3C1393A0AB1 for <ntp@ietf.org>; Wed, 27 May 2020 06:46:35 -0700 (PDT)
Received: from [10.208.75.157] (075-139-194-196.res.spectrum.com [75.139.194.196]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits)) (No client certificate requested) by chessie.everett.org (Postfix) with ESMTPSA id 49XBvG6rtXzL7h; Wed, 27 May 2020 13:46:34 +0000 (UTC)
To: ntp@ietf.org
References: <68248D4C020000916A6A8CFC@gwsmtp.uni-regensburg.de> <54A83DA70200003B43047E14@gwsmtp.uni-regensburg.de> <5ECE33E0020000A10003934B@gwsmtp.uni-regensburg.de> <20200527095536.GR2915@roeckx.be> <FAE302D1-126A-4393-9208-8EC1D9F6A7BD@akamai.com> <3c0b465c-69d7-2802-7963-a26d48e9931e@nwtime.org> <F87C6390-9487-4189-934F-E4DC502E3A6A@akamai.com>
From: Harlan Stenn <stenn@nwtime.org>
Autocrypt: addr=stenn@nwtime.org; keydata= mQGNBFI2xmQBDACrPayw18eU4pIwCvKh7k0iMkAV9cvzs49kBppM+xoH+KKj4QWmkKELD39H ngQnT3RkKsTLlwxyLqPdUmeQNAY2M5fsOK+OF6EvwLPK9hbmE3Wx2moX+sbEUxJ2VzFhKSKb OPZALXwk1XxL0qBedz0xHYcDwaSAZZkEFXURv2pDIdrmnoUnq2gdC8GpoFJiXoUaCLSYzzaY ac4Njw7Mue8IqfzRQb70aMjXl/qmsmfmEVAyGXywDdc/ler4XSgiuYOV7Kf69bj9PFZZSMdJ MWgEyZH6lJ0TU5ccR2zp5ZRmWzQQkxJMyH2th7q0Nmz3aX4A0K4yE0Ba9/5Dr7ctpF15BrMF aEo4s5lwI6tUnkgMWo265mMzCz4mAPV/ac0w0OXQg7r9E2r0+dRapnzUlG43D0JLDqDr9uRR L6IrRQqoCWUC75lfmPYQYSlaTJaK68r3lXd0z1cXJUgVtEL5H3/Z71R2B20twcQVAnw2iIH6 L5vdrsIjHrMmkqRVbs9nNyEAEQEAAbQ5SGFybGFuIFN0ZW5uIChOZXR3b3JrIFRpbWUgRm91 bmRhdGlvbikgPHN0ZW5uQG53dGltZS5vcmc+iQG5BBMBAgAjBQJSNsblAhsvBwsJCAcDAgEG FQgCCQoLBBYCAwECHgECF4AACgkQyIwAt1pH+kBlzgv/QOg70vdj8wU/z97UPdlbxtN4THAB gfSX4N0VPKT5fjX1tFhuXZQAOv7wedR3Trh7TGteyg33TBAFf9A42mXZKi1IxAiQG118Hd8I 51rXwnugURIYQaIyQI+vbchRbwVyz+mVLTI/h6FdbsVzT4UFmir+ZMkb/XeZPu0HItk4OZHE 6hk+TuTiCnlqlCPLq371fXV54VOb91WZYD8EQFtK02QHGHsQqWvapdphiDVpYehmsPyiTESq NMKLVtjtyPkQ6S7QF3slSg+2q3j8lyxEA78Yl0MSFNU8B/BtKgzWP2itBOfi+rtUKg+jOY1V /s2uVk2kq2QmHJ/s5k5ldy3qVvoTpxvwBe0+EoBocTHYt+xxp0mTM6YY1xLiQpLznzluqg9z qtejX1gZOF4mgLiBIrhXzed3zsAazhTp5rNb1kn0brZFh6JC5Wk941eilnA4LqX8AWo0lmwo eb+mpwZK/5lNdage/anpVqft9wJ/8EcvST9TLUO4fPrmT3d/0LpWuQGNBFI2xmQBDADXLsBk I7CSa5UXlrNVFJQHER1VxRBKqjWWCh/8Qv9v3p3NrIc2UnhoZ1uWQ2voBGty5Xfy9k4afV5k WwDyRDUIb7PX+Tj4HjVVr7qvnOVe/0KzZpNq0Azd0ggFbsM+8mydktHIwJykW0NUsGwPRYuD OA0Lro0ohb5IiCt3sSQi1X1hYjo7O1Vmn8Gy/XYOnhnMux+5zDPO2yTkCNX5PocYi9IJJy6p Mq1yQV4Y2Dl8KtQzvtq55vCUxx6n0MMzFViGwNW6F4ge9ItO4tDScsgowDrHa208ehwOpv/i wjf93lCClQ6vaKmOBX872K/tdY/hwhxPPjgl1bcrOwMRYVemOPPehwnXH5bwclk1hvDQdkJQ 5pJOkE4VCryTF/iDAt4g2QnHocUwt3b6/ChUUWmj2GZ22OR12rbnCtLedwp0DpViKPUCQHBO vpgXdzE/L9zWar9fqM0EREMgfWbsJc9028qluCcFLIN1gYsq4cC+YGAcOu7HOI5orBBV4m9j XfsAEQEAAYkDPgQYAQIACQUCUjbGZAIbLgGpCRDIjAC3Wkf6QMDdIAQZAQIABgUCUjbGZAAK CRDfCQ/G52/8P/uWDACe7OEM+VETDRqjQgAwzX+RjCVPvtgrqc1SExS0fV7i1mUUxr/B8io3 Y1cRHFoFKmedxf8prHZq316Md5u4egjFdTT6ZqEqkK0hvv+i0pRpCa5EX9VIStcJStomZp8F cY34grA+EOWITaLQ4qNZUP7rf2e7gq1ubQTj7uLr6HZZvMZ5em+IvrOWEuWDI6yOiI6px04w RDfkoR2h6kgdw4V0PT4NjK9WYYKrVCf1bjLlVImNBEcXfvlUTrIYO8y6ptvoUsBQky5pQRvP 99Pn42WfyLy50aII6+vyudD4T0yLjXAz4KteUttxtIte64m/F9/7GEIZAxTUcLyOq/7bP4le h39jBckwc62iYzeK/VkU/bMMh2D68Z3QylMnhhcW27BcgQHPKsHhmFa2SNytYcuQiSdf9+pj 4i32ETz1nJAvYAAqgTF/0PL+8ZNQoEpe/n9woMKrlZrqD4EgFmhQ3bNVhlaXz1nuTZDrwPt1 yMxBuUNbCF4jFnaruwrSiGTRoIfUZQwAjQglahrV4/mcjfnvbNoseHX0PKd9q+wjg7MIjWqr f2CI8Fa6MdanqwYphz43I2yXANKFZuMWsWqyQYlvGuPUlUUcAL3stp24RkzDB1Q+JS0IZJST T2JSu0aTfUdWVNqr2UI19eX+zxbOTckSi3Ng14ezG8ZX194ZH10b8JzntQOwmA20pd5JDhug zQfASER+CZDiPPcQ4mvC4y7rMrfV6XGQbDynC3ekDxo8SC5SvjaczXMwXg6SZ8iFtEWmEwW9 r7zPjjIPDrX8w5LXBgxArM5o/HbERpc2EdAvMh1D7LC0SvmoE7fBKxsicVBe4h6vXjEZ+LLr /wuZiBld9OnxAUIpwptbBspO6WKTQYvgFH2OeDG27hiE5P4Xs4WSp5j9ez8OVB1iZnA2nCQ+ tNTjO8c+C/P92vPLx5+bpGRXTXMNaLh34PS3ZsYoUDkKZNhczRZUWJ7nynSbeeyF+QW7SLwA qY7O7dyk9LFTsfJqRQJ7tWnIAjJPCwmSgQ8Kl0UJ
Message-ID: <a61b31aa-0956-f226-85b2-291c87875e35@nwtime.org>
Date: Wed, 27 May 2020 06:46:33 -0700
User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.8.0
MIME-Version: 1.0
In-Reply-To: <F87C6390-9487-4189-934F-E4DC502E3A6A@akamai.com>
Content-Type: text/plain; charset=utf-8
Content-Language: en-US
Content-Transfer-Encoding: 7bit
Archived-At: <https://mailarchive.ietf.org/arch/msg/ntp/2Dl9Asy68ubxTVleOSncTwAd6zY>
Subject: Re: [Ntp] Antw: [EXT] Re: Post NTS, Is shared key authentication interesting?
X-BeenThere: ntp@ietf.org
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: <ntp.ietf.org>
List-Unsubscribe: <https://www.ietf.org/mailman/options/ntp>, <mailto:ntp-request@ietf.org?subject=unsubscribe>
List-Archive: <https://mailarchive.ietf.org/arch/browse/ntp/>
List-Post: <mailto:ntp@ietf.org>
List-Help: <mailto:ntp-request@ietf.org?subject=help>
List-Subscribe: <https://www.ietf.org/mailman/listinfo/ntp>, <mailto:ntp-request@ietf.org?subject=subscribe>
X-List-Received-Date: Wed, 27 May 2020 13:46:39 -0000


On 5/27/2020 6:41 AM, Salz, Rich wrote:
>     > This is known as an oracle, and from this kind of thing, it is possible to do pretty fine-grain timings and figure out keys.  This is often surprising to folks, but look up "Lucky Thirteen" as an example. 
> 
>>    So where is this attacker?
> 
> On the network.  Anywhere on the Internet.
> 
> Maybe for this case it doesn't matter (I am not convinced), but it is worth reinforcing as a design principle.

I think one could easily implement a bad system where this would be a
problem.

In the normal use-case and with a "normal" implementation, I'm not
seeing how this can be a problem.  I'm open to seeing that I'm missing
something, however.

-- 
Harlan Stenn <stenn@nwtime.org>
http://networktimefoundation.org - be a member!