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Re: [IPsec] Number of fixed SPI

Paul Wouters <paul@nohats.ca> Sun, 26 March 2017 17:40 UTC

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Date: Sun, 26 Mar 2017 13:40:12 -0400
From: Paul Wouters <paul@nohats.ca>
To: Daniel Migault <daniel.migault@ericsson.com>
cc: IPsecME WG <ipsec@ietf.org>, "lwip@ietf.org" <lwip@ietf.org>
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Subject: Re: [IPsec] Number of fixed SPI
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On Fri, 24 Mar 2017, Paul Wouters wrote:

> On Fri, 24 Mar 2017, Daniel Migault wrote:
>
>> I have a question regarding devices that are not able to randomly generate 
>> SPI, but instead
>> store fix values.  The question is how much fix values could be 
>> provisioned.
>
> This is pretty dangerous. Half a year ago or so we saw the Transcript
> Collsion Attacks that could have succeeded if we hadn't used random
> SPI numbers to prevent pre-calculation in the attack. Using a set of 10
> non-random SPI numbers would potentially make this device vulnerable to
> this attack.

As Tero pointed out to me just now, those were IKE SPI's and not ESP
SPI's to I guess there is no security issue here :)

Paul

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