Hi Paul,

> On Jun 24, 2016, at 9:43 AM, Paul Wouters <[email protected]> wrote:
> 
> On Fri, 24 Jun 2016, David McGrew wrote:
> 
> Hi David,
> 
>> Because QKD is not a practical system for Internet security.   It has 
>> serious security issues/challenges and operational limitations on bitrate, 
>> range, and physical media.   It requires a point to point optical link, 
>> which is typically dedicated fiber, which must be shorter than 60 miles.  
>> There are security issues with QKD because it relies on a physical 
>> interaction across the line between the encrypter and decrypter, thus giving 
>> an attacker the opportunity to perform an attack on the physical process 
>> anywhere on that line.   See for instance Brassard et. al. Security Aspects 
>> of Practical Quantum Cryptography, Lydersen et. al., Hacking commercial 
>> quantum cryptography systems by tailored bright illumination, or Gerhardt 
>> et. al., Full-field implementation of a perfect eavesdropper on a quantum 
>> cryptography system.   Another major security problem is the range 
>> limitation; it has been proposed to extend the range of QKD by using a chain 
>> of trusted repeaters, each connected by a QKD s
 y
> stem.  These repeaters would greatly increase the attack surface, and require 
> the end user to trust the infrastructure provider(s); in contrast, the 
> Internet community wants end to end encryption, as described in RFC3365 and 
> RFC7624.
>> 
>> In contrast, QR-IKEv2 can be used to add postquantum security between any 
>> two points on the globe, without requiring dedicated fiber, and without 
>> requiring physical layer security assumptions.   It has *fewer* security 
>> assumptions than draft-nagayama-ipsecme-ipsec-with-qkd, as that draft relies 
>> on the security of symmetric cryptography and the physical layer, whereas 
>> QR-IKEv2 relies only on the former.
> 
> For a postquantum IKEv2 extension, does it matter which underlying
> mechanism is used to provide the extra bits to mix into the SKEYSEED?

yes, if identity hiding, efficiency, and incremental deployability matter; 
please see the rationale in Appendix A of 
https://tools.ietf.org/html/draft-fluhrer-qr-ikev2-01.   

thanks

David

> 
> I think what is needed is:
> 
> - A NOTIFY message that signals an identifier of where the extra bits
>  should be taken/generated from. Both endpoints have previous knowledge
>  of what tjos identifier refers to. Be it a hardware device or an
>  offset in a onetime pad, etc, etc.
> 
> - A specification on how to mix in these extra bits into SKEYSEED generation
>  to gain postquantum security.
> 
> - Any additional counter meassures (such as increased minimum keysizes)
> 
> Do we need to know if these bits came from a QKD link, a QR link, or a
> mutually shared onetime pad? If not, then these specifics should not go
> into such an ikev2 extension.
> 
> Paul


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