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 sy
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?

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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