Subject: [KEYPROV] New proposal od PSKC schema based on discussions at IETF and terminology alignment

From: "Philip Hoyer" <[email-masked]>
Date: Wed, 8 Apr 2009 17:03:44 +0200

Ladies and Gentlemen,
Please find attached a proposal of the new PSKC schema based on the
discussions at IETF (captured by the email below).

In this first proposal I have tried to reduce the impact of changes to
the current PSKC. Hence there are points that warrant discussion.

Here are the main changes:
1.	Aligned to the concept of Keypackage containing at maximum 1 key
2.	Added the CryptomoduleInfo to Keypackage (introducing an
extensible CryptoModuleInfoType)
3.	Removed the User from the Keypackage and left the User under Key
(I believe having the User under Key is more logical in the sense that
it is the user to whom the key is bound) I thought that at the
Keypackage level it might get confused with the user of the device)
4.	Added a UserId to the DeviceINfo to be still able to convey the
User-> Device Binding 
5.	Renamed the Usage to AlgorithmParameters
6.	Added the missing value for KeyUsage (unwrap, verify, etc)
7.	Removed redundant ref to KeyProperties (in the KeyAttributes)

Since I have tried to minimize the impact on changes currently we have
the following mapping to the concepts discussed at IETF and described in
Pasi's email below:

Key -> PSKC:Key

Key Value -> PSKC:Key.Data(Secret)

Key Attributes -> this is split into more explicit modelled concepts

Example:
	The length of OTP value (for OTP algorithms that support
   	variable length OTPs) -> PSKC:Key.AlgorithmParameters

	date after which the Key should not be used,
   	how access to Key functionality should be controlled (e.g. local
   	PIN code) -> PSKC:Key.Policy

Key Type: this is still split as currently used in PSKS

Determines how a Key works: for example, the allowed lengths
of the Key Value, -> currently determined by PSKC:Key(algorithm)

the cryptographic operations that can be performed
(e.g. OTP computation or challenge-response) -> PSKC.Key.Policy.Usage

Cryptographic Module: ->PSKC:CryptoGraphicModuleInfo

Device: -> PSKC:DeviceInfo

Key Package: -> PSKC:KeyPackage

I believe this is already quite satisfactory.

Now in terms of where in the structure some of these elements sit we can
discuss this further:

I left KeyPolicy under Key so it would be under
<KeyContainer>
	<KeyPackage>
		<Key>
			<Policy>
		</Key>

We can argue if we want to have under the KeyPackage directly:
<KeyContainer>
	<KeyPackage>
		<Key/>
		<Policy/>

I left Issuer under the Key as I logically assume it is the issuer of
the key and not the Issuer of the Device or Cryptomodule.

I introduced CryptoModuleInfo just containing an ID and would like input
on what needs to be added as sub elements.

 <<pskc_080409.xsd>>  <<PSKC_Spec_IETF_PSKC_DRAFT07_Example2.pskc>>  
<<PSKC_Spec_IETF_PSKC_DRAFT03_Example1.pskc>>  
<<PSKC_Spec_IETF_PSKC_DRAFT03_Example3.pskc>>  
<<PSKC_Spec_IETF_PSKC_DRAFT03_Example5.pskc>> 

Please review and comment,

Philip

-----Original Message-----
From: [email-masked] [mailto:[email-masked]] On
Behalf Of Philip Hoyer
Sent: Wednesday, March 25, 2009 9:36 AM
To: [email-masked]; [email-masked]
Subject: Re: [KEYPROV] My notes from today

Pasi,

I think we are getting to some consensus.

I was wondering if Key, KeyAttributes and KeyType need a bit more
analysis.

I believe that we should explicitly model KeyPolicy e.g. the Policy
governing the use of the key, hence this would be:

- Usage (encryption, decription, OTP, etc)
- permitted dates the key can be used
- permitted number of transactions
- PINPoliicy
- etc

Then we have the key and its algorithm

There is the concept of static parameters for a specific algorithm for
example
 - IV 
 - OTP length
 - format produced

And then for some algorithm types we have the concept of dynamic
values/meta_data, tied to a key for example:
 - OTP event counter
 - time drift

Now I am not sure if we need to split them out but currently in PSKC we
have modeled them separately

- dynamic value are under Key.Data (e.g. Key.Data.Counter)
- static values are under Key.Usage (e.g. Key.Usage.ResponseFormat)

The other point I wanted to make is that the User binding currently can
be on a device level AND on a Key level and the Users could be different
so maybe we should leave the user under the respective sub elements:

<KeyContainer>
<KeyPackage>
...info about Key
			Algorithm (under here we could put the current
Key.Usage and rename them as algorithm.parameters)
			Data (dynamic data)
			Policy
			...info about User
			...info about Issuer
...info about Cryptographic Module
...info about Device
			SerialNo
			Manufacturer
			...info about User
			etc
</KeyPackage>
<KeyPackage>
....
</KeyPackage>
<KeyPackage>
....
</KeyPackage>
</KeyContainer>

Philip

-----Original Message-----
From: [email-masked] [mailto:[email-masked]] On
Behalf Of [email-masked]
Sent: Wednesday, March 25, 2009 1:46 AM
To: [email-masked]
Subject: [KEYPROV] My notes from today

Writing these down before the social event... 

Key: A logical component that performs symmetric key operations using
a Key Value, Key Attributes, and other state. 

Key Value: The secret value used by a Key.  (DSKPP and PSKC treat this
as a single key, although there could be some internal structure.)

Key Attributes: Set of information that influence how the Key Value
will be used, and how the Key can be used.

   Example: The length of OTP value (for OTP algorithms that support
   variable length OTPs), date after which the Key should not be used,
   how access to Key functionality should be controlled (e.g. local
   PIN code).

Key Type: Determines how a Key works: for example, the allowed lengths
of the Key Value, the cryptographic operations that can be performed
(e.g. OTP computation or challenge-response) and their inputs,
outputs, and algorithms; and what Key Attributes can be used.

   Example: some examples of one-time password Key Types are HOTP
   [RFC4226], S/Key [RFC1760], and SecurID-AES. In DSKPP and PSKC, 
   Key Types are identified by URIs.

Cryptographic Module: A logical component that contains one or more
Keys. Can be implemented in hardware or software.

Device: The physical device implementing the Cryptographic Module.

   Example: For hardware Cryptographic Modules, a single Device
   usually contains only one Cryptographic Module. For software
   Cryptographic Modules, the Device is the host device (laptop,
   server, mobile phone, etc.), and can contain multiple 
   Cryptographic Modules.

Key Package: A data structure for moving a single Key from one
Cryptographic Module to another. Contains data about the Key (e.g. Key
Value and Attributes), Cryptographic Module (e.g. source or intended
destination Key), Device, Issuer (an organization or party that
manages some Keys -- and possibly Cryptographic Modules and/or Devices
-- or has some kind of authority over them), and User (user, account,
role, or other entity that uses the services provided by Key, or is
otherwise associated with it).
  
Key Container: A data structure or file containing one or more Key
Packages.

These were not discussed, but should be very straightforward:

DSKPP Client: The logical entity implementing the client part of DSKPP
protocol; communicates with an Cryptographic Module to provision Keys
to the Cryptographic Module. In case of Hardware Cryptographic
Modules, the DSKPP Client might run on a PC to which the Hardware
Cryptographic Module is connected.  In case of Software Cryptographic
Modules, the DSKPP Client could be part of the same software package
as the Cryptographic Module itself, or separate.  (The interface
between the Cryptographic Module and the DSKPP Client is not specified
in this document.)

DSKPP Server: The logical entity that communicates with the DSKPP
client; usually communicates with a server-side Cryptographic Module
so that a corresponding Key (with the same Key Value) exists also on
the server side. The interface between the DSKPP Server and the
server-side Cryptographic Module is beyond the scope of this document.

--------------

<KeyContainer>
<KeyPackage>
...info about Key
...info about Cryptographic Module
...info about Device
...info about Issuer
...info about User
</KeyPackage>
<KeyPackage>
....
</KeyPackage>
<KeyPackage>
....
</KeyPackage>
</KeyContainer>

--------

Best regards,
Pasi
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---

From: <[email-masked]>
Date: Mon, 20 Apr 2009 09:21:10 +0200

> (e.g. OTP computation or challenge-response) -> PSKC.Key.Policy.Usage

At least my understanding was that "Key Type" would be a single 
value (URI), and the things currently under Usage (ChallengeFormat,
Encoding, CheckDigit, ...) would all be key attributes. So I'd 
propose just renaming the KeyAlgorithm attribute (in Key) to 
KeyType (we did debate whether this should be called "Key Algorithm",
"Key Type", "Key Class" or something else, and settled on "Key Type").

Splitting the Key Attributes to two places is OK, but for consistency,
they probably should be named AlgorithmAttributes (instead of
AlgorithmParameters -- I think we did discuss whether these should be 
called "Key Attributes" or "Key Parameters" or something else),
and "PolicyAttributes".

But otherwise this looks pretty good!

Best regards,
Pasi