Sepucha_Date_01

Group Key Management ArchitectureGroup Key Management Architecture

Howie WeissNASA/JPL/SPARTAhsw@sparta.com

Sepucha_Date_02

Types of Key ManagementTypes of Key Management

• Manual key generation & distribution– Hardcopy, paper tape, key cards, floppy disks,

magnetic tape– Hand carried and manually loaded

• Electronic key generation & distribution– EKMS (electronic key management system)

» LMD/KP (local KPs, dial-up to download keys)» KDC (e.g., STU-III Central Facility, STU-II Bellfield)

• Public Key– Key agreements between key pairs

» Public/private key negotiation to establish symmetric key

• Group Key– Generate, distribute, manage keys and policies for a

group of systems

Sepucha_Date_03

We Gotta Get Away From This…We Gotta Get Away From This…

Bank of KW-26s in service from ‘60s – ‘80s.

Sepucha_Date_04

A Bit Better ….A Bit Better ….

•Key order processing•Electronic generation & dist•FIREFLY generation•Seed Key conversion•CRL•OTAR

•Central Office of Record•Phys key dist•Elect key dist•Key generation•Key ordering

•KOK-22 Key Processor•Local key generation•Digital signature

•KYK-13•KOI-18•CYZ-10•New fill devices

Sepucha_Date_05

IPsec RequirementsIPsec Requirements

• IPsec “lives” between the network (IP) layer and transport (TCP or UDP) layer

• Requires a “security policy database” to determine what services are applied to what connections

– E.g., connection A-B requires encryption+auth– E.g., connection C-D requires encryption– E.g., all other connections require no security services

• Crypto keys – Manually loaded, or– IKEv2 negotiated

• Policy:– Manually loaded in each individual device, or

» RFC 4807 (IPsec Security Policy Database Configuration MIB)

» IPsec Security Policy IPsec Action MIB (ID)» IPsec Security Policy IKE Action MIB (ID)

Sepucha_Date_06

Application Layer SecurityApplication Layer Security

• A la SSL/TLS (but TBD)• Requires keys

– SSL/TLS would use Diffie-Helman key negotiation which may not be possible for Cx flight systems.

– Pre-shared symmetric keys a la RFC 4279.» e.g., TLS_PSK_WITH_AES_128_CBC_SHA

• Requires policy– SSL/TLS really has no policy database– “https” == encrypt connection– Mutual authentication (dual cert) vs. server-side

authentication (single cert)• Messaging security

– Pub/Sub messaging security mechanims

Sepucha_Date_07

ConundrumsConundrums

• Keys are required by heterogeneous systems• Policy is required by heterogeneous systems• Ground/Mission systems have good, broadband

connectivity• Space systems may have intermittent, lossy, and

limited bandwidth connectivity

Sepucha_Date_08

So…..So…..

• Public Key technology and Electronic Key Distribution are the ‘modern’ ways to generate and distribute keys, but…….

– Not a problem for ground-based systems with good connectivity

– Can be a problem for space-based systems with not so good connectivity

Sepucha_Date_09

Therefore…..Therefore…..

• How do we combine ‘modern’ electronic key distribution with varying types of connectivity across the entire program?

– 1) go with PKI and hope for the best (a la cellular phone systems)?

– 2) use only PKI in control centers and do something else for space?

– 3) use symmetric keys everywhere and deliver them manually (e.g., floppy, flash drive, paper tape)?

– 4) LMD/KP local site generation and manual loading?– 5) Central key distribution center (KDC) that all systems

must contact to obtain keys?– 6) ‘Group keying’ techniques doing what’s best and

available for the given part of the system?

Sepucha_Date_010

Group Key OverviewGroup Key Overview

• From RFC 2094:– “GKMP combines techniques developed for creation of

pair-wise keys with techniques used to distribute keys from a KDC (i.e., symmetric encryption of keys) to distribute symmetric key to a group of hosts.”

• Defined in RFC 4535 - GSAKMP: Group Secure Association Key Management Protocol

– Parameters for a given GSAKMP group are provided in the Group Security Policy Token, whose structure is defined in RFC 4534

Sepucha_Date_011

Group SecurityGroup Security

• Use of cryptography to protect data shared between multiple endpoints

– Encryption of data» Network layer» Application layer

– Key management for groups» Definition of mutual suspicious key exchanges for groups» Security policy and policy dissemination» Key creation and dissemination

– Security management for groups» Scalability of security infrastructure» Coalitions and diverse mechanisms» Low latency group establishment» Management of group membership

Sepucha_Date_012

GSAKMP EntitiesGSAKMP Entities

• Group Owner – responsible for creating the security policy rules for a group

and expressing these in the policy token• Group Controller/Key Server

– responsible for creating/obtaining keys, maintaining the keys, and enforcing the group policy by granting access to potential Group Members (GMs) in accordance with the policy token

– In a distributed mode, there can be multiple subordinate GC/KSs

• Group Member– responsible for verifying key and policy disseminations and

for protecting group data according to group policy

Sepucha_Date_013

GSAKMP ArchitectureGSAKMP Architecture

Group Owner

Group Controller/Key

Server

Sub GC/KS

Sub GC/KS

Sub GC/KS

Sub GC/KS

M M M M M M M M

Key Infrastructure

Policy[Keys]

Policy & Keys

Sepucha_Date_014

Group Trust Group Trust Group policy vs. Peer PoliciesGroup policy vs. Peer Policies

Alice Bob

•A and B have 1st hand knowledge

•A and B are sharing their own data

•A and B participate in key creation

Alice Bob

Sue ?

•A and B have 1st hand knowledge•A and S have 1st hand knowledge•B and S have never communicated

•Who owns the data?•How can S trust B? B trust S?•Was the A to B key exchange as strongAs the A to S exchange?•Will A and B protect the data equally?•Is A authorized to distribute key?•Is A controlling the group?

Sepucha_Date_015

GSAKMP / Group PolicyGSAKMP / Group Policy

• Must support mutual suspicion– All actors must prove they are authorized

» Policy creation authorities» Key dissemination» Key possession» Group management

• Must provide flexible group definitions– Rule based access control

» Limited only by infrastructures available– Mechanism flexibility

» Algorithms» Infrastructures» Protocols

– Operational flexibility» Group management» DoS controls» Protocol latency controls

Sepucha_Date_016

GSAKMP - Group JoinsGSAKMP - Group Joins

GroupController

MemberMember

Member

Member

• Group Controller– Defines group policy– Creates initial keys

• Members join the group– Can become subordinate GCs– Can be key consumers

• Member can get keys from GC or S-GC• Group membership is managed using

group cryptography– One message can reconfigure

membership of receivers

MemberMember

MemberMember

MemberMember

MemberMember

Member

Member

Member

Member

Sepucha_Date_017

Binary Key TreesBinary Key Trees

1 2 3 4 5 6 7 8

A B

C D E F

1,C,A 2,C,A 3,DA 4,DA 5,E,B 6,E,B 7,F,B 8,F,B

Sepucha_Date_018

Bottom LineBottom Line

• GSAKMP can provide key and policy management for scalable groups (large or small).

• Group members can perform a full, negotiated group join or can just receive keys from a group or sub-group controller

• Combines the best of public key, symmetric key, and policy management.

• Can provide keys (with work on the host side) to applications, IPsec (using multicast SAs), and even bulk encryptors if they can be controlled by the system.

Sepucha_Date_019

By The Way…..By The Way…..

• Cisco is using an alternative group key (GDOI – RFC 3547) to more easily establish VPN groups.