1. Group Key Management Architecture
Howie Weiss
NASA/JPL/SPARTA

2. Types 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

3. We Gotta Get Away From This…
Bank of KW-26s in service from ‘60s – ‘80s.

4. 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

5. IPsec 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)

6. Application 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

7. Conundrums 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

8. 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

9. 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?

10. Group 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 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

11. Group 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

12. GSAKMP 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

13. Group Controller/Key Server
GSAKMP Architecture
Group Owner
Policy
Group Controller/Key Server
[Keys]
Key Infrastructure
Sub GC/KS
Sub GC/KS
Sub GC/KS
Sub GC/KS
Policy & Keys M M M M M M M M

14. Group Trust Group policy vs. Peer Policies
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 strong
As the A to S exchange?
Will A and B protect the data equally?
Is A authorized to distribute key?
Is A controlling the group?
Alice
Bob
A and B have 1st hand knowledge
A and B are sharing their own data
A and B participate in key creation

15. GSAKMP / Group Policy All actors must prove they are authorized
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
DoS controls
Protocol latency controls

16. GSAKMP - Group Joins 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
Member
Member
Member
Member
Member
Member

17. Binary Key Trees A B C D E F 1 2 3 4 5 6 7 8 1,C,A 2,C,A 3,DA 4,DA
1,C,A
2,C,A
3,DA
4,DA
5,E,B
6,E,B
7,F,B
8,F,B

18. Bottom 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.

19. By The Way…..
Cisco is using an alternative group key (GDOI – RFC 3547) to more easily establish VPN groups.