1. Bruno Saba DCT/TV/IN 26/04/2010
Space Data Link Secure Protocol Interoperability Testing Interfaces Definition Proposal
Bruno Saba
DCT/TV/IN
26/04/2010

2. Interfaces between two distant simulators
Data Interfaces
Connecting one or more « useful » data stream
TC or Forward link(s)
TM or Return link(s)
Control Interfaces
Used for exchange of data relative to the simulators’ management
« Synchronisation » data
Simulation starting time …
Others
Simulator results
Files for comparison
SDLS - Interoperability Testing - Interfaces Definition Proposal CNES B. Saba

3. CNES’ Proposals 1st step of Interoperability Testing
Main goal : KEEP IT SIMPLE !
The objective is to validate the protocol, not to build a complex network system
Use UDP/IP for data streams
TC or Forward Link
TM or Return Link
UDP/IP is a well defined and well known protocol
No need for special hardware or software
Easy to implement
No flow control, some packets can be lost (like in the « real life » of the protocol)
Can be used on-line between two distant simulators, or off-line on localhost
Already used in CNES’ simulator
SDLS - Interoperability Testing - Interfaces Definition Proposal CNES B. Saba

4. CNES’ Proposals 1st step of Interoperability Testing (cont’d)
On-line or Off-line simulations
On-line : direct communication via UDP/IP
Off-line : exchange of files
Use s or telephone for control data
Simulations Starting time / Ending time scheduled by s
File exchange by
Transfer of data files for comparison purposes
Transfer of simulation results
Use of phone if needed…
Use of TCP/IP for synchronisation purposes only on the 2nd step, only if needed
SDLS - Interoperability Testing - Interfaces Definition Proposal CNES B. Saba

5. What do we need to agree on ?
Interfaces between simulators (easy…)
UDP/IP for data
s or phone for control
First implementation of the SDLS protocol ! (not so easy…)
SDLS protocol baseline
Secure services (authentication, encryption, authenticated encryption)
Algorithm(s) and modes of operation
Security Association / Security Context convergence… DONE
Position of Security Layer (TC Link) DONE
Security header definition DONE
Security header position DONE …
SDLS - Interoperability Testing - Interfaces Definition Proposal CNES B. Saba

6. First implementation of the SDLS protocol
Services provided
Clear mode
Authentication only (AO) (TC,TM)
Authenticated Encryption (AE) (TC,TM)
Encryption Only (EO) (TM Only)
No switching management between services
Algorithms and modes of operation (same algorithms for TC and TM)
AES GMAC (for AO)
AES GCM (for AE)
AES CTR (for EO)
No special Key Management
Exchange of Keys between two simulators before simulation session
No Security Association Dynamic Management
Agreement on the content of the SA to be used before simulation
SDLS - Interoperability Testing - Interfaces Definition Proposal CNES B. Saba

7. First implementation of the SDLS protocol
TC link (or Forward link)
Transmission of the complete CLTU ?
Including Start Sequence (EB90) and Tail Sequence
This would allow future testing of hardware implementation of the protocol
COP-1 Implementation ?
May be useful to see possible interaction between COP-1 and SDLSP…
Position of Security Header
Just after the Transfer Frame Primary Header (as defined in W1 Nov 2009)
SDLS - Interoperability Testing - Interfaces Definition Proposal CNES B. Saba

8. First implementation of the SDLS protocol
TC link (cont’d)
Security Header Definition
Sequence Number : not needed, Initialization Vector and Authentication service providing anti-replay protection
Initialization Vector : 4 Bytes
Key Index : not needed for TC link
PAD length : not needed
Security Header total length : 6 Bytes
Trailer (Message Authentication Code) length : 16 Bytes
SDLS - Interoperability Testing - Interfaces Definition Proposal CNES B. Saba

9. First implementation of the SDLS protocol
TC link (cont’d)
Security Association Definition
Each Security Association must contain
Global MAPID(s) to which it is assigned
Service provided (Clear, AO, AE)
Key
Initialisation Vector Management
4 byte counter
Generated by the ground segment
On-board control mecanism : new received IV must be greater than the previous one
Guarantees IV uniqueness
Also provides anti-replay service
SDLS - Interoperability Testing - Interfaces Definition Proposal CNES B. Saba

10. First implementation of the SDLS protocol
TM link (or Return link)
Transmission of the complete CADU ?
Including Start Sequence (1ACFFC1D) and Tail Sequence
This would allow future testing of hardware implementation of the protocol
Position of Security Header
Just after Frame Secondary Header (if present) (as defined in W1 Nov 2009)
SDLS - Interoperability Testing - Interfaces Definition Proposal CNES B. Saba

11. First implementation of the SDLS protocol
TM link (cont’d)
Security Header Definition
Sequence Number :
Not needed if Encryption Only mode is not used, Initialization Vector and Authentication service providing anti-replay protection
When using EO mode, counter on IV provides anti replay protection
Initialization Vector : 6 Bytes ?
Key Index : 2 Bytes
PAD length : not needed
Security Header total length : 10 Bytes
Message Authentication Code (trailer) : 16 Bytes
SDLS - Interoperability Testing - Interfaces Definition Proposal CNES B. Saba

12. First implementation of the SDLS protocol
TM link (cont’d)
Security Association Definition
Each Security Association must contain
Global Virtual Channel(s) to which it is assigned
Service provided (Clear, AO, AE, EO)
Key set (key selection by key index)
Initialisation Vector Management
6 byte counter
Generated on-board
On-board generation guarantees no regression : new IV sent is greater than the previous one (+1)
Guarantees IV uniqueness
Also provides anti-replay service
SDLS - Interoperability Testing - Interfaces Definition Proposal CNES B. Saba

13. Conclusion
Development of the simulators can start as soon as everybody agrees on the first implementation of the SDLS Protocol
Interoperability Testing would then begin step by step
TM Link
TC Link (no COP-1)
TM Link and TC Link
TM Link and TC Link with COP-1
SDLS - Interoperability Testing - Interfaces Definition Proposal CNES B. Saba

14. Thank you for your attention
SDLS - Interoperability Testing - Interfaces Definition Proposal CNES B. Saba