Producción de textos escritos: expresión e interacción

DTN provides security architecture to provide security services for DTN compliant applications. The current security architecture provides the hop-by-hop integrity and authentication and end-to-end integrity, authentication and confidentiality security services. Protection against attacks, like DoS attacks, traffic analysis protection, and key management are still open issues in DTN security [39,40].

The participants in the secure communication in DTN networks are as follows:

• Source - the bundle node which originates bundle.

• Destination - the bundle node to which a bundle is ultimately destined.

• Forwarder - the bundle node that forwards the bundle on its most recent hop

intermediate receiver or next hop. Security Source - The node which applies the security blocks on bundles.

• Security destination - the node which processes all the security blocks on bundles on

behalf of destination.

• Security source and security destination can be different from original source and

destination.

Security block - a block of some fields to add in the bundle which helps in providing the security services in DTN communication. Three types of blocks have been proposed in DTN for authentication (Bundle Authentication Block BAB, integrity (Payload Integrity Block) and confidentiality (Payload Confidentiality Block (PCB). One bundle can include one or more security blocks depending upon the requirements for the network. A security block can be derived from different security suites using symmetric or asymmetric type of cryptography [39,40].

The figure 4-4 shows two DTN nodes BN 1 and BN4 in different networks connected via DTN gateways BN2 and BN3. BNl is a source (the node which originates bundle) which originates

and confidentiality for data. Because, bandwidth is very important resource for DTN type of networks, the architecture allowsintegrity to be validated and it should be ensured that bundle is coming from trusty node, on hop-by-hop basis before forwarding the bundle to next hop and to maximize the throughput by using the feature of store-and-forward communication.

OTIM INI et w o r k

Netw ork Description

S y m b o l 1 C o u n t 1 D e s c r ip tio n : C o m m (Ink ...i...^ C lo u d ; z G a t e w a y ! ^ B u n d le N o d e (BN) B1M 2 B M 3 B N 4 T 1 M l T 1 / T 2 M 1 / M 2 T 1 / T 2 M 1 / M 2 ^ T 2 ^ M 2 . ---- .

Figure 4-4 Heterogeneous networks interconnected via DTN gateways using Bundle Protocol

4.3.5.1 Hop-by-Hop Integrity and Authentication

DTN security architecture supports hop-by-hop integrity validation and authentication. It is to ensure that bundle being forwarded to next hop is not altered and coming from trusted route. As bandwidth is very important resource for DTN type of networks, so this feature is very important in order to take the benefits of store-and-forward custody transfer. In our selected scenario in figure 4-4, the integrity and authentication need to be verified on BN2, BN3 and BN4, thus forming 3 security zones. A security zone is a communication path between a security source (the node which applies the security features) and security destination (the node which verifies the security features). The figure 4-5 shows the hop-by-hop integrity and authentication provision in our selected scenario according to DTN security architecture. DTN suggests making security calculations (e.g. Message Authentication Code) and storing the results in a dedicated security block called “Bundle Authentication Block (BAB)”. This BAB has a place in the blocks stack of bundle protocol and is processed on hop-by-hop basis according to security features selected. More details are available in [40].

r ’

Pr#»$h*p*d Kiev { Public or Symmetnc Key |l

Pre-shaced Key

Pttbilc e»r Sysnmetrte Key )

BN2 Hop -Sectirity Zone 1 Append 8i*ndte Awlhentkatfon Block 0AB)

For data totegrïty and origin aiithoritlcation

for next hop

Pre-sh-ared Key

( Poblk Off SymmeWc Key | K < ^ B N 3

€■

■Security Zone I -

Remove S^B l to verify integrity end aythentication and append BAB2 for

next hop

Pre-shared Key ( Public or Symmetric Key |

BN4

—Hop

Remove SftB l to verify integrity and authentication and append BAF 3 for

next hop BAB (1) Other blocks Stack BAB (2) Other blocks Remove BAB3 to verify Integrity and

authentication

BAB C3)

Other blocks

Figure 4-5: A diagram showing provision of hop-by-hop integrity and authentication features according to DTN security architecture

4.3.5.2 End-to-End Integrity and Authentication

For end-to-end verification of integrity and authentication provision, a separate security block called “Payload Integrity Block (FIB)” is provided by DTN security architecture. FIB stores the calculations results made on data and is available for processing at the security destination. In our selected scenario, for end-to-end integrity and authentication, there is only one security zone as bundle originator is security source and bundle destination is also security destination. The figure 4-6 shows end-to-end integrity and authentication functionality provided in our selected scenario according to DTN security architecture.

P re-shared Key { Public or Sym m etric Key )

Pre-shared Key Public o r Sym m etric Key )

BN2

P re-shared Key ( Public or Sym m etric Key )

BN3 Hop

Append Payload Integrity Block (PIS) For data Integrity and origin authentication

(End-to-End-ish)

Pre-shared Key ( Public or Sym m etric Key )

BN4 Hop

Security Zone 1-

Remove PIB to verify integrity and authentication

r > r A

PIB PIB

Other Other

blocks — Stack Stack — blocks

V J V ....J

Figure 4-6 : A diagram showing provision of end-to-end integrity and authentication features according to DTN security architecture

4.3.5.3 End-to-End Confidentiality

DTN security architecture also provides a confidentiality feature to protect the contents that are not to be disclosed to unauthorized entities on the path from source to destination. A separate security block called “Payload Confidentiality Block (PCB)” is dedicated for this purpose. The results of calculations (e.g. encrypted data) are placed inside the PCB block which can be processed by the security destination to get the original data. For our selected scenario in figure 4-4 , only one security zone exists between source and destination as they are also the security source and security destination. Figure 4-7 shows the PCB working in DTN security architecture. P r e - s h a r e d K ey ( P u b lic o r S y m m e tr ic K ey ) B N l P r e - s h a r e d Key { P u b lic Of S y m m e tr ic Key ) B N 2 H o p P r e - s h a r e d K ey ( P u b lic o r S y m m e t r i c K ey ) B N 3 H o p - S e c u r i ty Z o n e 1 - P r e - s h a r e d Key ( P u b lic o r 5 > ym m etrlc K ey ) B N 4 H o p A p p e n d P a y lo a d C o n f i d e n t i a l i t y B lo c k (PC B ) F o r d a t a c o n f i d e n t i a l i t y ( E n d - to - E n d - is h ) R e m o v e PCB t o g e t o r ig i n a l d a t a s e c u r e l y d e l i v e r e d O t h e r b lo c k s StSCK S t a c k other b lo c k s

'DTN has gained popularity and many articles and papers can be seen in Journals and conference proceedings but, not much effort has put towards security issues in DTN. As Steffen Farrell has pointed out that key management is a very complex and open issue [45]. Based on the literature available [39-45], we have drawn some design guidelines for key management in DTN which are given below.