# Cryptographic Key Management in Delay Tolerant Networks: A Survey
## 3 Key Management Taxonomy in DTNs
### Standardisation Efforts  
Until now, a handful of Internet drafts have been released regarding security and key management in DTN, but no full-fledged solution is yet proposed. In [28; 58] the authors states a series of requirements for key management in DTNs without proposing a solution. In fact, in RFC6257 [39] and in Internet draft [59] key management is recognized as a cumbersome topic and the authors explicitly state that such exclusion is a result of an informed decision. The BSP specification [39] defines security features for the BP [4] and attempts to protect its operation by introducing security mechanisms that provide confidentiality, integrity, and bundle authentication. More specifically, it describes four security blocks to cater for different security services. These blocks, namely the BAB, the PIB, the PCB and the Extensions Security Block (ESB), are defined in the Abstract Security Block (ASB). The Consultative Committee for Space Data Systems (CCSDS) released a green book [60] about key management concept in space environments, where they described the basics for the CCSDS standardization activities related to security services and key management schemes for space missions. In addition, an internet draft about DTN security services is given in [59], where the Streamlined Bundle Security Protocol (SBSP) is introduced. Specifically, SBSP is an improvement and simplification on BSP and provides authentication, integrity, and confidentiality for the \"bundles\" along the transmission path. It combines BSB with Bundle-in-Bundle encapsulation (BIBE) and supports three security blocks, namely BAB, BIB and BCB. As expected, SBSP applies only to security-aware nodes. More recently, the DTN Networking Security Key Management [61] and DTN Security Key Management [62] have been released. The former states the key management problem in DTNs and emphasizes that traditional security key management mechanisms are not always feasible in environments where DTN typically operate in. The latter proposes requirements and presents a design for key management in DTNs. Specifically, the core requirements and design criteria for DTN security key management are described. The newly published Internet draft [63] defines the DTN key management problem and at the same time provides high-level solutions for public key distribution and public key revocation. Finally, the Bundle Protocol Security Specification (BPSec) [64] defines a security protocol for the services of end-to-end data integrity and confidentiality of the BP. Table 6 summarizes all the security-related Internet drafts and RFCs.  
\begin{table}
\begin{tabular}{l l l l} \hline
**Title** & **Naming Conventions** & **Released Date** & **Expiration Date** \\ \hline DTN Key Management Requirements [58] & draft-farrell-dtrng-km-00 & June 2007 & December 2007 \\ \hline Delay-Tolerant Networking Security Overview [28] & draft-irtf-dtrng-sec-overview-06 & March 2009 & September 2009 \\ \hline Bundle Security Protocol Specification [39] & RFC6257 & May 2011 & - \\ \hline Space Mission Key Management Concept [60] & CCSDS 350.6-G-1 & November 2011 & - \\ \hline Delay Tolerant Networking Security Key Management - Problem Statement [61] & draft-templim-dtnskmps-00 & March 2014 & September 2014 \\ \hline Stream Expanded Bundle Security Protocol Specification [59] & draft-if-dtrng-gksp-01 & May 2014 & November 2014 \\ \hline DTN Security Key Management - Requirements and Design [62] & draft-templim-dtnskmps-00 & February 2015 & August 2015 \\ \hline Architecture for a Delay-and-Disruption Tolerant Public-Key Distribution Network (PKDN) [63] & draft-viswanathan-dtrng-p-bkdn-00 & August 2015 & February 2016 \\ \hline Bundle Protocol Security Specification [64] & draft-ietf-dtn-bpsec-04 & March 2017 & September 2017 \\ \hline \end{tabular}
\end{table}
Table 6: Security-related internet drafts and RFCs.