A survey of survivability in mobile ad hoc networks <s> 1) PGP-like (PL): <s> A pretty bad problem, John Perry Barlow. Part 1 Essential topics: quick overview why do you need GDP? how public key cryptography works installing PGP using PGP managing keys advanced topics beware of snake oil. Part 2 Special topics: useful details setting configuration parameters a peek under the hood vulnerabilities legal issues compatibility with previous and future versions of PGP sources of information on PGP appendix - PGP quick reference. <s> BIB001 </s> A survey of survivability in mobile ad hoc networks <s> 1) PGP-like (PL): <s> In contrast with conventional networks, mobile ad hoc networks usually do not provide online access to trusted authorities or to centralized servers, and they exhibit frequent partitioning due to link and node failures and to node mobility. For these reasons, traditional security solutions that require online trusted authorities or certificate repositories are not well-suited for securing ad hoc networks. We propose a fully self-organized public-key management system that allows users to generate their public-private key pairs, to issue certificates, and to perform authentication regardless of the network partitions and without any centralized services. Furthermore, our approach does not require any trusted authority, not even in the system initialization phase. <s> BIB002 </s> A survey of survivability in mobile ad hoc networks <s> 1) PGP-like (PL): <s> Security poses a major challenge in ad hoc networks today due to the lack of fixed or organizational infrastructure. This paper proposes a modification to the existing "fully distributed certificate authority" scheme for ad hoc networks. In the proposed modification, redundancy is introduced by allocating more than one share to each node in order to increase the probability of creating the certificate for a node in a highly mobile network. A probabilistic analysis is carried out to analyze the trade-offs between the ease of certificate creation and the security provided by the proposed scheme. The analysis carried out from the intruder's perspective suggests that in the worst-case scenario, the intruder is just "one node" away from a legitimate node in compromising the certificate. The analysis also outlines the parameter selection criteria for a legitimate node to maintain a margin of advantage over an intruder in creating the certificate. <s> BIB003
One of the survivable key management initiatives for MANETs is called PGP-like BIB002 . This system handles the public key management problem and proposes a fully distributed self-organizing public key management infrastructure. PGP-like (PL) is based on the PGP (Pretty Good Privacy) functionality BIB001 and each node is responsible for creating its public and private keys. Unlike PGP, where certificates are mainly stored in centralized certificate repositories, certificates in PGP-like are stored, distributed and managed by the nodes in a fully self-organized manner. In this system, key authentication is performed via chains of publickey certificates. As public and private keys are created locally by a node itself, public-key certificates are issued based on the existing trust among the nodes. In this way, if a node x believes that a given public key belongs to a node z, then x can issue publickey certificate in which K z is bound to z by the signature of x. Initially, each node holds in its repository certificates issued by it and the certificates that other nodes issued to it. PGPlike defines a mechanism that provides periodic exchanges of certificates between neighbor nodes. This mechanism aims to distribute the certificates and become more efficient to find a chain of public-key certificates. Moreover, mechanisms to update and to revoke keys are used to prevent conflicts. PGPlike presents also functionalities to deal with misbehavior nodes, such as operations to cross-check the keys in certificates and detect inconsistencies. The certificates are inconsistent when two or more of them are related to the same user, but they present different keys or relate the same public key to different users. 2) Joshi's approach (JA): Joshi et. al propose a fully distributed certificate authority scheme based on secret sharing and redundancy BIB003 . In secret sharing mechanism, the certificate authority's private key is first divided into parts. These parts or key shares are then distributed among the nodes in the network. To communicate, nodes have to recreate the key. The certificate authority (CA) key can be recreated by combining a minimum number of key shares from the total number of shares. The critical situation is when the number of nodes required to recreate the key are not found in the communication range of the node trying to communicate. The number of key shares per node is more than one by incorporating redundancy into the network. Since each node stores more than one key share, then the number of nodes required to recreate the CA key is reduced, increasing the chances of a legitimate node for recreating the CA key. On the other hand, the redundancy poses a challenging since the chances of an intruder entering in the network and compromising the CA key are increased. When an intruder accesses the network and compromises one node, it becomes as good as a valid node. To overcome this problem, it is proposed the use of a intrusion detection system (IDS), which should identify the misbehavior/compromised nodes and remove them from the network. 3) URSA: URSA is a ubiquitous, decentralized, selfcontrolled and robust access control solution for mobile ad hoc networks, where no single node monopolizes the access decision or is assumed to be completely trusted  . Instead, multiple nodes jointly monitor a local node and certify/revoke its ticket. Tickets perform the same functionality of conventional digital certificates, having expiration time, personal public key of the node, signature and identifier. They are certificated and updated periodically to resist conspiracy of attacks by multiple misbehavior nodes. Certifications are based on RSA cryptosystem  and on threshold cryptographybased signature  . URSA handles a localized group trust model where a node is considered trust if it is trusted by a number of reliant nodes. The trust relation is defined within a certain interval limited by the ticket expiration time. Based on this model, trust nodes can sign tickets for all other nodes in the network. These nodes also monitor other nodes in order to detect possible misbehaviors. If a misbehavior node is detected, ticket revocation can be done to prevent the attack propagation. Tickets are also periodically renewed to improve the resilience of the system. Other works follow the same idea of URSA and apply threshold approach as  and  . Although they present similar characteristics to URSA, they deal with a public key management problem. In fact, Zhou and Haas  are the first to address public key management in MANET, and also applied threshold approach to make it decentralized and robust. Table III correlates the initiatives presented in this section with survivability properties. Table IV summarizes the requirements achieved by each survivable initiative and Table V reviews the main techniques applied, the protocol stack layer that is affected, the dependence on a protocol and the attacks addressed by each initiative.