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The security of electronic networks and information systems is nowadays seen as a critical issue for the growth of Information and Communication Technologies. Cryptographic protocols are used to provide security services such as confidentiality, message integrity, authentication, certified E-mail and non-repudiation. Traditionally, security protocols have been designed and verified using informal techniques. However, the absence of formal verification can lead to security errors remaining undetected. Formal verification techniques provide a systematic way of discovering protocol flaws. This paper establishes a freshness flaw in a keydistribution and Authentication Protocol using an automated logic-based verification engine. The performed verification reveals a freshness flaw in the protocol that allows an intruder to impersonate legitimate principals. The cause of the freshness flaw is discussed and an amended protocol is proposed. Formal verification of the amended protocol provides confidence in the correctness and effectiveness of the proposed modifications.

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Many peer-to-peer security protocols proposed for wireless communications use one-time shared secrets for authentication purposes. This paper analyses online update mechanisms for one-time shared secrets. A new type of attack against update mechanisms, called desynchronisation attack, is introduced. This type of attack may lead to a permanent denial of service condition. A case study demonstrates the effectiveness of desynchronisation attacks against a security protocol for mobile satellite communications. A new mutual authentication protocol for satellite communications, incorporating a resynchronisation capability, is proposed to counter the disruptive effects of desynchronisation attacks. The new protocol has an esynchronisation phase that is initiated whenever desynchronisation is suspected. Thus, the possibility of causing permanent denial of service conditions by mounting desynchronisation attacks is eliminated. A security analysis of the proposed protocol establishes its resistance against attacks like replay attacks, dictionary attacks, and desynchronisation attacks.

Many peer-to-peer security protocols proposed for wireless communications use one-time shared secrets for authentication purposes. This paper analyses online update mechanisms for one-time shared secrets. A new type of attack against update mechanisms, called desynchronisation attack, is introduced. This type of attack may lead to a permanent denial of service condition. A case study demonstrates the effectiveness of desynchronisation attacks against a security protocol for mobile satellite communications. A new mutual authentication protocol for satellite communications, incorporating a resynchronisation capability, is proposed to counter the disruptive effects of desynchronisation attacks. The new protocol has an esynchronisation phase that is initiated whenever desynchronisation is suspected. Thus, the possibility of causing permanent denial of service conditions by mounting desynchronisation attacks is eliminated. A security analysis of the proposed protocol establishes its resistance against attacks like replay attacks, dictionary attacks, and desynchronisation attacks.