Non-Repudiation in Internet Telephony

We present a concept to achieve non-repudiation for natural language conversations over the Internet. The method rests on chained electronic signatures applied to pieces of packet-based, digital, voice communication. It establishes the integrity and authenticity of the bidirectional data stream and its temporal sequence and thus the security context of a conversation. The concept is close to the protocols for Voice over the Internet (VoIP), provides a high level of inherent security, and extends naturally to multilateral non-repudiation, e.g., for conferences. Signatures over conversations can become true declarations of will in analogy to electronically signed, digital documents. This enables binding verbal contracts, in principle between unacquainted speakers, and in particular without witnesses. A reference implementation of a secure VoIP archive is exhibited.Comment: Accepted full research paper at IFIP sec2007, Sandton, South Africa, 14-16 May 200

One Asset, Two Prices: The case of the Tsarist Repudiated Bonds

Prices of repudiated bonds are insightful but scarcely observed. Based on an original daily database, this paper compares the price evolution from January 6, 1916 to August 31, 1919 of a cross-listed (Paris and London) Tsarist bond repudiated by the Soviets on February 8, 1918. After its repudiation, the bond exhibits an important geographic price differential. This unusual phenomenon is attributed to the conjunction of war conditions excluding arbitrage and specific investors' expectations regarding bailouts by French and British governments. Furthermore, data from the pre-repudiation period show that the impossibility for arbitrage is not sufficient for driving the pricing differences.bonds, repudiation, sovereign debt, Russia

North-South Lending with Moral Hazard and Repudiation Risk

We show that the joint presence of moral hazard and repudiation risk generates an importnat interaction effect. In order to provide the proper incentives to borrowers, the optimal financial contract under moral hazard calls for all available resources to be paid to the lender in the event of a poor realization for output. Repudiation risk limits the size of this transfer, as the debtor has the option to default. This upper bound on the resource transfer exacerbates the moral hazard problem, reducing lending and the equilibrium level of investment and output.

The ForwardDiffSig scheme for multicast authentication

This paper describes ForwardDiffSig, an efficient scheme for multicast authentication with forward security. This scheme provides source authentication, data integrity, and non-repudiation since it is based on the use of asymmetric cryptography. At the same time, it offers also protection against key exposure as it exploits OptiSum, our optimized implementation of the ISum forward-secure signature scheme. A tradeoff exists in the used keys: Short keys provide speed at the signer, whereas long keys are preferable for long-term non-repudiation. Performance has been evaluated with a custom packet simulator and shows that, by grouping the packets, ForwardDiffSig is efficient in terms of speed even for long keys at the price of a significant signature overhead. Therefore, ForwardDiffSig is fast, exhibits low delay, and provides non-repudiation and protection against key exposure, but has a nonnegligible impact in applications with strict energy or bandwidth constraint

The end of the opportunistic breach of contract! The elective theory of repudiatory breach prevails : Societe Generale, London Branch v Geys [2012] UKSC 63

On the 19th December 2012 the Supreme Court provided an answer to the longstanding question as to the consequences of a wrongfully repudiated contract of employment. Was it for the innocent party to elect to accept the repudiation to bring the contract to an end? Or, was the contract automatically ended upon the wrongful repudiation? Previous authorities had moved between these elective and automatic theories. The elective theory held that a wrongful repudiation only became effective where the innocent party elected to accept the repudiation. Conversely, the automatic theory considered that the contract ended automatically upon the repudiation. Whilst in traditional contract law, the elective theory had been established as effective, this was not decided with authority in contracts of employment. In Geys, the Supreme Court had the opportunity to consider which was the applicable theory in relation to an employer’s use of a payment-in-lieu of notice (PILON) clause. The Court resolved the conflict (4-1 with Lord Sumption dissenting) by holding that the elective theory was preferred in instances of wrongful repudiation of a contract of employment. This judgment has significant implications for employers, but also for employees who wrongfully terminate the contract