On debugging in a parallel system

In this paper a description is given of a partly implemented parallel debugger for the Twente University Multicomputer (TUMULT). The system's basic method for exchange of data is message passing. Experience has learned that most programming errors in application software are made in calls to the kernel and the interprocess communication. The debugger is intended to be used for locating bugs at this level in the application software. It is assumed that basic blocks of the debuggee can be debugged using a traditional sequential sourcelevel debugger

Digital Signatures for PTP Using Transparent Clocks

Smart grids use synchronous real-time measurements from phasor measurement units (PMU) across portions of a grid to provide grid-wide integrity. Achieving synchronicity requires either accurate GPS clocks at each PMU or a high-resolution clock synchronization protocol, such as the Precision Time Protocol (PTP), specified in IEEE 1588 with the power profile in IEEE C37.238-2011. PTP does not natively include measures to provide authenticity or integrity for timestamps transmitted across an Ethernet network, though there has been recent work in providing end-to-end integrity of transmitted timestamps. However, PTP for use in the smart grid requires a version of the protocol in which network switches update the trusted timestamp in flight, meaning that an end-to-end approach is no longer sufficient. We propose two methods to provide for the integrity of the transmitted and updated timestamps as well as to ensure the authority of all network devices altering the time. In the first, we amend the PTP standard to include signatures as part of the time packet itself at the cost of increased jitter in the system. In the second, we transmit these signatures over a wireless network, reducing congestion on the original network. We test both methods on a simulated PTP switch intended for experimentation only and demonstrate that the use of a second network dedicated to verification-related information is better for current networks, as including signatures in the original packet causes more jitter than is acceptable for synchronizing PMUs in particular

Digital Signatures for PTP Using Transparent Clocks

Smart grids use synchronous real-time measurements from phasor measurement units (PMU) across portions of a grid to provide grid-wide integrity. Achieving synchronicity requires either accurate GPS clocks at each PMU or a high-resolution clock synchronization protocol, such as the Precision Time Protocol (PTP), specified in IEEE 1588 with the power profile in IEEE C37.238-2011. PTP does not natively include measures to provide authenticity or integrity for timestamps transmitted across an Ethernet network, though there has been recent work in providing end-to-end integrity of transmitted timestamps. However, PTP for use in the smart grid requires a version of the protocol in which network switches update the trusted timestamp in flight, meaning that an end-to-end approach is no longer sufficient. We propose two methods to provide for the integrity of the transmitted and updated timestamps as well as to ensure the authority of all network devices altering the time. In the first, we amend the PTP standard to include signatures as part of the time packet itself at the cost of increased jitter in the system. In the second, we transmit these signatures over a wireless network, reducing congestion on the original network. We test both methods on a simulated PTP switch intended for experimentation only and demonstrate that the use of a second network dedicated to verification-related information is better for current networks, as including signatures in the original packet causes more jitter than is acceptable for synchronizing PMUs in particular

Cryptographic timestamping through Sequential Work

We present a definition of an ideal timestamping functionality that maintains a timestamped record of bitstrings. The functionality can be queried to certify the record and the age of each entry at the current time. An adversary can corrupt the timestamping functionality, in which case the adversary can output its own certifications of the record and age of entries under strict limitations. Most importantly, the adversary initially cannot falsify any part of the record, but the maximum age of entries the adversary can falsify grows linearly over time. We introduce a single-prover non-interactive cryptographic timestamping protocol based on proofs of sequential work. The protocol securely implements the timestamping functionality in the random-oracle model and universal-composability framework against an adversary that can compute proofs of sequential work faster by a certain factor. Because of the computational effort required, such adversaries have the same strict limitations under which they can falsify the record as under the ideal functionality. This protocol trivially extends to a multi-prover protocol where the adversary can only generate malicious proofs when it has corrupted at least half of all provers. As an attractive feature, we show how any party can efficiently borrow proofs by interacting with the protocol and generate its own certification of records and their ages with only a constant loss in age. The security guarantees of our timestamping protocol only depend on how long ago the adversary corrupted parties and on how fast honest parties can compute proofs of sequential work relative to an adversary, in particular these guarantees are not affected by how many proofs of sequential work honest or adversarial parties run in parallel