34 research outputs found
Bit-flipping Decoder Failure Rate Estimation for (v,w)-regular Codes
No full textProviding closed form estimates of the Decoding Failure Rates (DFR) of iterative decoder for low- and moderate-density parity check codes has attracted significant interest in the research community over the years.
This interest has raised due to the use of iterative decoders in post-quantum cryptosystems, where the desired DFRs are impossible to estimate via Monte Carlo simulations.
In this work, we propose a new technique to provide accurate estimates of the DFR of a two-iterations (parallel) bit-flipping decoder, which is also employable for cryptographic purposes.
In doing so, we successfully tackle the estimation of the bit-flipping probabilities at the first and second decoder iteration, and provide a fitting estimate for the syndrome weight distribution.
We numerically validate our results, providing comparisons of the modeled and simulated weight of the syndrome, incorrectly-guessed error bit distribution at the end of the first iteration, and two-iteration DFR, both in the floor and waterfall regime.
Finally, we apply our method to estimate the DFR of LEDAcrypt, a post-quantum cryptosystem, improving by factors larger than 2^{70}, with respect to the previous estimation techniques
Threshold Selection for Iterative Decoding of (v,w)-regular Binary Codes
No full textIterative bit flipping decoders are an efficient and effective choice for decoding codes which admit a sparse parity-check matrix.
Among these, sparse (v,w)-regular codes, which include LDPC and MDPC codes, are of particular interest both for efficient data correction and the design of cryptographic primitives.
Throughout the iterative decoding process, the bit flipping thresholds can be determined either statically or during the decoder execution, by using information coming from the initial syndrome value and its updates.
In this work, we analyze a two-iterations parallel hard decision bit flipping decoder and propose concrete criteria for threshold determination, backed by a closed form model.
In doing so, we introduce a new tightly fitting model for the distribution of the Hamming weight of the syndrome after the first decoder iteration and substantial improvements on the decoding failure rate (DFR) estimation with respect to existing approaches
Infectious aetiology of marginal zone lymphoma and role of anti-infective therapy
No full textMarginal zone lymphomas have been associated with several infectious agents covering both viral and bacterial pathogens and in some cases a clear aetiological role has been established. Pathogenetic mechanisms are currently not completely understood. However, the role of chronic stimulation of the host immune response with persistent lymphocyte activation represents the most convincing explanation for lymphoproliferation. Gastric MALT lymphoma is strictly associated with Helicobacter pylori infection and various eradicating protocols, developed due to increasing antibiotic resistance, represent the first line therapy for gastric MALT. The response rate to eradication is good with 80% of response at 1 year; this finding is also noteworthy because it recapitulates cancer cured only by the antibacterial approach and it satisfies the Koch postulates of causation, establishing a causative relationship between Hp and gastric MALT lymphoma. Patients with chronic HCV infection have 5 times higher risk to develop MZL, in particular, an association with splenic and nodal MZL has been shown in several studies. Moreover, there is evidence of lymphoma regression after antiviral therapy with interferon+ribavirin, thus raising hope that newly available drugs, extremely efficient against HCV replication, could improve outcome also in HCV-driven lymphomas. Another case-study are represented by those rare cases of MZL localized to orbital fat and eye conjunctivas that have been associated with Chlamydophila psittaci infection carried by birds. Efficacy of antibacterial therapy against C. psittaci are conflicting and generally poorer than gastric MALT. Finally, some case reports will cover the relationship between primary cutaneous B-cell Lymphomas and Borrelia Burgdorferi
Closed form decoding failure rate estimation for code-based post-quantum cryptosystems
No full textLAUREA MAGISTRALELa ricerca in Crittografia Post-Quantum ha visto un aumento di interesse, dovuto
ai progressi nello sviluppo di computer quantistici in grado di rompere i
crittosistemi attualmente utilizzati. I crittosistemi basati su codici di
correzione errori costituiscono una valida alternativa, in quanto resistono
ad attacchi classici e quantistici e offrono primitive di comunicazione efficienti.
Alcuni sistemi crittografici basati su codici, come BIKE e LEDAcrypt,
utilizzano un particolare gruppo di codici di correzione errori, chiamati QC-MDPC,
insieme ad algoritmi iterativi a punto fisso per la loro decodifica.
Gli algoritmi di decodifica iterativa utilizzati in questi sistemi hanno una
probabilità non nulla di fallire, e stimare il tasso di fallimento in decodifica
(Decoding Failure Rate, DFR) risulta essere un problema difficile.
I fallimenti in decodifica rivelano informazioni sulla chiave privata dei
crittosistemi, rendendo critica una stima accurata del DFR dei codici utilizzati,
ma la valutazione del tasso di fallimento con simulazioni Monte Carlo è
computazionalmente irrealizzabile per i tassi di errore richiesti (dell'ordine
di 2^-128 o inferiori).
In questa tesi, presentiamo una nuova tecnica per stimare il tasso di fallimento
in decodifica di un decoder parallelo a due e tre iterazioni, offrendo un modello
in forma chiusa per quantificare il DFR di codici crittografici.
Analizziamo la possibilità di utilizzare soglie dipendenti dal valore della sindrome
nell'algoritmo di decodifica, proponendo criteri concreti per la selezione di tali
soglie e la valutazione del loro impatto. Presentiamo un'ampia validazione dei
risultati dei nostri modelli, e quantifichiamo l'impatto di una stima affidabile del
DFR sulle dimensioni dei parametri (chiave pubblica, cifrato) di crittosistemi
post-quantum basati su codici.Post-Quantum Cryptography has seen an increase in interest during the last decades,
due to the advancements in quantum computing research that threatens the security
of current asymmetric encryption methods. Cryptosystems based on Error Correction
Codes prove to be a valid solution, being resistant to classical and quantum
attackers while providing efficient communication primitives.
A particular family of error correction codes, named QC-MDPC codes, have been
employed in code-based post-quantum cryptosystems such as BIKE and LEDAcrypt,
along with iterative decoders.
Iterative bit-flipping decoders lead to a non-zero decoding failure probability,
and estimating the Decoding Failure Rate (DFR) is a crucial yet challenging
task. Indeed, such decoding failures can leak information about the private key,
making accurate DFR estimates critical, and validation via Monte Carlo simulations
is computationally unfeasible for the required failure rates.
In this thesis, we introduce a novel technique to estimate the decoding failure
rate of a two- and three-iterations parallel bit-flipping decoder, offering a
closed form solution for quantifying the DFR of cryptographic-grade codes.
We analyse the possibility of employing syndrome dependent thresholds in the
decoding procedure, proposing concrete criteria for selecting such thresholds
and evaluating their impact. We extensively validate the results of our models,
and quantify the impact of a reliable DFR estimate on code-based post-quantum
cryptosystems
Splenic marginal zone lymphoma: Prognostic factors, role of watch and wait policy, and other therapeutic approaches in the rituximab era
No full textSplenic marginal zone lymphoma (SMZL) is an indolent lymphoma in which watch and wait (W&W) approach as well as splenectomy and chemo-immunotherapy are usually recommended. The role of the different approaches in relation to risk factors was evaluated. One hundred patients with SMZL were retrospectively studied. Median age was 65 years. HCV positivity was 3.1%. The 10-year overall-survival was 95.1% (CI: 90-100%). Sixty-two asymptomatic, low tumour burden patients were submitted to W&W. A low-risk group not requiring treatment was identified. Patients requiring treatment received splenectomy (36), chemotherapy-alone (27) and rituximab ± chemotherapy (16). In multivariate analysis, negative predictors for starting treatment were female-sex, splenomegaly, ECOG ≥ 1. Patients with low IIL-Score had a better 5-year TFT (24%). The median TFT of the W&W cohort was 58.5 months; at 10 years, 17% of patients were still on W&W. Splenectomy and rituximab ± chemotherapy showed similar results, while chemotherapy alone proved inferior. This real-life single-centre study of SMZL confirmed its very good prognosis with a survival likelihood overlapping that of general population. The prognostic role of IIL-Score was confirmed. The W&W approach allowed a median PFS longer than in follicular lymphoma. Finally, our data confirm the inferiority of chemotherapy compared to splenectomy and rituximab ± chemotherapy
Primary uterine localization of malt lymphoma: A case report and literature review
No full text[No abstract available
Spermatogenesis in Hodgkin's lymphoma patients: a retrospective study of semen quality before and after different chemotherapy regimens
No full textIs spermatogenesis impairment caused by Hodgkin's lymphoma (HL) itself or by the various treatments
Efficacy of bendamustine as salvage treatment in an heavily pre-treated Hodgkin lymphoma.
No full textRegression of a case of Multiple Myeloma with antiviral treatment in a patient with chronic HCV infection.
No full textWe report a case of a 54 year old patient with Multiple Myeloma (MM) and chronic HCV infection. In 2005 MM was diagnosed and a chemotherapy was prescribed. Before starting treatment a chronic HCV infection was found. When she came to our Institution for a second opinion, chemotherapy treatment was not considered immediately necessary so the patient was treated for the HCV chronic infection (Pegilated alpha-Interferon 180 μg/week and Ribavirin 1000 mg p.o./day). After one month of treatment she presented a reduction of Bence Jones protein (BJ) that further decreased in the following three months. The antiviral treatment was suspended after six months and a re-evaluation showed a complete viral response and a regression of MM. Sixty-eight months after the end of antiviral treatment the patient is asymptomatic and presents a condition compatible with an M-GUS. While the association between HCV infection and non-Hodgkin's lymphoma is consolidated and it is clearly demonstrated that antiviral treatment in these patients can induce a high proportion of partial and complete remission, a similar effect was never described in MM. The response obtained in our patient may suggest a possible a role of HCV in the pathogenesis of M
The current role of interferon in hairy cell leukaemia: clinical and molecular aspects
No full textWe investigated the current role of interferon-alpha (IFN alpha) in hairy cell leukaemia (HCL) in a retrospective analysis of patients with HCL. A cohort of 74 patients with HCL was divided in to three groups: (A) patients aged >65 years with first-line treatment; (B) patients with comorbidities with first-line treatment; (C) patients who were purine analogues resistant. In total, 94% achieved a response, with a complete response rate of 24%. After a median (range) follow-up of 60 (7-236) months, 55 patients (78%) are still responding. The 5-year progression-free survival was 95%, 68%, and 96% in groups A, B and C respectively. A proportion of patients were monitored through their B-Raf proto-oncogene, serine/threonine kinase (BRAF)-V600E status. IFN alpha remains a possible option in select patients with HCL, where minimal residual disease negativity is achievable
