New Single-Trace Side-Channel Attacks on a Specific Class of Elgamal Cryptosystem

In 2005, Yen et al. proposed the first $N-1$ attack on the modular exponentiation algorithms such as BRIP and square-and-multiply-always methods. This attack makes use of the ciphertext $N-1$ as a distinguisher of low order to obtain a strong relation between side-channel leakages and secret exponent. The so-called $N-1$ attack is one of the most important order-2 element attacks, as it requires a non-adaptive chosen ciphertext which is considered as a more realistic attack model compared to adaptive chosen ciphertext scenario. To protect the implementation against $N-1$ attack, several literatures propose the simplest solution, i.e. \textquotedblleft block the special message $N-1$ . In this paper, we conduct an in-depth research on the $N-1$ attack based on the square-and-multiply-always (SMA) and Montgomery Ladder (ML) algorithms. We show that despite the unaccepted ciphertext $N-1$ countermeasure, other types of $N-1$ attacks is applicable to specific classes of Elgamal cryptosystems. We propose new chosen-message power-analysis attacks with order-4 elements which utilize a chosen ciphertext $c$ such that $c^2= -1 \bmod p$ where $p$ is the prime number used as a modulus in Elgamal. Such a ciphertext can be found simply when $p\equiv 1\mod 4$. We demonstrate that ML and SMA algorithms are subjected to our new $N-1$-type attack by utilizing a different ciphertext. We implement the proposed attacks on the TARGET Board of the ChipWhisperer CW1173 and our experiments validate the feasibility and effectiveness of the attacks by using only a single power trace

Can the five-factor model adequately represent the quality-of-life in cancerous patients?

Background: Mental health provides a significant achievement for cancerous patients to alleviate prolonged suffering albeit stress would be the main part of their diseases. Aims: We intend to study the influence of personality dimensions upon cancer patients′ quality-of-life (QOL). Materials and Methods: Short form of NEO Personality Inventory and QOL questionnaire were applied in both descriptive and correlational analyzing. Moreover, the sample group was included 100 patient selected purposefully. Who refer to two medical center of Tehran from April 2012 to March 2013. Participants all fillequestionnaires out. The QOL questionnaire and the short format of NEO personality inventory were used. All of the data were analyzed with Pearson coefficient and multivariate regression analysis. Results: The results indicated that a significant relationship between neuroticism, agreeableness, and QOL was among the patients. Meantime, 23% of variances in quality of lives would be accounted with factors such as neuroticism, agreeableness, extroversion which could significantly predict changes in the patients′ lives. Conclusion: Personality factors are an important variable for the QOL in cancer patients