Android mobile devices have been suffering from performance degradation and increased failure rates during long-term operation, known as software aging. With the major changes in performance optimization and resource management in Android, it is spotted that the aging behavior of Android devices in the 2020s differs significantly from previous studies in resource utilization and performance metrics, which makes some classic metrics difficult to measure aging well, and new metrics are required to better describe the new phenomenon. Thus, we propose thread- and interface-level metrics to portray aging at a finer granularity and conduct an empirical study to reidentify classic and new software aging metrics in Android. Analysis confirms that software aging in Android is less reflected in global resources metrics but in more fine-grained ones, so thread- and interface-level metrics combined with specific classic resource and process-level metrics are helpful as indicators of software aging. These metrics have been confirmed and deployed for aging monitoring by our mobile phone manufacturer collaborators. A new experimental method customized for metric studies has also been adopted in this paper, significantly reducing data costs and interference in measurements.

With the popularity of vehicular ad-hoc networks (VANETs), the secure communications between the vehicle and vehicle as well as between the vehicle and infrastructure have attracted people’s great attention. Vehicle privacy protection (including vehicle identity privacy and location privacy), high mobility, density, and limited bandwidth are also a problem that cannot be negligible. In VANETs, it is necessary to design a message authentication protocol to ensure data transmission security, vehicle anonymity, and unlinkability. Considering the resource-constrained environments, the certificateless aggregate signature (CLAS) scheme can compress$n$signatures of$n$messages from$n$vehicles into a single signature, which reduces the signature verification time and storage overhead at the roadside unit. Based on the aforementioned analysis, we design a fully aggregated conditional privacy-preserving CLAS scheme (CPP-CLAS) for VANETs. Instead of using the expensive bilinear pairings and map-to-point hash function operations, the proposed CPP-CLAS scheme uses the elliptic curve cryptosystem (ECC) and general hash functions. Also, with the use of CLAS technology, the computation and communication cost of the scheme are significantly reduced. In addition, based on the elliptic-curve discrete logarithm problem (ECDLP), we prove that the CPP-CLAS scheme is existential unforgeability under adaptively chosen message attacks (EUF-CMAs). Performance and security analyses show that the CPP-CLAS scheme is more efficient and secure than other existing related schemes.