String (computer science)

About: String (computer science) is a research topic. Over the lifetime, 19430 publications have been published within this topic receiving 333247 citations. The topic is also known as: str & s.

The Status of Orchestra Programs in the Public Schools

Abstract: The objective of this study was to gather descriptive information about orchestra programs that can be used as baseline data when considering the needs of school string programs. Of the 1,345 surve...

Constructing verifiable random functions with large input spaces

Abstract: We present a family of verifiable random functions which are provably secure for exponentially-large input spaces under a noninteractive complexity assumption. Prior constructions required either an interactive complexity assumption or one that could tolerate a factor 2n security loss for n-bit inputs. Our construction is practical and inspired by the pseudorandom functions of Naor and Reingold and the verifiable random functions of Lysyanskaya. Set in a bilinear group, where the Decisional Diffie-Hellman problem is easy to solve, we require the l- Decisional Diffie-Hellman Exponent assumption in the standard model, without a common reference string. Our core idea is to apply a simulation technique where the large space of VRF inputs is collapsed into a small (polynomial-size) input in the view of the reduction algorithm. This view, however, is information-theoretically hidden from the attacker. Since the input space is exponentially large, we can first apply a collision-resistant hash function to handle arbitrarily-large inputs.

TOL systems and languages

Abstract: We discuss a family of systems and languages (called TOL) which have originally arisen from the study of mathematical models for the development of some biological organisms. From a formal language theory point of view, a TOL system is a rewriting system where at each step of a derivation every symbol in a string is rewritten in a context-free way, but different rewriting steps may use different sets of production rules and the language consists of all strings derivable from the single fixed string (the axiom). The family of TOL languages (as well as its different subfamilies considered here) is not closed with respect to usually considered operations; it is “incomparable” with context-free languages, but it is contained in the family of context-free programmed languages. TOL languages form an infinite hierarchy with respect to “natural” complexity measures introduced in this paper.

Cleanness Checking of String Manipulations in C Programs via Integer Analysis

Abstract: All practical C programs use structures, arrays, and/or strings. At runtime, such objects are mapped into consecutive memory locations, hereafter referred to as buffers. Many software defects are caused by buffer overflow -- unintentional access to memory outside the intended object. Stringma nipulation is a major source of such defects. Accordingto the FUZZ study, they are the cause of most UNIX failures. We present a new algorithm for statically detecting buffer overflow defects caused by string manipulations in C programs. In many programs, our algorithm is capable of precisely handling destructive memory updates, even in the presence of overlapping pointer variables which reference the same buffer at different offsets. Thus, our algorithm can uncover defects which go undetected by previous works. We reduce the problem of checkings tring manipulation to that of analyzing integer variables. A prototype of the algorithm has been implemented and applied to statically uncover defects in real C applications, i.e., errors which occur on some inputs to the program. The applications were selected without a priori knowledge of the number of string manipulation errors. A significant number of string manipulation errors were found in every application, further indicating the extensiveness of such errors. We are encouraged by the fact that our algorithm reports very few false alarms, i.e., warnings on errors that never occur at runtime.

Protection of digital content using block cipher crytography

Abstract: Protection of digital content using a specific application of block cipher cryptography is described. The digital content is encrypted using an encryption key and a calculated initialization vector. The digital content includes a plurality of strides of data and each stride includes a string of data to be encrypted and a block of data to be encrypted. The calculated initialization vector to be used to encrypt the block of data is derived from the string of data in the stride to be encrypted. Furthermore, the initialization vector is calculated by performing an exclusive disjunction function on a seed value and the string of data for each stride.