ASN 1 Abstract Syntax Notation One ASN 1

ASN. 1 Abstract Syntax Notation One ASN. 1 is a standard way to describe a message(a unit application data) that can be sent or received in a network. PKI 2001 (TIFR, Mumbai) ASN. 1 is divided into two parts: 1. The rules of syntax for describing the contents of a message in terms of data type and content sequence or structure. 2. How you actually encode each data item in a message. Jump to first page

Why Care about Technical Architecture & Standards? If you want Application Portability You must standardize APIs Implementation Interoperability Protocols Implementation Replaceability All PKI 2001 (TIFR, Mumbai) Jump to first page

ASN. 1 Encoding n n n PKI 2001 (TIFR, Mumbai) Given any ASN. 1 description of a message, a representation can be derived mechanically by applying a set of encoding rules. Initially only a single set, the Basic Encoding Rules(BER), were standardized. Later Canonical and Distinguished Encoding Rules were standardized Jump to first page

Encoding Abstract Values n n PKI 2001 (TIFR, Mumbai) When any (correct) set of encoding rules are applied to the abstract values in any given ASN. 1 type, they will produce bit-patterns (actually octet strings) for each value such that any given octet string corresponds to precisely one abstract value. The reverse is not necessarily true. Jump to first page

ASN. 1 data types n n n PKI 2001 (TIFR, Mumbai) ASN. 1 notation is recognizable as a high level definition language. It is constructed in modules with unique identifiers. There are over 20 built-in identifiers e. g. BOOLEAN, INTEGER, ENUMERATED, REAL, BIT STRING, UTCTime, EXTERNAL, OCTET STRING, NULL etc. Jump to first page

n Arbitrarily complex structures can be built up from these data types using constructors such as : u SET{ } - order not significant u SEQUENCE { } -fixed order one example, PKI 2001 (TIFR, Mumbai) Weather. Report { station. Number time. Of. Report pressure temperature humidity wind. Velocity wind. Direction } : : =SEQUENCE INTEGER(1. . 99999) UTCTime INTEGER(850. . 1100) INTEGER(-100. . 60) INTEGER(0. . 100) INTEGER(0. . 500) INTEGER(0. . 48) Jump to first page

TLV (type-length-value) length - contents) n n PKI 2001 (TIFR, Mumbai) , ILC (identifier - BER generate encodings which are of a class known as type - length value. Now in ASN. 1 they are called as identifier - length - contents. The structure is therefore recursive such that the contents can be a series of ILCs This bottoms out with genuine contents such as a text string or an integer. Jump to first page

Basic Encoding Rules A Schematic Representation PKI 2001 (TIFR, Mumbai) Jump to first page

The use of ASN. 1 Compilers PKI 2001 (TIFR, Mumbai) Jump to first page