1. ASN.1 소개
건아정보기술
SW개발팀
김강민 주임연구원

2. 목 차 개요
ASN.1 필요성
관련 규범
ASN.1 문법
Basic Encoding Rule(BER)
Q&A

3. 개 요 ASN.1은 Abstract Syntax Notation One의 약자입니다.
국제전기통신 연합(ITU)에서 네트워크 데이터 교환을 정의한 프로토콜로 X.680 ~ X.699에서 정의하고 있습니다.
ASN : Abstract Syntax Notation one. (추상적인 문법 표기 1)
ITU : international Telecommunication Union

4. ASN.1 필요성
Sun과 Windows간 데이터 전송에는 Little endian, Big endian 차이로 인해 데이터 변환이 필요합니다.
1:1이 아니라 N개의 시스템간 통신을 위해서는 이론상 시스템 하나에 N-1개의 데이터 변환기가 필요합니다.
이 부분의 낭비를 줄이기 위해 ASN.1이란 표준을 사용합니다.
ASN.1

5. 관련 규범(1/2)
ISO : Intelligent transport systems (ITS) — Data exchange involving roadside modules communication
ISO
General principles and documentation framework of application profiles
ISO
 Application profile-data exchange (AP-DATEX)
KS X ISO : 교통 정보 및 제어 시스템－ITS를 위한 센터간 데이터 인터페이스
KS X ISO
메시지 정의 요구사항.
KS X ISO
DATEX－ASN
KS X ISO : ISO 문서를 번역해서 기술적 내용 및 규격서의 서식을 변경하지 않고 작성한 한국산업규격이다.

6. 관련 규범 (2/2) ※ ITU 참고사항 (2009년 1월) :
ITU-T ASN.1 Standards Projects Abstract Syntax Notation One
X.680 – Basic Notation
X.681 – Information Objects
X.682 – General Constraint Notation
X.683 – Parameterization
X.690 – Basic (BER), Cannoical(CER), and Distinguished (DER) Encoding Rules
X.691 – Packed Encoding Rules (PER)
Latest
X.692 – Encoding Control Notation (ECN)
X.693 – XML Encoding Rules (XER)

7. ASN.1 문법 (1/10) 예제

8. ASN.1 문법 (2/10) Module Built-in Types Tagged Type assignment
Value assignment
Built-in Types
Simple Type
Structured Type
Tagged

9. ASN.1 문법 (3/10) Module (x.680 - 3.6.43) Module definition
One or more instances of the use of the ASN.1 notation for type, value, value set, information object class, information object, and information object set (as well as the parameterized variant of those), encapsulated using the ASN.1 module notation
Module definition

10. Assignment lexical Item
ASN.1 문법 (4/10)
모듈 분석
Assignment lexical Item
Object Identifier (X.660)
Module definition
Format
Type Assignment
Module Body
Comment (one line)

11. ASN.1 문법 (5/10) Assignment Type Example
InventoryList { } DEFINITIONS ::= BEGIN {
ItemId ::= SEQUENCE
partnumber IA5String,
quantity INTEGER,
wholesaleprice REAL,
saleprice REAL }
StoreLocation ::= ENUMERATED
Baltimore (0),
Philadelphia (1),
Washington (2)
} END

12. ASN.1 문법 (6/10) Assignment Value Example gadget ItemId ::= {
partnumber "7685B2",
quantity 73,
wholesaleprice ,
saleprice }

13. ASN.1 문법 (7/10) Built-in Type Simple type Simple Type Tag Typical use
BOOLEAN 1
Model logical, two-state variable values
INTEGER 2
Model integer variable values
BIT STRING 3
Model binary data of arbitrary length
OCTET STRING 4
Model binary data whose length is a multiple of eight
NULL 5
Indicate effective absence of a sequence element
OBJECT IDENTIFIER 6
Name information objects
REAL 9
Model real variable values
ENUMERATE 10
Model values of variables with at least three states
CHARACTER STRING *
Models values that are strings of characters from a specified characterset
Character Sting Type
Tag
Typical use
NumericString 18
0,1,2,3,4,5,6,7,8,9, and space
PrintableString 19
Upper and lower case letters, digits, space, apostrophe, left/right parenthesis, plus sign, comma, hyphen, full stop, solidus, colon, equal sign, question mark
TeletexString (T61String) 20
The Teletex character set in CCITT's T61, space, and delete
VideotexString 21
The Videotex character set in CCITT's T.100 and T.101, space, and delete
VisibleString (ISO646String) 26
Printing character sets of international ASCII, and space
IA5String 22
International Alphabet 5 (International ASCII)
GraphicString 25
All registered G sets, and space 27
All registered C and G sets, space and delete

14. ASN.1 문법 (8/10) Built-in Type Structured type Structured Type Tag
Typical Use
SEQUENCE 16
Models an ordered collection of variables of different type
SEQUENCE OF
Models an ordered collection of variables of the same type
SET 17
Model an unordered collection of variables of different types
SET OF
Model an unordered collection of variables of the same type
CHOICE *
Specify a collection of distinct types from which to choose one type
SELECTION
Select a component type from a specified CHOICE type
ANY
Enable an application to specify the type Note: ANY is a deprecated ASN.1 Structured Type. It has been replaced with X.680 Open Type.

15. ASN.1 문법 (9/10) Tagged Example a) seats SET {
maximum [APPLICATION 0] INTEGER,
occupied [APPLICATION 1] INTEGER,
vacant [APPLICATION 2] INTEGER }
b) seats SET
maximum [APPLICATION 0] IMPLICIT INTEGER,
occupied [APPLICATION 1] IMPLICIT INTEGER,
vacant [APPLICATION 2] IMPLICIT INTEGER
c) seats SET
maximum [0] INTEGER,
occupied [1] INTEGER,
vacant [2] INTEGER
The APPLICATION class distinguishes data types that have a wide, scattered use within a particular presentation context. PRIVATE distinguishes data types within a particular organization or country. CONTEXT-SPECIFIC distinguishes members of a sequence or set, the alternatives of a CHOICE, or universally tagged set members. Only the class number appears in braces for this data type; the term COONTEXT-SPECIFIC does not appear.

16. ASN.1 문법 (10/10) Lexical Items Comment Range separator : “..”
a "comment" begins with a pair of adjacent hyphens, it shall end with the next pair of adjacent hyphens or at the end of the line.
Ex) // comment one line
a "comment" begins with "/*", it shall end with a corresponding "*/", whether this "*/" is on the same line or not.
Ex) /* comment with several lines */
Range separator : “..”
Assignment lexical item : “::=“
bstring : 0,1로 구성되며 끝에 ‘B를 붙인다.
Ex) ‘ ’B
hstring : 0,1,2..F로 구성되며 끝에 ‘H를 붙인다.
Ex) ‘AB019’H

17. Basic Encoding Rule(BER) (1/5)
The encoding of a data value shall consist of four components which shall appear in the following order
a) identifier octets
b) length octets
c) contents octets
d) end-of-contents octets

18. Basic Encoding Rule(BER) (2/5)
Structure of an encoding
end-of-contents은 반드시 존재해야 하는 것은 아니다.
Identifier octets
Length octets
Contents octets
End-of-contents octets

19. Basic Encoding Rule(BER) (3/5)
Identifier Octet
Length Octet
Short length
the length octets shall consist of a single octet in which bit 8 is zero and bits 7 to 1 encode the number of octets in the contents octets (which may be zero), as an unsigned binary integer with bit 7 as the most significant bit.
L = 38 can be encoded as
Long length
a) bit 8 shall be one;
b) bits 7 to 1 shall encode the number of subsequent octets in the length octets, as an unsigned binary integer with bit 7 as the most significant bit
c) the value shall not be used.
L = 201 can be encoded as:

20. Basic Encoding Rule(BER) (4/5)
Contents octets
The contents octets shall consist of zero, one or more octets, and shall encode the data value as specified
End-of-contents octets
The end-of-contents octets shall be present if the length is encoded as specified

21. Basic Encoding Rule(BER) (5/5)예제
SEQUENCE의 L 부분은 element 인 First와 Second의 길이를 모두 나타낸다.
Seq ::= SEQUENCE {
first INTEGER,
second INTEGER }
seqVa1 Seq ::= { 10, 20 }
Tag
Length
Value
SEQUENCE
V의 길이*
INTEGER
V의 길이 10 20

22. Q & A