BER - Basic Encoding Rules: Introduction

• BER is a simple encoding scheme which works via Type-Length-Value
• Type represents the type of data
• Length represents the length of the data in octets
• Value represents the actual data

Type

• Usually 1 byte
• Bits 6,7 indicate the class. 00=universal; 01=application; 10=context specific; 11=private
• Bit 5 indicates the form; 0=primative; 1=constucted
• Bits 0-4 indicate the Tag or Type of Data

  Hex	Type
  1	boolean
  2	integer
  3	bit string
  4	octet string
  5	null
  6	object identifier
  9	real
  10	sequence of (e.g. array)
  16	iasstring
  1A	visible string

• If all 5 bits of the type are set to 1 indicates a custom type

Length

• 3 ways to encode length
• short, long, indefinite