My ASN.1 Notes

Resources

OSS Nokalva Note: I have used OSS Nokalva's ASN.1 Studio and really enjoyed it (UI could use a little love).

Objective Sytems

Power ASN

ETSI ASN.1 Object Identifiers Tree

Mobile Application Part (MAP) CommonDataTypes.asn

Python ASN.1 Resources

Pycrate is a french word for qualifying bad wine. The present software library has nothing to do with bad wine, it is simply a Python library for manipulating various digital formats in an easy way. It is the glorious successor of libmich, which was started 8 years ago and served well.

It provides basically a runtime for encoding and decoding data structures, including CSN.1 and ASN.1. Additionally, it features a 3G and LTE mobile core network.

pyasn1 is a free and open source implementation of ASN.1 types and codecs as a Python package. It has been first written to support particular protocol (SNMP) but then generalized to be suitable for a wide range of protocols based on ASN.1 specification.

asn1ate is a Python library for translating ASN.1 into other forms. It is intended for code generation from formal ASN.1 definitions, and a code generator for pyasn1 is included.

Python-ASN1 is a simple ASN.1 encoder and decoder for Python 2.6+ and 3.3+.

asn1tinydecoder.py is a simple and fast ASN.1 decoder without external libraries designed to parse large files.

Nice examples

Example explaining CHOICE tagging

Example to understand IMPLICIT tagging

TBCD

Telephony Binary-Coded Decimal strings are not part of the ASN.1 standard, but their use is prevalent in many telephony-related ASN.1 specifications.

Conversion of these types into standard numeric text strings is supported by Objective Systems software.

In general, BCD strings pack two numeric digits into a single byte value by using a four-bit nibble to hold each digit. By convention, the digits are reversed in TBCD strings, but there are no official standards for this encoding.

My Notes

Source: ETSI TS 101 671 V3.15.1 (2018-06)

LawfulInterceptionIdentifier ::= OCTET STRING (SIZE (1..25))
-- It is recommended to use ASCII characters in "a"…"z", "A"…"Z", "-", "_", ".", and "0"…"9".
-- For sub-address option only "0"..."9" shall be used.

National-Parameters ::= SET SIZE (1..40) OF OCTET STRING (SIZE (1..256))
-- Content defined by national law.

Network-Identifier ::= SEQUENCE
{
	operator-Identifier [0] OCTET STRING (SIZE (1..5)),
	-- It is a notification of the NWO/AP/SvP in ASCII- characters.
	-- For sub-address option only "0"..."9" shall be used.
	network-Element-Identifier [1] Network-Element-Identifier OPTIONAL,
	...
}

Network-Element-Identifier ::= CHOICE
{
	e164-Format [1] OCTET STRING (SIZE (1..25)),
	-- E164 address of the node in international format. Coded in the same format as the
	-- calling party number parameter of the ISUP (parameter part: EN 300 356 [5]).
	x25-Format [2] OCTET STRING (SIZE (1..25)),
	-- X25 address
	iP-Format [3] OCTET STRING (SIZE (1..25)),
	-- IP address
	dNS-Format [4] OCTET STRING (SIZE (1..25)),
	-- DNS address
	...,
	iP-Address [5] IPAddress
}

TimeStamp ::= CHOICE
{
	localTime [0] LocalTimeStamp,
	utcTime [1] UTCTime
}

LocalTimeStamp ::= SEQUENCE
{
	generalizedTime [0] GeneralizedTime,
	winterSummerIndication [1] ENUMERATED
	{
		notProvided(0),
		winterTime(1),
		summerTime(2),
		...
	}
}

ETSI TS 133 108 v15.7.0 (2020-01)

CC-PDU ::= SEQUENCE
{
	uLIC-header [1] ULIC-header,
	payload [2] OCTET STRING
}

ULIC-header ::= SEQUENCE
{
	hi3DomainId [0] OBJECT IDENTIFIER,
	lIID [2] LawfulInterceptionIdentifier OPTIONAL,
	correlation-Number [3] EPSCorrelationNumber,
	timeStamp [4] TimeStamp OPTIONAL,
	sequence-number [5] INTEGER (0..65535),
	t-PDU-direction [6] TPDU-direction,
	...,
	national-HI3-ASN1parameters [7] National-HI3-ASN1parameters OPTIONAL, -- encoded per national requirements
	ice-type [8] ICE-type OPTIONAL
}

TPDU-direction ::= ENUMERATED
{
	from-target (1),
	to-target (2),
	unknown (3)
}

National-HI3-ASN1parameters ::= SEQUENCE
{
	countryCode [1] PrintableString (SIZE (2)),
	...
}

ICE-type ::= ENUMERATED
{
	sgsn (1),
	ggsn (2),
	...,
	s-GW (3),
	pDN-GW (4),
	colocated-SAE-GWs (5) ,
	ePDG (6)
}

Resources

List of common ASN.1 Types which includes UTCTime and GeneralizedTime in TimeStamp example above.

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