draft-ietf-cbor-7049bis-04.txt		draft-ietf-cbor-7049bis-05.txt
	Network Working Group C. Bormann		Network Working Group C. Bormann
	Internet-Draft Universitaet Bremen TZI		Internet-Draft Universitaet Bremen TZI
	Intended status: Standards Track P. Hoffman		Intended status: Standards Track P. Hoffman
	Expires: April 26, 2019 ICANN		Expires: July 19, 2019 ICANN
	October 23, 2018		January 15, 2019
	Concise Binary Object Representation (CBOR)		Concise Binary Object Representation (CBOR)
	draft-ietf-cbor-7049bis-04		draft-ietf-cbor-7049bis-05
	Abstract		Abstract
	The Concise Binary Object Representation (CBOR) is a data format		The Concise Binary Object Representation (CBOR) is a data format
	whose design goals include the possibility of extremely small code		whose design goals include the possibility of extremely small code
	size, fairly small message size, and extensibility without the need		size, fairly small message size, and extensibility without the need
	for version negotiation. These design goals make it different from		for version negotiation. These design goals make it different from
	earlier binary serializations such as ASN.1 and MessagePack.		earlier binary serializations such as ASN.1 and MessagePack.
	Contributing		Contributing
	skipping to change at page 1, line 47 ¶		skipping to change at page 1, line 47 ¶
	Internet-Drafts are working documents of the Internet Engineering		Internet-Drafts are working documents of the Internet Engineering
	Task Force (IETF). Note that other groups may also distribute		Task Force (IETF). Note that other groups may also distribute
	working documents as Internet-Drafts. The list of current Internet-		working documents as Internet-Drafts. The list of current Internet-
	Drafts is at https://datatracker.ietf.org/drafts/current/.		Drafts is at https://datatracker.ietf.org/drafts/current/.
	Internet-Drafts are draft documents valid for a maximum of six months		Internet-Drafts are draft documents valid for a maximum of six months
	and may be updated, replaced, or obsoleted by other documents at any		and may be updated, replaced, or obsoleted by other documents at any
	time. It is inappropriate to use Internet-Drafts as reference		time. It is inappropriate to use Internet-Drafts as reference
	material or to cite them other than as "work in progress."		material or to cite them other than as "work in progress."
	This Internet-Draft will expire on April 26, 2019.		This Internet-Draft will expire on July 19, 2019.
	Copyright Notice		Copyright Notice
	Copyright (c) 2018 IETF Trust and the persons identified as the		Copyright (c) 2019 IETF Trust and the persons identified as the
	document authors. All rights reserved.		document authors. All rights reserved.
	This document is subject to BCP 78 and the IETF Trust's Legal		This document is subject to BCP 78 and the IETF Trust's Legal
	Provisions Relating to IETF Documents		Provisions Relating to IETF Documents
	(https://trustee.ietf.org/license-info) in effect on the date of		(https://trustee.ietf.org/license-info) in effect on the date of
	publication of this document. Please review these documents		publication of this document. Please review these documents
	carefully, as they describe your rights and restrictions with respect		carefully, as they describe your rights and restrictions with respect
	to this document. Code Components extracted from this document must		to this document. Code Components extracted from this document must
	include Simplified BSD License text as described in Section 4.e of		include Simplified BSD License text as described in Section 4.e of
	the Trust Legal Provisions and are provided without warranty as		the Trust Legal Provisions and are provided without warranty as
	described in the Simplified BSD License.		described in the Simplified BSD License.
	Table of Contents		Table of Contents
	1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3		1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4
	1.1. Objectives . . . . . . . . . . . . . . . . . . . . . . . 4		1.1. Objectives . . . . . . . . . . . . . . . . . . . . . . . 4
	1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 5		1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 6
	2. CBOR Data Models . . . . . . . . . . . . . . . . . . . . . . 7		2. CBOR Data Models . . . . . . . . . . . . . . . . . . . . . . 7
	2.1. Extended Generic Data Models . . . . . . . . . . . . . . 8		2.1. Extended Generic Data Models . . . . . . . . . . . . . . 8
	2.2. Specific Data Models . . . . . . . . . . . . . . . . . . 8		2.2. Specific Data Models . . . . . . . . . . . . . . . . . . 9
	3. Specification of the CBOR Encoding . . . . . . . . . . . . . 9		3. Specification of the CBOR Encoding . . . . . . . . . . . . . 9
	3.1. Major Types . . . . . . . . . . . . . . . . . . . . . . . 10		3.1. Major Types . . . . . . . . . . . . . . . . . . . . . . . 10
	3.2. Indefinite Lengths for Some Major Types . . . . . . . . . 11		3.2. Indefinite Lengths for Some Major Types . . . . . . . . . 12
	3.2.1. Indefinite-Length Arrays and Maps . . . . . . . . . . 12		3.2.1. The "break" Stop Code . . . . . . . . . . . . . . . . 12
	3.2.2. Indefinite-Length Byte Strings and Text Strings . . . 14		3.2.2. Indefinite-Length Arrays and Maps . . . . . . . . . . 12
			3.2.3. Indefinite-Length Byte Strings and Text Strings . . . 14
	3.3. Floating-Point Numbers and Values with No Content . . . . 15		3.3. Floating-Point Numbers and Values with No Content . . . . 15
	3.4. Optional Tagging of Items . . . . . . . . . . . . . . . . 16		3.4. Optional Tagging of Items . . . . . . . . . . . . . . . . 16
	3.4.1. Date and Time . . . . . . . . . . . . . . . . . . . . 18		3.4.1. Date and Time . . . . . . . . . . . . . . . . . . . . 18
	3.4.2. Standard Date/Time String . . . . . . . . . . . . . . 18		3.4.2. Standard Date/Time String . . . . . . . . . . . . . . 18
	3.4.3. Epoch-based Date/Time . . . . . . . . . . . . . . . . 18		3.4.3. Epoch-based Date/Time . . . . . . . . . . . . . . . . 18
	3.4.4. Bignums . . . . . . . . . . . . . . . . . . . . . . . 19		3.4.4. Bignums . . . . . . . . . . . . . . . . . . . . . . . 19
	3.4.5. Decimal Fractions and Bigfloats . . . . . . . . . . . 20		3.4.5. Decimal Fractions and Bigfloats . . . . . . . . . . . 20
	3.4.6. Content Hints . . . . . . . . . . . . . . . . . . . . 21		3.4.6. Content Hints . . . . . . . . . . . . . . . . . . . . 21
	3.4.6.1. Encoded CBOR Data Item . . . . . . . . . . . . . 21		3.4.6.1. Encoded CBOR Data Item . . . . . . . . . . . . . 21
	3.4.6.2. Expected Later Encoding for CBOR-to-JSON		3.4.6.2. Expected Later Encoding for CBOR-to-JSON
	Converters . . . . . . . . . . . . . . . . . . . 21		Converters . . . . . . . . . . . . . . . . . . . 22
	3.4.6.3. Encoded Text . . . . . . . . . . . . . . . . . . 22		3.4.6.3. Encoded Text . . . . . . . . . . . . . . . . . . 22
	3.4.7. Self-Describe CBOR . . . . . . . . . . . . . . . . . 22		3.4.7. Self-Described CBOR . . . . . . . . . . . . . . . . . 23
	4. Creating CBOR-Based Protocols . . . . . . . . . . . . . . . . 23		4. Creating CBOR-Based Protocols . . . . . . . . . . . . . . . . 23
	4.1. CBOR in Streaming Applications . . . . . . . . . . . . . 24		4.1. CBOR in Streaming Applications . . . . . . . . . . . . . 24
	4.2. Generic Encoders and Decoders . . . . . . . . . . . . . . 24		4.2. Generic Encoders and Decoders . . . . . . . . . . . . . . 24
	4.3. Syntax Errors . . . . . . . . . . . . . . . . . . . . . . 25		4.3. Syntax Errors . . . . . . . . . . . . . . . . . . . . . . 25
	4.3.1. Incomplete CBOR Data Items . . . . . . . . . . . . . 25		4.3.1. Incomplete CBOR Data Items . . . . . . . . . . . . . 25
	4.3.2. Malformed Indefinite-Length Items . . . . . . . . . . 25		4.3.2. Malformed Indefinite-Length Items . . . . . . . . . . 26
	4.3.3. Unknown Additional Information Values . . . . . . . . 26		4.3.3. Unknown Additional Information Values . . . . . . . . 26
	4.4. Other Decoding Errors . . . . . . . . . . . . . . . . . . 26		4.4. Other Decoding Errors . . . . . . . . . . . . . . . . . . 26
	4.5. Handling Unknown Simple Values and Tags . . . . . . . . . 27		4.5. Handling Unknown Simple Values and Tags . . . . . . . . . 27
	4.6. Numbers . . . . . . . . . . . . . . . . . . . . . . . . . 27		4.6. Numbers . . . . . . . . . . . . . . . . . . . . . . . . . 27
	4.7. Specifying Keys for Maps . . . . . . . . . . . . . . . . 28		4.7. Specifying Keys for Maps . . . . . . . . . . . . . . . . 28
	4.7.1. Equivalence of Keys . . . . . . . . . . . . . . . . . 29		4.7.1. Equivalence of Keys . . . . . . . . . . . . . . . . . 29
	4.8. Undefined Values . . . . . . . . . . . . . . . . . . . . 30		4.8. Undefined Values . . . . . . . . . . . . . . . . . . . . 30
	4.9. Preferred Serialization . . . . . . . . . . . . . . . . . 30		4.9. Preferred Serialization . . . . . . . . . . . . . . . . . 30
	4.10. Canonical CBOR . . . . . . . . . . . . . . . . . . . . . 31		4.10. Canonically Encoded CBOR . . . . . . . . . . . . . . . . 31
	4.10.1. Length-first map key ordering . . . . . . . . . . . 33		4.10.1. Length-first map key ordering . . . . . . . . . . . 33
	4.11. Strict Mode . . . . . . . . . . . . . . . . . . . . . . . 34		4.11. Strict Decoding Mode . . . . . . . . . . . . . . . . . . 34
	5. Converting Data between CBOR and JSON . . . . . . . . . . . . 35		5. Converting Data between CBOR and JSON . . . . . . . . . . . . 35
	5.1. Converting from CBOR to JSON . . . . . . . . . . . . . . 35		5.1. Converting from CBOR to JSON . . . . . . . . . . . . . . 36
	5.2. Converting from JSON to CBOR . . . . . . . . . . . . . . 37		5.2. Converting from JSON to CBOR . . . . . . . . . . . . . . 37
	6. Future Evolution of CBOR . . . . . . . . . . . . . . . . . . 37		6. Future Evolution of CBOR . . . . . . . . . . . . . . . . . . 38
	6.1. Extension Points . . . . . . . . . . . . . . . . . . . . 38		6.1. Extension Points . . . . . . . . . . . . . . . . . . . . 38
	6.2. Curating the Additional Information Space . . . . . . . . 39		6.2. Curating the Additional Information Space . . . . . . . . 39
	7. Diagnostic Notation . . . . . . . . . . . . . . . . . . . . . 39		7. Diagnostic Notation . . . . . . . . . . . . . . . . . . . . . 39
	7.1. Encoding Indicators . . . . . . . . . . . . . . . . . . . 40		7.1. Encoding Indicators . . . . . . . . . . . . . . . . . . . 40
	8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 41		8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 41
	8.1. Simple Values Registry . . . . . . . . . . . . . . . . . 41		8.1. Simple Values Registry . . . . . . . . . . . . . . . . . 41
	8.2. Tags Registry . . . . . . . . . . . . . . . . . . . . . . 41		8.2. Tags Registry . . . . . . . . . . . . . . . . . . . . . . 42
	8.3. Media Type ("MIME Type") . . . . . . . . . . . . . . . . 42		8.3. Media Type ("MIME Type") . . . . . . . . . . . . . . . . 42
	8.4. CoAP Content-Format . . . . . . . . . . . . . . . . . . . 42		8.4. CoAP Content-Format . . . . . . . . . . . . . . . . . . . 43
	8.5. The +cbor Structured Syntax Suffix Registration . . . . . 43		8.5. The +cbor Structured Syntax Suffix Registration . . . . . 43
	9. Security Considerations . . . . . . . . . . . . . . . . . . . 44		9. Security Considerations . . . . . . . . . . . . . . . . . . . 44
	10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 44		10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 45
	11. References . . . . . . . . . . . . . . . . . . . . . . . . . 45		11. References . . . . . . . . . . . . . . . . . . . . . . . . . 45
	11.1. Normative References . . . . . . . . . . . . . . . . . . 45		11.1. Normative References . . . . . . . . . . . . . . . . . . 45
	11.2. Informative References . . . . . . . . . . . . . . . . . 46		11.2. Informative References . . . . . . . . . . . . . . . . . 46
	Appendix A. Examples . . . . . . . . . . . . . . . . . . . . . . 48		Appendix A. Examples . . . . . . . . . . . . . . . . . . . . . . 48
	Appendix B. Jump Table . . . . . . . . . . . . . . . . . . . . . 52		Appendix B. Jump Table . . . . . . . . . . . . . . . . . . . . . 52
	Appendix C. Pseudocode . . . . . . . . . . . . . . . . . . . . . 55		Appendix C. Pseudocode . . . . . . . . . . . . . . . . . . . . . 55
	Appendix D. Half-Precision . . . . . . . . . . . . . . . . . . . 57		Appendix D. Half-Precision . . . . . . . . . . . . . . . . . . . 57
	Appendix E. Comparison of Other Binary Formats to CBOR's Design		Appendix E. Comparison of Other Binary Formats to CBOR's Design
	Objectives . . . . . . . . . . . . . . . . . . . . . 58		Objectives . . . . . . . . . . . . . . . . . . . . . 58
	E.1. ASN.1 DER, BER, and PER . . . . . . . . . . . . . . . . . 59		E.1. ASN.1 DER, BER, and PER . . . . . . . . . . . . . . . . . 59
	skipping to change at page 9, line 51 ¶		skipping to change at page 10, line 15 ¶
	The meaning of this argument depends on the major type. For example,		The meaning of this argument depends on the major type. For example,
	in major type 0, the argument is the value of the data item itself		in major type 0, the argument is the value of the data item itself
	(and in major type 1 the value of the data item is computed from the		(and in major type 1 the value of the data item is computed from the
	argument); in major type 2 and 3 it gives the length of the string		argument); in major type 2 and 3 it gives the length of the string
	data in bytes that follows; and in major types 4 and 5 it is used to		data in bytes that follows; and in major types 4 and 5 it is used to
	determine the number of data items enclosed.		determine the number of data items enclosed.
	If the encoded sequence of bytes ends before the end of a data item		If the encoded sequence of bytes ends before the end of a data item
	would be reached, that encoding is not well-formed. If the encoded		would be reached, that encoding is not well-formed. If the encoded
	sequence of bytes still has bytes remaining after the outermost		sequence of bytes still has bytes remaining after the outermost
	encoded item is parsed, that encoding is not a single well-formed		encoded item is decoded, that encoding is not a single well-formed
	CBOR item.		CBOR item.
	A CBOR decoder implementation can be based on a jump table with all		A CBOR decoder implementation can be based on a jump table with all
	256 defined values for the initial byte (Table 5). A decoder in a		256 defined values for the initial byte (Table 5). A decoder in a
	constrained implementation can instead use the structure of the		constrained implementation can instead use the structure of the
	initial byte and following bytes for more compact code (see		initial byte and following bytes for more compact code (see
	Appendix C for a rough impression of how this could look).		Appendix C for a rough impression of how this could look).
	3.1. Major Types		3.1. Major Types
	skipping to change at page 12, line 5 ¶		skipping to change at page 12, line 17 ¶
	Four CBOR items (arrays, maps, byte strings, and text strings) can be		Four CBOR items (arrays, maps, byte strings, and text strings) can be
	encoded with an indefinite length using additional information value		encoded with an indefinite length using additional information value
	31. This is useful if the encoding of the item needs to begin before		31. This is useful if the encoding of the item needs to begin before
	the number of items inside the array or map, or the total length of		the number of items inside the array or map, or the total length of
	the string, is known. (The application of this is often referred to		the string, is known. (The application of this is often referred to
	as "streaming" within a data item.)		as "streaming" within a data item.)
	Indefinite-length arrays and maps are dealt with differently than		Indefinite-length arrays and maps are dealt with differently than
	indefinite-length byte strings and text strings.		indefinite-length byte strings and text strings.
	3.2.1. Indefinite-Length Arrays and Maps		3.2.1. The "break" Stop Code
	Indefinite-length arrays and maps are simply opened without		The "break" stop code is encoded with major type 7 and additional
	indicating the number of data items that will be included in the		information value 31 (0b111_11111). It is not itself a data item: it
	array or map, using the additional information value of 31. The		is just a syntactic feature to close an indefinite-length item.
	initial major type and additional information byte is followed by the
	elements of the array or map, just as they would be in other arrays		If the "break" stop code appears anywhere where a data item is
	or maps. The end of the array or map is indicated by encoding a		expected, other than directly inside an indefinite-length string,
	"break" stop code in a place where the next data item would normally		array, or map -- for example directly inside a definite-length array
	have been included. The "break" is encoded with major type 7 and		or map -- the enclosing item is not well-formed.
	additional information value 31 (0b111_11111) but is not itself a
	data item: it is just a syntactic feature to close the array or map.		3.2.2. Indefinite-Length Arrays and Maps
	That is, the "break" stop code comes after the last item in the array
	or map, and it cannot occur anywhere else in place of a data item.		Indefinite-length arrays and maps are represented using their major
	In this way, indefinite-length arrays and maps look identical to		type with the additional information value of 31, followed by an
			arbitrary-length sequence of items for an array or key/value pairs
			for a map, followed by the "break" stop code (Section 3.2.1). In
			other words, indefinite-length arrays and maps look identical to
	other arrays and maps except for beginning with the additional		other arrays and maps except for beginning with the additional
	information value 31 and ending with the "break" stop code.		information value of 31 and ending with the "break" stop code.
	Arrays and maps with indefinite lengths allow any number of items		If the break stop code appears after a key in a map, in place of that
	(for arrays) and key/value pairs (for maps) to be given before the		key's value, the map is not well-formed.
	"break" stop code. There is no restriction against nesting
	indefinite-length array or map items. A "break" only terminates a		There is no restriction against nesting indefinite-length array or
	single item, so nested indefinite-length items need exactly as many		map items. A "break" only terminates a single item, so nested
	"break" stop codes as there are type bytes starting an indefinite-		indefinite-length items need exactly as many "break" stop codes as
	length item.		there are type bytes starting an indefinite-length item.
	For example, assume an encoder wants to represent the abstract array		For example, assume an encoder wants to represent the abstract array
	[1, [2, 3], [4, 5]]. The definite-length encoding would be		[1, [2, 3], [4, 5]]. The definite-length encoding would be
	0x8301820203820405:		0x8301820203820405:
	83 -- Array of length 3		83 -- Array of length 3
	01 -- 1		01 -- 1
	82 -- Array of length 2		82 -- Array of length 2
	02 -- 2		02 -- 2
	03 -- 3		03 -- 3
	skipping to change at page 14, line 15 ¶		skipping to change at page 14, line 29 ¶
	0xbf6346756ef563416d7421ff		0xbf6346756ef563416d7421ff
	BF -- Start indefinite-length map		BF -- Start indefinite-length map
	63 -- First key, UTF-8 string length 3		63 -- First key, UTF-8 string length 3
	46756e -- "Fun"		46756e -- "Fun"
	F5 -- First value, true		F5 -- First value, true
	63 -- Second key, UTF-8 string length 3		63 -- Second key, UTF-8 string length 3
	416d74 -- "Amt"		416d74 -- "Amt"
	21 -- Second value, -2		21 -- Second value, -2
	FF -- "break"		FF -- "break"
	3.2.2. Indefinite-Length Byte Strings and Text Strings		3.2.3. Indefinite-Length Byte Strings and Text Strings
	Indefinite-length byte strings and text strings are actually a		Indefinite-length strings are represented by a byte containing the
	concatenation of zero or more definite-length byte or text strings		major type and additional information value of 31, followed by a
	("chunks") that are together treated as one contiguous string.		series of byte or text strings ("chunks") that have definite lengths,
	Indefinite-length strings are opened with the major type and		followed by the "break" stop code (Section 3.2.1). The data item
	additional information value of 31, but what follows are a series of		represented by the indefinite-length string is the concatenation of
	byte or text strings that have definite lengths (the chunks). The		the chunks.
	end of the series of chunks is indicated by encoding the "break" stop
	code (0b111_11111) in a place where the next chunk in the series
	would occur. The contents of the chunks are concatenated together,
	and the overall length of the indefinite-length string will be the
	sum of the lengths of all of the chunks. In summary, an indefinite-
	length string is encoded similarly to how an indefinite-length array
	of its chunks would be encoded, except that the major type of the
	indefinite-length string is that of a (text or byte) string and
	matches the major types of its chunks.
	For indefinite-length byte strings, every data item (chunk) between		If any item between the indefinite-length string indicator
	the indefinite-length indicator and the "break" MUST be a definite-		(0b010_11111 or 0b011_11111) and the "break" stop code is not a
	length byte string item; if the parser sees any item type other than		definite-length string item of the same major type, the string is not
	a byte string before it sees the "break", it is an error.		well-formed.
			If any definite-length text string inside an indefinite-length text
			string is invalid, the indefinite-length text string is invalid.
			Note that this implies that the bytes of a single UTF-8 character
			cannot be spread between chunks: a new chunk can only be started at a
			character boundary.
	For example, assume the sequence:		For example, assume the sequence:
	0b010_11111 0b010_00100 0xaabbccdd 0b010_00011 0xeeff99 0b111_11111		0b010_11111 0b010_00100 0xaabbccdd 0b010_00011 0xeeff99 0b111_11111
	5F -- Start indefinite-length byte string		5F -- Start indefinite-length byte string
	44 -- Byte string of length 4		44 -- Byte string of length 4
	aabbccdd -- Bytes content		aabbccdd -- Bytes content
	43 -- Byte string of length 3		43 -- Byte string of length 3
	eeff99 -- Bytes content		eeff99 -- Bytes content
	FF -- "break"		FF -- "break"
	After decoding, this results in a single byte string with seven		After decoding, this results in a single byte string with seven
	bytes: 0xaabbccddeeff99.		bytes: 0xaabbccddeeff99.
	skipping to change at page 15, line 5 ¶		skipping to change at page 15, line 14 ¶
	5F -- Start indefinite-length byte string		5F -- Start indefinite-length byte string
	44 -- Byte string of length 4		44 -- Byte string of length 4
	aabbccdd -- Bytes content		aabbccdd -- Bytes content
	43 -- Byte string of length 3		43 -- Byte string of length 3
	eeff99 -- Bytes content		eeff99 -- Bytes content
	FF -- "break"		FF -- "break"
	After decoding, this results in a single byte string with seven		After decoding, this results in a single byte string with seven
	bytes: 0xaabbccddeeff99.		bytes: 0xaabbccddeeff99.
	Text strings with indefinite lengths act the same as byte strings
	with indefinite lengths, except that all their chunks MUST be
	definite-length text strings. Note that this implies that the bytes
	of a single UTF-8 character cannot be spread between chunks: a new
	chunk can only be started at a character boundary.
	3.3. Floating-Point Numbers and Values with No Content		3.3. Floating-Point Numbers and Values with No Content
	Major type 7 is for two types of data: floating-point numbers and		Major type 7 is for two types of data: floating-point numbers and
	"simple values" that do not need any content. Each value of the		"simple values" that do not need any content. Each value of the
	5-bit additional information in the initial byte has its own separate		5-bit additional information in the initial byte has its own separate
	meaning, as defined in Table 1. Like the major types for integers,		meaning, as defined in Table 1. Like the major types for integers,
	items of this major type do not carry content data; all the		items of this major type do not carry content data; all the
	information is in the initial bytes.		information is in the initial bytes.
	+-------------+--------------------------------------------------+		+------------+------------------------------------------------------+
	| 5-Bit Value | Semantics |		| 5-Bit | Semantics |
	+-------------+--------------------------------------------------+		| Value | |
	| 0..23 | Simple value (value 0..23) |		+------------+------------------------------------------------------+
	| | |		| 0..23 | Simple value (value 0..23) |
	| 24 | Simple value (value 32..255 in following byte) |		| | |
	| | |		| 24 | Simple value (value 32..255 in following byte) |
	| 25 | IEEE 754 Half-Precision Float (16 bits follow) |		| | |
	| | |		| 25 | IEEE 754 Half-Precision Float (16 bits follow) |
	| 26 | IEEE 754 Single-Precision Float (32 bits follow) |		| | |
	| | |		| 26 | IEEE 754 Single-Precision Float (32 bits follow) |
	| 27 | IEEE 754 Double-Precision Float (64 bits follow) |		| | |
	| | |		| 27 | IEEE 754 Double-Precision Float (64 bits follow) |
	| 28-30 | (Unassigned) |		| | |
	| | |		| 28-30 | (Unassigned) |
	| 31 | "break" stop code for indefinite-length items |		| | |
	+-------------+--------------------------------------------------+		| 31 | "break" stop code for indefinite-length items |
			| | (Section 3.2.1) |
			+------------+------------------------------------------------------+
	Table 1: Values for Additional Information in Major Type 7		Table 1: Values for Additional Information in Major Type 7
	As with all other major types, the 5-bit value 24 signifies a single-		As with all other major types, the 5-bit value 24 signifies a single-
	byte extension: it is followed by an additional byte to represent the		byte extension: it is followed by an additional byte to represent the
	simple value. (To minimize confusion, only the values 32 to 255 are		simple value. (To minimize confusion, only the values 32 to 255 are
	used.) This maintains the structure of the initial bytes: as for the		used.) This maintains the structure of the initial bytes: as for the
	other major types, the length of these always depends on the		other major types, the length of these always depends on the
	additional information in the first byte. Table 2 lists the values		additional information in the first byte. Table 2 lists the values
	assigned and available for simple types.		assigned and available for simple types.
	skipping to change at page 16, line 25 ¶		skipping to change at page 16, line 25 ¶
	| | |		| | |
	| 23 | Undefined value |		| 23 | Undefined value |
	| | |		| | |
	| 24..31 | (Reserved) |		| 24..31 | (Reserved) |
	| | |		| | |
	| 32..255 | (Unassigned) |		| 32..255 | (Unassigned) |
	+---------+-----------------+		+---------+-----------------+
	Table 2: Simple Values		Table 2: Simple Values
	The 5-bit values of 25, 26, and 27 are for 16-bit, 32-bit, and 64-bit
	IEEE 754 binary floating-point values [IEEE.754.2008]. These
	floating-point values are encoded in the additional bytes of the
	appropriate size. (See Appendix D for some information about 16-bit
	floating point.)
	An encoder MUST NOT encode False as the two-byte sequence of 0xf814,		An encoder MUST NOT encode False as the two-byte sequence of 0xf814,
	MUST NOT encode True as the two-byte sequence of 0xf815, MUST NOT		MUST NOT encode True as the two-byte sequence of 0xf815, MUST NOT
	encode Null as the two-byte sequence of 0xf816, and MUST NOT encode		encode Null as the two-byte sequence of 0xf816, and MUST NOT encode
	Undefined value as the two-byte sequence of 0xf817. A decoder MUST		Undefined value as the two-byte sequence of 0xf817. A decoder MUST
	treat these two-byte sequences as an error. Similar prohibitions		treat these two-byte sequences as an error. Similar prohibitions
	apply to the unassigned simple values as well.		apply to the unassigned simple values as well.
			The 5-bit values of 25, 26, and 27 are for 16-bit, 32-bit, and 64-bit
			IEEE 754 binary floating-point values [IEEE.754.2008]. These
			floating-point values are encoded in the additional bytes of the
			appropriate size. (See Appendix D for some information about 16-bit
			floating point.)
	3.4. Optional Tagging of Items		3.4. Optional Tagging of Items
	In CBOR, a data item can optionally be preceded by a tag to give it		In CBOR, a data item can optionally be preceded by a tag to give it
	additional semantics while retaining its structure. The tag is major		additional semantics while retaining its structure. The tag is major
	type 6, and represents an integer number as indicated by the tag's		type 6, and represents an integer number as indicated by the tag's
	argument (Section 3); the (sole) data item is carried as content		argument (Section 3); the (sole) data item is carried as content
	data. If a tag requires structured data, this structure is encoded		data. If a tag requires structured data, this structure is encoded
	into the nested data item. The definition of a tag usually restricts		into the nested data item. The definition of a tag usually restricts
	what kinds of nested data item or items are valid.		what kinds of nested data item or items are valid.
	skipping to change at page 17, line 33 ¶		skipping to change at page 17, line 33 ¶
	value. The content of the tagged item is the data item (the value)		value. The content of the tagged item is the data item (the value)
	that is being tagged.		that is being tagged.
	IANA maintains a registry of tag values as described in Section 8.2.		IANA maintains a registry of tag values as described in Section 8.2.
	Table 3 provides a list of initial values, with definitions in the		Table 3 provides a list of initial values, with definitions in the
	rest of this section.		rest of this section.
	+-----------+--------------+----------------------------------------+		+-----------+--------------+----------------------------------------+
	| Tag | Data Item | Semantics |		| Tag | Data Item | Semantics |
	+-----------+--------------+----------------------------------------+		+-----------+--------------+----------------------------------------+
	| 0 | UTF-8 string | Standard date/time string; see Section |		| 0 | UTF-8 string | Standard date/time string; see |
	| | | 3.4.2 |		| | | Section 3.4.2 |
	| | | |		| | | |
	| 1 | multiple | Epoch-based date/time; see Section |		| 1 | multiple | Epoch-based date/time; see |
	| | | 3.4.3 |		| | | Section 3.4.3 |
	| | | |		| | | |
	| 2 | byte string | Positive bignum; see Section 3.4.4 |		| 2 | byte string | Positive bignum; see Section 3.4.4 |
	| | | |		| | | |
	| 3 | byte string | Negative bignum; see Section 3.4.4 |		| 3 | byte string | Negative bignum; see Section 3.4.4 |
	| | | |		| | | |
	| 4 | array | Decimal fraction; see Section 3.4.5 |		| 4 | array | Decimal fraction; see Section 3.4.5 |
	| | | |		| | | |
	| 5 | array | Bigfloat; see Section 3.4.5 |		| 5 | array | Bigfloat; see Section 3.4.5 |
	| | | |		| | | |
	| 6..20 | (Unassigned) | (Unassigned) |		| 6..20 | (Unassigned) | (Unassigned) |
	| | | |		| | | |
	| 21 | multiple | Expected conversion to base64url |		| 21 | multiple | Expected conversion to base64url |
	| | | encoding; see Section 3.4.6.2 |		| | | encoding; see Section 3.4.6.2 |
	| | | |		| | | |
	| 22 | multiple | Expected conversion to base64 |		| 22 | multiple | Expected conversion to base64 |
	| | | encoding; see Section 3.4.6.2 |		| | | encoding; see Section 3.4.6.2 |
	| | | |		| | | |
	| 23 | multiple | Expected conversion to base16 |		| 23 | multiple | Expected conversion to base16 |
	| | | encoding; see Section 3.4.6.2 |		| | | encoding; see Section 3.4.6.2 |
	| | | |		| | | |
	| 24 | byte string | Encoded CBOR data item; see Section |		| 24 | byte string | Encoded CBOR data item; see |
	| | | 3.4.6.1 |		| | | Section 3.4.6.1 |
	| | | |		| | | |
	| 25..31 | (Unassigned) | (Unassigned) |		| 25..31 | (Unassigned) | (Unassigned) |
	| | | |		| | | |
	| 32 | UTF-8 string | URI; see Section 3.4.6.3 |		| 32 | UTF-8 string | URI; see Section 3.4.6.3 |
	| | | |		| | | |
	| 33 | UTF-8 string | base64url; see Section 3.4.6.3 |		| 33 | UTF-8 string | base64url; see Section 3.4.6.3 |
	| | | |		| | | |
	| 34 | UTF-8 string | base64; see Section 3.4.6.3 |		| 34 | UTF-8 string | base64; see Section 3.4.6.3 |
	| | | |		| | | |
	| 35 | UTF-8 string | Regular expression; see Section |		| 35 | UTF-8 string | Regular expression; see |
	| | | 3.4.6.3 |		| | | Section 3.4.6.3 |
	| | | |		| | | |
	| 36 | UTF-8 string | MIME message; see Section 3.4.6.3 |		| 36 | UTF-8 string | MIME message; see Section 3.4.6.3 |
	| | | |		| | | |
	| 37..55798 | (Unassigned) | (Unassigned) |		| 37..55798 | (Unassigned) | (Unassigned) |
	| | | |		| | | |
	| 55799 | multiple | Self-describe CBOR; see Section 3.4.7 |		| 55799 | multiple | Self-described CBOR; see Section 3.4.7 |
	| | | |		| | | |
	| 55800+ | (Unassigned) | (Unassigned) |		| 55800+ | (Unassigned) | (Unassigned) |
	+-----------+--------------+----------------------------------------+		+-----------+--------------+----------------------------------------+
	Table 3: Values for Tags		Table 3: Values for Tags
	3.4.1. Date and Time		3.4.1. Date and Time
	Protocols using tag values 0 and 1 extend the generic data model		Protocols using tag values 0 and 1 extend the generic data model
	(Section 2) with data items representing points in time.		(Section 2) with data items representing points in time.
	skipping to change at page 19, line 22 ¶		skipping to change at page 19, line 22 ¶
	known as UNIX Epoch time. Note that leap seconds are handled		known as UNIX Epoch time. Note that leap seconds are handled
	specially by POSIX time and this results in a 1 second discontinuity		specially by POSIX time and this results in a 1 second discontinuity
	several times per decade.) Note that applications that require the		several times per decade.) Note that applications that require the
	expression of times beyond early 2106 cannot leave out support of		expression of times beyond early 2106 cannot leave out support of
	64-bit integers for the tagged value.		64-bit integers for the tagged value.
	Negative values (major type 1 and negative floating-point numbers)		Negative values (major type 1 and negative floating-point numbers)
	are interpreted as determined by the application requirements as		are interpreted as determined by the application requirements as
	there is no universal standard for UTC count-of-seconds time before		there is no universal standard for UTC count-of-seconds time before
	1970-01-01T00:00Z (this is particularly true for points in time that		1970-01-01T00:00Z (this is particularly true for points in time that
	precede discontinuities in national calendars).		precede discontinuities in national calendars). The same applies to
			non-finite values.
	To indicate fractional seconds, floating point values can be used		To indicate fractional seconds, floating point values can be used
	within Tag 1 instead of integer values. Note that this generally		within Tag 1 instead of integer values. Note that this generally
	requires binary64 support, as binary16 and binary32 provide non-zero		requires binary64 support, as binary16 and binary32 provide non-zero
	fractions of seconds only for a short period of time around early		fractions of seconds only for a short period of time around early
	1970. An application that requires Tag 1 support may restrict the		1970. An application that requires Tag 1 support may restrict the
	tagged value to be an integer (or a floating-point value) only.		tagged value to be an integer (or a floating-point value) only.
	3.4.4. Bignums		3.4.4. Bignums
	Protocols using tag values 2 and 3 extend the generic data model		Protocols using tag values 2 and 3 extend the generic data model
	(Section 2) with "bignums" representing arbitrary integers. In the		(Section 2) with "bignums" representing arbitrarily sized integers.
	generic data model, bignum values are not equal to integers from the		In the generic data model, bignum values are not equal to integers
	basic data model, but specific data models can define that		from the basic data model, but specific data models can define that
	equivalence.		equivalence, and preferred encoding never makes use of bignums that
			also can be expressed as basic integers (see below).
	Bignums are encoded as a byte string data item, which is interpreted		Bignums are encoded as a byte string data item, which is interpreted
	as an unsigned integer n in network byte order. For tag value 2, the		as an unsigned integer n in network byte order. For tag value 2, the
	value of the bignum is n. For tag value 3, the value of the bignum		value of the bignum is n. For tag value 3, the value of the bignum
	is -1 - n. Decoders that understand these tags MUST be able to		is -1 - n. The preferred encoding of the byte string is to leave out
	decode bignums that have leading zeroes.		any leading zeroes (note that this means the preferred encoding for
			n = 0 is the empty byte string, but see below). Decoders that
			understand these tags MUST be able to decode bignums that do have
			leading zeroes. The preferred encoding of an integer that can be
			represented using major type 0 or 1 is to encode it this way instead
			of as a bignum (which means that the empty string never occurs in a
			bignum when using preferred encoding). Note that this means the non-
			preferred choice of a bignum representation instead of a basic
			integer for encoding a number is not intended to have application
			semantics (just as the choice of a longer basic integer
			representation than needed, such as 0x1800 for 0x00 does not).
	For example, the number 18446744073709551616 (2**64) is represented		For example, the number 18446744073709551616 (2**64) is represented
	as 0b110_00010 (major type 6, tag 2), followed by 0b010_01001 (major		as 0b110_00010 (major type 6, tag 2), followed by 0b010_01001 (major
	type 2, length 9), followed by 0x010000000000000000 (one byte 0x01		type 2, length 9), followed by 0x010000000000000000 (one byte 0x01
	and eight bytes 0x00). In hexadecimal:		and eight bytes 0x00). In hexadecimal:
	C2 -- Tag 2		C2 -- Tag 2
	49 -- Byte string of length 9		49 -- Byte string of length 9
	010000000000000000 -- Bytes content		010000000000000000 -- Bytes content
	skipping to change at page 21, line 35 ¶		skipping to change at page 21, line 48 ¶
	3.4.6. Content Hints		3.4.6. Content Hints
	The tags in this section are for content hints that might be used by		The tags in this section are for content hints that might be used by
	generic CBOR processors. These content hints do not extend the		generic CBOR processors. These content hints do not extend the
	generic data model.		generic data model.
	3.4.6.1. Encoded CBOR Data Item		3.4.6.1. Encoded CBOR Data Item
	Sometimes it is beneficial to carry an embedded CBOR data item that		Sometimes it is beneficial to carry an embedded CBOR data item that
	is not meant to be decoded immediately at the time the enclosing data		is not meant to be decoded immediately at the time the enclosing data
	item is being parsed. Tag 24 (CBOR data item) can be used to tag the		item is being decoded. Tag 24 (CBOR data item) can be used to tag
	embedded byte string as a data item encoded in CBOR format.		the embedded byte string as a data item encoded in CBOR format.
	3.4.6.2. Expected Later Encoding for CBOR-to-JSON Converters		3.4.6.2. Expected Later Encoding for CBOR-to-JSON Converters
	Tags 21 to 23 indicate that a byte string might require a specific		Tags 21 to 23 indicate that a byte string might require a specific
	encoding when interoperating with a text-based representation. These		encoding when interoperating with a text-based representation. These
	tags are useful when an encoder knows that the byte string data it is		tags are useful when an encoder knows that the byte string data it is
	writing is likely to be later converted to a particular JSON-based		writing is likely to be later converted to a particular JSON-based
	usage. That usage specifies that some strings are encoded as base64,		usage. That usage specifies that some strings are encoded as base64,
	base64url, and so on. The encoder uses byte strings instead of doing		base64url, and so on. The encoder uses byte strings instead of doing
	the encoding itself to reduce the message size, to reduce the code		the encoding itself to reduce the message size, to reduce the code
	size of the encoder, or both. The encoder does not know whether or		size of the encoder, or both. The encoder does not know whether or
	not the converter will be generic, and therefore wants to say what it		not the converter will be generic, and therefore wants to say what it
	believes is the proper way to convert binary strings to JSON.		believes is the proper way to convert binary strings to JSON.
	The data item tagged can be a byte string or any other data item. In		The data item tagged can be a byte string or any other data item. In
	the latter case, the tag applies to all of the byte string data items		the latter case, the tag applies to all of the byte string data items
	contained in the data item, except for those contained in a nested		contained in the data item, except for those contained in a nested
	data item tagged with an expected conversion.		data item tagged with an expected conversion.
	These three tag types suggest conversions to three of the base data		These three tag types suggest conversions to three of the base data
	encodings defined in [RFC4648]. For base64url encoding, padding is		encodings defined in [RFC4648]. For base64url encoding (tag 21),
	not used (see Section 3.2 of RFC 4648); that is, all trailing equals		padding is not used (see Section 3.2 of RFC 4648); that is, all
	signs ("=") are removed from the base64url-encoded string. Later		trailing equals signs ("=") are removed from the encoded string. For
	tags might be defined for other data encodings of RFC 4648 or for		base64 encoding (tag 22), padding is used as defined in RFC 4648.
	other ways to encode binary data in strings.		For both base64url and base64, padding bits are set to zero (see
			Section 3.5 of RFC 4648), and encoding is performed without the
			inclusion of any line breaks, whitespace, or other additional
			characters. Note that, for all three tags, the encoding of the empty
			byte string is the empty text string.
	3.4.6.3. Encoded Text		3.4.6.3. Encoded Text
	Some text strings hold data that have formats widely used on the		Some text strings hold data that have formats widely used on the
	Internet, and sometimes those formats can be validated and presented		Internet, and sometimes those formats can be validated and presented
	to the application in appropriate form by the decoder. There are		to the application in appropriate form by the decoder. There are
	tags for some of these formats.		tags for some of these formats.
	o Tag 32 is for URIs, as defined in [RFC3986];		o Tag 32 is for URIs, as defined in [RFC3986];
	skipping to change at page 22, line 44 ¶		skipping to change at page 23, line 12 ¶
	expression, or more than just the text of the regular expression		expression, or more than just the text of the regular expression
	itself, need to be conveyed.)		itself, need to be conveyed.)
	o Tag 36 is for MIME messages (including all headers), as defined in		o Tag 36 is for MIME messages (including all headers), as defined in
	[RFC2045];		[RFC2045];
	Note that tags 33 and 34 differ from 21 and 22 in that the data is		Note that tags 33 and 34 differ from 21 and 22 in that the data is
	transported in base-encoded form for the former and in raw byte		transported in base-encoded form for the former and in raw byte
	string form for the latter.		string form for the latter.
	3.4.7. Self-Describe CBOR		3.4.7. Self-Described CBOR
	In many applications, it will be clear from the context that CBOR is		In many applications, it will be clear from the context that CBOR is
	being employed for encoding a data item. For instance, a specific		being employed for encoding a data item. For instance, a specific
	protocol might specify the use of CBOR, or a media type is indicated		protocol might specify the use of CBOR, or a media type is indicated
	that specifies its use. However, there may be applications where		that specifies its use. However, there may be applications where
	such context information is not available, such as when CBOR data is		such context information is not available, such as when CBOR data is
	stored in a file and disambiguating metadata is not in use. Here, it		stored in a file and disambiguating metadata is not in use. Here, it
	may help to have some distinguishing characteristics for the data		may help to have some distinguishing characteristics for the data
	itself.		itself.
	Tag 55799 is defined for this purpose. It does not impart any		Tag 55799 is defined for this purpose. It does not impart any
	special semantics on the data item that follows; that is, the		special semantics on the data item that follows; that is, the
	semantics of a data item tagged with tag 55799 is exactly identical		semantics of a data item tagged with tag 55799 is exactly identical
	to the semantics of the data item itself.		to the semantics of the data item itself.
	The serialization of this tag is 0xd9d9f7, which appears not to be in		The serialization of this tag is 0xd9d9f7, which appears not to be in
	use as a distinguishing mark for frequently used file types. In		use as a distinguishing mark for frequently used file types. In
	particular, it is not a valid start of a Unicode text in any Unicode		particular, it is not a valid start of a Unicode text in any Unicode
	encoding if followed by a valid CBOR data item.		encoding if followed by a valid CBOR data item.
	For instance, a decoder might be able to parse both CBOR and JSON.		For instance, a decoder might be able to decode both CBOR and JSON.
	Such a decoder would need to mechanically distinguish the two		Such a decoder would need to mechanically distinguish the two
	formats. An easy way for an encoder to help the decoder would be to		formats. An easy way for an encoder to help the decoder would be to
	tag the entire CBOR item with tag 55799, the serialization of which		tag the entire CBOR item with tag 55799, the serialization of which
	will never be found at the beginning of a JSON text.		will never be found at the beginning of a JSON text.
	4. Creating CBOR-Based Protocols		4. Creating CBOR-Based Protocols
	Data formats such as CBOR are often used in environments where there		Data formats such as CBOR are often used in environments where there
	is no format negotiation. A specific design goal of CBOR is to not		is no format negotiation. A specific design goal of CBOR is to not
	need any included or assumed schema: a decoder can take a CBOR item		need any included or assumed schema: a decoder can take a CBOR item
	skipping to change at page 25, line 22 ¶		skipping to change at page 25, line 34 ¶
	generally can choose to completely fail the decoding (issue an error		generally can choose to completely fail the decoding (issue an error
	and/or stop processing altogether), substitute the problematic data		and/or stop processing altogether), substitute the problematic data
	and data items using a decoder-specific convention that clearly		and data items using a decoder-specific convention that clearly
	indicates there has been a problem, or take some other action.		indicates there has been a problem, or take some other action.
	4.3.1. Incomplete CBOR Data Items		4.3.1. Incomplete CBOR Data Items
	The representation of a CBOR data item has a specific length,		The representation of a CBOR data item has a specific length,
	determined by its initial bytes and by the structure of any data		determined by its initial bytes and by the structure of any data
	items enclosed in the data items. If less data is available, this		items enclosed in the data items. If less data is available, this
	can be treated as a syntax error. A decoder may also implement		can be treated as a syntax error. A decoder may also decode
	incremental parsing, that is, decode the data item as far as it is		incrementally, that is, decode the data item as far as it is
	available and present the data found so far (such as in an event-		available and present the data found so far (such as in an event-
	based interface), with the option of continuing the decoding once		based interface), with the option of continuing the decoding once
	further data is available.		further data is available.
	Examples of incomplete data items include:		Examples of incomplete data items include:
	o A decoder expects a certain number of array or map entries but		o A decoder expects a certain number of array or map entries but
	instead encounters the end of the data.		instead encounters the end of the data.
	o A decoder processes what it expects to be the last pair in a map		o A decoder processes what it expects to be the last pair in a map
	skipping to change at page 26, line 16 ¶		skipping to change at page 26, line 31 ¶
	where there is no immediately enclosing (unclosed) indefinite-length		where there is no immediately enclosing (unclosed) indefinite-length
	item.		item.
	4.3.3. Unknown Additional Information Values		4.3.3. Unknown Additional Information Values
	At the time of writing, some additional information values are		At the time of writing, some additional information values are
	unassigned and reserved for future versions of this document (see		unassigned and reserved for future versions of this document (see
	Section 6.2). Since the overall syntax for these additional		Section 6.2). Since the overall syntax for these additional
	information values is not yet defined, a decoder that sees an		information values is not yet defined, a decoder that sees an
	additional information value that it does not understand cannot		additional information value that it does not understand cannot
	continue parsing.		continue decoding.
	4.4. Other Decoding Errors		4.4. Other Decoding Errors
	A CBOR data item may be syntactically well-formed but present a		A CBOR data item may be syntactically well-formed but present a
	problem with interpreting the data encoded in it in the CBOR data		problem with interpreting the data encoded in it in the CBOR data
	model. Generally speaking, a decoder that finds a data item with		model. Generally speaking, a decoder that finds a data item with
	such a problem might issue a warning, might stop processing		such a problem might issue a warning, might stop processing
	altogether, might handle the error and make the problematic value		altogether, might handle the error and make the problematic value
	available to the application as such, or take some other type of		available to the application as such, or take some other type of
	action.		action.
	skipping to change at page 31, line 13 ¶		skipping to change at page 31, line 30 ¶
	by definition variation-tolerant; the distinction is only relevant if		by definition variation-tolerant; the distinction is only relevant if
	a constrained implementation of a CBOR decoder meets a variant		a constrained implementation of a CBOR decoder meets a variant
	encoder.		encoder.
	The preferred serialization always uses the shortest form of		The preferred serialization always uses the shortest form of
	representing the argument (Section 3)); it also uses the shortest		representing the argument (Section 3)); it also uses the shortest
	floating point encoding that preserves the value being encoded (see		floating point encoding that preserves the value being encoded (see
	Section 4.6). Definite length encoding is preferred whenever the		Section 4.6). Definite length encoding is preferred whenever the
	length is known at the time the serialization of the item starts.		length is known at the time the serialization of the item starts.
	4.10. Canonical CBOR		4.10. Canonically Encoded CBOR
	Some protocols may want encoders to only emit CBOR in a particular		Some protocols may want encoders to only emit CBOR in a particular
	canonical format; those protocols might also have the decoders check		canonical format; those protocols might also have the decoders check
	that their input is canonical. Those protocols are free to define		that their input is canonical. Those protocols are free to define
	what they mean by a canonical format and what encoders and decoders		what they mean by a canonical format and what encoders and decoders
	are expected to do. This section defines a set of restrictions that		are expected to do. This section defines a set of restrictions that
	can serve as the base of such a canonical format.		can serve as the base of such a canonical format.
	A CBOR encoding satisfies the "core canonicalization requirements" if		A CBOR encoding satisfies the "core canonicalization requirements" if
	it satisfies the following restrictions:		it satisfies the following restrictions:
	skipping to change at page 34, line 13 ¶		skipping to change at page 34, line 30 ¶
	4. 100, encoded as 0x1864.		4. 100, encoded as 0x1864.
	5. "z", encoded as 0x617a.		5. "z", encoded as 0x617a.
	6. [-1], encoded as 0x8120.		6. [-1], encoded as 0x8120.
	7. "aa", encoded as 0x626161.		7. "aa", encoded as 0x626161.
	8. [100], encoded as 0x811864.		8. [100], encoded as 0x811864.
	4.11. Strict Mode		4.11. Strict Decoding Mode
	Some areas of application of CBOR do not require canonicalization		Some areas of application of CBOR do not require canonicalization
	(Section 4.10) but may require that different decoders reach the same		(Section 4.10) but may require that different decoders reach the same
	(semantically equivalent) results, even in the presence of		(semantically equivalent) results, even in the presence of
	potentially malicious data. This can be required if one application		potentially malicious data. This can be required if one application
	(such as a firewall or other protecting entity) makes a decision		(such as a firewall or other protecting entity) makes a decision
	based on the data that another application, which independently		based on the data that another application, which independently
	decodes the data, relies on.		decodes the data, relies on.
	Normally, it is the responsibility of the sender to avoid ambiguously		Normally, it is the responsibility of the sender to avoid ambiguously
	skipping to change at page 39, line 4 ¶		skipping to change at page 39, line 24 ¶
	part of the codepoint space has been allocated, and the space is		part of the codepoint space has been allocated, and the space is
	abundant (although the early numbers are more efficient than the		abundant (although the early numbers are more efficient than the
	later ones). Implementations receiving an unknown tag can choose		later ones). Implementations receiving an unknown tag can choose
	to simply ignore it or to process it as an unknown tag wrapping		to simply ignore it or to process it as an unknown tag wrapping
	the following data item. The IANA registry in Section 8.2 is the		the following data item. The IANA registry in Section 8.2 is the
	appropriate way to address the extensibility of this codepoint		appropriate way to address the extensibility of this codepoint
	space.		space.
	o the "additional information" space. An implementation receiving		o the "additional information" space. An implementation receiving
	an unknown additional information value has no way to continue		an unknown additional information value has no way to continue
	parsing, so allocating codepoints to this space is a major step.		decoding, so allocating codepoints to this space is a major step.
	There are also very few codepoints left.		There are also very few codepoints left.
	6.2. Curating the Additional Information Space		6.2. Curating the Additional Information Space
	The human mind is sometimes drawn to filling in little perceived gaps		The human mind is sometimes drawn to filling in little perceived gaps
	to make something neat. We expect the remaining gaps in the		to make something neat. We expect the remaining gaps in the
	codepoint space for the additional information values to be an		codepoint space for the additional information values to be an
	attractor for new ideas, just because they are there.		attractor for new ideas, just because they are there.
	The present specification does not manage the additional information		The present specification does not manage the additional information
	skipping to change at page 44, line 22 ¶		skipping to change at page 44, line 49 ¶
	vulnerabilities by reducing parser complexity, by giving the entire		vulnerabilities by reducing parser complexity, by giving the entire
	range of encodable values a meaning where possible.		range of encodable values a meaning where possible.
	Resource exhaustion attacks might attempt to lure a decoder into		Resource exhaustion attacks might attempt to lure a decoder into
	allocating very big data items (strings, arrays, maps) or exhaust the		allocating very big data items (strings, arrays, maps) or exhaust the
	stack depth by setting up deeply nested items. Decoders need to have		stack depth by setting up deeply nested items. Decoders need to have
	appropriate resource management to mitigate these attacks. (Items		appropriate resource management to mitigate these attacks. (Items
	for which very large sizes are given can also attempt to exploit		for which very large sizes are given can also attempt to exploit
	integer overflow vulnerabilities.)		integer overflow vulnerabilities.)
	Applications where a CBOR data item is examined by a gatekeeper		Protocols that are used in a security context should be defined in
	function and later used by a different application may exhibit		such a way that potential multiple interpretations are reliably
	vulnerabilities when multiple interpretations of the data item are		reduced to a single one. For example, an attacker could make use of
	possible. For example, an attacker could make use of duplicate keys		duplicate keys in maps or precision issues in numbers to make one
	in maps and precision issues in numbers to make the gatekeeper base		decoder base its decisions on a different interpretation than the one
	its decisions on a different interpretation than the one that will be		that will be used by a second decoder. To facilitate this, encoder
	used by the second application. Protocols that are used in a		and decoder implementations used in such contexts should provide at
	security context should be defined in such a way that these multiple		least one strict mode of operation (Section 4.11).
	interpretations are reliably reduced to a single one. To facilitate
	this, encoder and decoder implementations used in such contexts
	should provide at least one strict mode of operation (Section 4.11).
	10. Acknowledgements		10. Acknowledgements
	CBOR was inspired by MessagePack. MessagePack was developed and		CBOR was inspired by MessagePack. MessagePack was developed and
	promoted by Sadayuki Furuhashi ("frsyuki"). This reference to		promoted by Sadayuki Furuhashi ("frsyuki"). This reference to
	MessagePack is solely for attribution; CBOR is not intended as a		MessagePack is solely for attribution; CBOR is not intended as a
	version of or replacement for MessagePack, as it has different design		version of or replacement for MessagePack, as it has different design
	goals and requirements.		goals and requirements.
	The need for functionality beyond the original MessagePack		The need for functionality beyond the original MessagePack
	skipping to change at page 54, line 15 ¶		skipping to change at page 54, line 15 ¶
	| | |		| | |
	| 0xba | map (four-byte uint32_t for n, and then n pairs of |		| 0xba | map (four-byte uint32_t for n, and then n pairs of |
	| | data items follow) |		| | data items follow) |
	| | |		| | |
	| 0xbb | map (eight-byte uint64_t for n, and then n pairs of |		| 0xbb | map (eight-byte uint64_t for n, and then n pairs of |
	| | data items follow) |		| | data items follow) |
	| | |		| | |
	| 0xbf | map, pairs of data items follow, terminated by |		| 0xbf | map, pairs of data items follow, terminated by |
	| | "break" |		| | "break" |
	| | |		| | |
	| 0xc0 | Text-based date/time (data item follows; see Section |		| 0xc0 | Text-based date/time (data item follows; see |
	| | 3.4.2) |		| | Section 3.4.2) |
	| | |		| | |
	| 0xc1 | Epoch-based date/time (data item follows; see |		| 0xc1 | Epoch-based date/time (data item follows; see |
	| | Section 3.4.3) |		| | Section 3.4.3) |
	| | |		| | |
	| 0xc2 | Positive bignum (data item "byte string" follows) |		| 0xc2 | Positive bignum (data item "byte string" follows) |
	| | |		| | |
	| 0xc3 | Negative bignum (data item "byte string" follows) |		| 0xc3 | Negative bignum (data item "byte string" follows) |
	| | |		| | |
	| 0xc4 | Decimal Fraction (data item "array" follows; see |		| 0xc4 | Decimal Fraction (data item "array" follows; see |
	| | Section 3.4.5) |		| | Section 3.4.5) |
	| | |		| | |
	| 0xc5 | Bigfloat (data item "array" follows; see Section |		| 0xc5 | Bigfloat (data item "array" follows; see |
	| | 3.4.5) |		| | Section 3.4.5) |
	| | |		| | |
	| 0xc6..0xd4 | (tagged item) |		| 0xc6..0xd4 | (tagged item) |
	| | |		| | |
	| 0xd5..0xd7 | Expected Conversion (data item follows; see Section |		| 0xd5..0xd7 | Expected Conversion (data item follows; see |
	| | 3.4.6.2) |		| | Section 3.4.6.2) |
	| | |		| | |
	| 0xd8..0xdb | (more tagged items, 1/2/4/8 bytes and then a data |		| 0xd8..0xdb | (more tagged items, 1/2/4/8 bytes and then a data |
	| | item follow) |		| | item follow) |
	| | |		| | |
	| 0xe0..0xf3 | (simple value) |		| 0xe0..0xf3 | (simple value) |
	| | |		| | |
	| 0xf4 | False |		| 0xf4 | False |
	| | |		| | |
	| 0xf5 | True |		| 0xf5 | True |
	| | |		| | |
	skipping to change at page 56, line 51 ¶		skipping to change at page 56, line 51 ¶
	return -1; // signal break out		return -1; // signal break out
	else fail(); // no enclosing indefinite		else fail(); // no enclosing indefinite
	default: fail(); // wrong mt		default: fail(); // wrong mt
	}		}
	return 0; // no break out		return 0; // no break out
	}		}
	Figure 1: Pseudocode for Well-Formedness Check		Figure 1: Pseudocode for Well-Formedness Check
	Note that the remaining complexity of a complete CBOR decoder is		Note that the remaining complexity of a complete CBOR decoder is
	about presenting data that has been parsed to the application in an		about presenting data that has been decoded to the application in an
	appropriate form.		appropriate form.
	Major types 0 and 1 are designed in such a way that they can be		Major types 0 and 1 are designed in such a way that they can be
	encoded in C from a signed integer without actually doing an if-then-		encoded in C from a signed integer without actually doing an if-then-
	else for positive/negative (Figure 2). This uses the fact that		else for positive/negative (Figure 2). This uses the fact that
	(-1-n), the transformation for major type 1, is the same as ~n		(-1-n), the transformation for major type 1, is the same as ~n
	(bitwise complement) in C unsigned arithmetic; ~n can then be		(bitwise complement) in C unsigned arithmetic; ~n can then be
	expressed as (-1)^n for the negative case, while 0^n leaves n		expressed as (-1)^n for the negative case, while 0^n leaves n
	unchanged for non-negative. The sign of a number can be converted to		unchanged for non-negative. The sign of a number can be converted to
	-1 for negative and 0 for non-negative (0 or positive) by arithmetic-		-1 for negative and 0 for non-negative (0 or positive) by arithmetic-
	skipping to change at page 61, line 32 ¶		skipping to change at page 61, line 32 ¶
	+-------------+--------------------------+--------------------------+		+-------------+--------------------------+--------------------------+
	Table 6: Examples for Different Levels of Conciseness		Table 6: Examples for Different Levels of Conciseness
	Appendix F. Changes from RFC 7049		Appendix F. Changes from RFC 7049
	The following is a list of known changes from RFC 7049. This list is		The following is a list of known changes from RFC 7049. This list is
	non-authoritative. It is meant to help reviewers see the significant		non-authoritative. It is meant to help reviewers see the significant
	differences.		differences.
	o Updated reference for [RFC4267] to [RFC8259] in many places		o Updated reference for [RFC4627] to [RFC8259] in many places
	o Updated reference for [CNN-TERMS] to [RFC7228]		o Updated reference for [CNN-TERMS] to [RFC7228]
	o Added a comment to the last example in Section 2.2.1 (added		o Added a comment to the last example in Section 2.2.1 (added
	"Second value")		"Second value")
	o Fixed a bug in the example in Section 2.4.2 ("29" -> "49")		o Fixed a bug in the example in Section 2.4.2 ("29" -> "49")
	o Fixed a bug in the last paragraph of Section 3.6 ("0b000_11101" ->		o Fixed a bug in the last paragraph of Section 3.6 ("0b000_11101" ->
	"0b000_11001")		"0b000_11001")
End of changes. 55 change blocks.
	145 lines changed or deleted		153 lines changed or added
This html diff was produced by rfcdiff 1.47. The latest version is available from http://tools.ietf.org/tools/rfcdiff/