draft-ietf-cose-hpke-00.txt		draft-ietf-cose-hpke-01.txt
	COSE H. Tschofenig		COSE H. Tschofenig
	Internet-Draft Arm Limited		Internet-Draft Arm Limited
	Intended status: Standards Track R. Housley		Intended status: Standards Track R. Housley
	Expires: 14 July 2022 Vigil Security		Expires: 8 September 2022 Vigil Security
	B. Moran		B. Moran
	Arm Limited		Arm Limited
	10 January 2022		7 March 2022
	Use of Hybrid Public-Key Encryption (HPKE) with CBOR Object Signing and		Use of Hybrid Public-Key Encryption (HPKE) with CBOR Object Signing and
	Encryption (COSE)		Encryption (COSE)
	draft-ietf-cose-hpke-00		draft-ietf-cose-hpke-01
	Abstract		Abstract
	This specification defines hybrid public-key encryption (HPKE) for		This specification defines hybrid public-key encryption (HPKE) for
	use with CBOR Object Signing and Encryption (COSE).		use with CBOR Object Signing and Encryption (COSE). HPKE offers a
			variant of public-key encryption of arbitrary-sized plaintexts for a
			recipient public key.
			HPKE works for any combination of an asymmetric key encapsulation
			mechanism (KEM), key derivation function (KDF), and authenticated
			encryption with additional data (AEAD) encryption function.
			Authentication for HPKE in COSE is provided by COSE-native security
			mechanisms.
	Status of This Memo		Status of This Memo
	This Internet-Draft is submitted in full conformance with the		This Internet-Draft is submitted in full conformance with the
	provisions of BCP 78 and BCP 79.		provisions of BCP 78 and BCP 79.
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	Copyright Notice		Copyright Notice
	Copyright (c) 2022 IETF Trust and the persons identified as the		Copyright (c) 2022 IETF Trust and the persons identified as the
	document authors. All rights reserved.		document authors. All rights reserved.
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	Please review these documents carefully, as they describe your rights		Please review these documents carefully, as they describe your rights
	skipping to change at page 2, line 19 ¶		skipping to change at page 2, line 28 ¶
	modifications of such material outside the IETF Standards Process.		modifications of such material outside the IETF Standards Process.
	Without obtaining an adequate license from the person(s) controlling		Without obtaining an adequate license from the person(s) controlling
	the copyright in such materials, this document may not be modified		the copyright in such materials, this document may not be modified
	outside the IETF Standards Process, and derivative works of it may		outside the IETF Standards Process, and derivative works of it may
	not be created outside the IETF Standards Process, except to format		not be created outside the IETF Standards Process, except to format
	it for publication as an RFC or to translate it into languages other		it for publication as an RFC or to translate it into languages other
	than English.		than English.
	Table of Contents		Table of Contents
	1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2		1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
	2. Conventions and Terminology . . . . . . . . . . . . . . . . . 3		2. Conventions and Terminology . . . . . . . . . . . . . . . . . 3
	3. HPKE for COSE . . . . . . . . . . . . . . . . . . . . . . . . 3		3. HPKE for COSE . . . . . . . . . . . . . . . . . . . . . . . . 3
	3.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . 3		3.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . 3
	3.2. HPKE Encryption with SealBase . . . . . . . . . . . . . . 4		3.2. HPKE Encryption with SealBase . . . . . . . . . . . . . . 4
	3.3. HPKE Decryption with Open . . . . . . . . . . . . . . . . 5		3.3. HPKE Decryption with OpenBase . . . . . . . . . . . . . . 5
	3.4. Info Structure . . . . . . . . . . . . . . . . . . . . . 5		3.4. Info Structure . . . . . . . . . . . . . . . . . . . . . 5
	4. Example . . . . . . . . . . . . . . . . . . . . . . . . . . . 6		4. Example . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
	5. Security Considerations . . . . . . . . . . . . . . . . . . . 7		5. Security Considerations . . . . . . . . . . . . . . . . . . . 7
	6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8		6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
	7. References . . . . . . . . . . . . . . . . . . . . . . . . . 9		6.1. HPKE/P-256+HKDF-256 and AES-128-GCM . . . . . . . . . . . 8
			6.2. HPKE/P-512+HKDF-512 and AES-256-GCM . . . . . . . . . . . 8
			7. References . . . . . . . . . . . . . . . . . . . . . . . . . 8
	7.1. Normative References . . . . . . . . . . . . . . . . . . 9		7.1. Normative References . . . . . . . . . . . . . . . . . . 9
	7.2. Informative References . . . . . . . . . . . . . . . . . 9		7.2. Informative References . . . . . . . . . . . . . . . . . 9
	Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 9		Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 9
	Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9		Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9
	1. Introduction		1. Introduction
	Hybrid public-key encryption (HPKE) [I-D.irtf-cfrg-hpke] is a scheme		Hybrid public-key encryption (HPKE) [I-D.irtf-cfrg-hpke] is a scheme
	that provides public key encryption of arbitrary-sized plaintexts		that provides public key encryption of arbitrary-sized plaintexts
	given a recipient's public key. HPKE utilizes a non-interactive		given a recipient's public key. HPKE utilizes a non-interactive
	ephemeral-static Diffie-Hellman exchange to establish a shared		ephemeral-static Diffie-Hellman exchange to establish a shared
	secret, which is then used to encrypt plaintext.		secret. The motivation for standardizing a public key encryption
			scheme is explained in the introduction of [I-D.irtf-cfrg-hpke].
	The HPKE specification defines several features for use with public		The HPKE specification defines several features for use with public
	key encryption and a subset of those features is applied to COSE		key encryption and a subset of those features is applied to COSE
	[RFC8152]. Since COSE provides constructs for authenticcation, those		[RFC8152]. Since COSE provides constructs for authentication, those
	are not re-used from the HPKE specification. This specification uses		are not re-used from the HPKE specification. This specification uses
	the "base" mode (as it is called in HPKE specification language).		the "base" mode, as it is called in HPKE specification language.
	2. Conventions and Terminology		2. Conventions and Terminology
	The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",		The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
	"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and		"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
	"OPTIONAL" in this document are to be interpreted as described in		"OPTIONAL" in this document are to be interpreted as described in
	BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all		BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
	capitals, as shown here.		capitals, as shown here.
	This specification uses the following abbreviations and terms: -		This specification uses the following abbreviations and terms: -
	Content-encryption key (CEK), a term defined in RFC 2630 [RFC2630]. -		Content-encryption key (CEK), a term defined in CMS [RFC2630]. -
	Hybrid Public Key Encryption (HPKE) is defined in		Hybrid Public Key Encryption (HPKE) is defined in
	[I-D.irtf-cfrg-hpke]. - pkR is the public key of the recipient, as		[I-D.irtf-cfrg-hpke]. - pkR is the public key of the recipient, as
	defined in [I-D.irtf-cfrg-hpke]. - skR is the private key of the		defined in [I-D.irtf-cfrg-hpke]. - skR is the private key of the
	recipient, as defined in [I-D.irtf-cfrg-hpke].		recipient, as defined in [I-D.irtf-cfrg-hpke].
	3. HPKE for COSE		3. HPKE for COSE
	3.1. Overview		3.1. Overview
	The CDDL for the COSE_Encrypt structure, as used with this		The CDDL for the COSE_Encrypt structure, as used with this
	specification, is shown in Figure 1. The structures referenced below		specification, is shown in Figure 1.
	are found in the CDDL.
	HPKE, when used with COSE, follows a three layer structure:		HPKE, when used with COSE, follows a two layer structure:
	* Layer 0 (corresponding to the COSE_Encrypt structure) contains		* Layer 0 (corresponding to the COSE_Encrypt structure) contains
	content encrypted with the CEK. This ciphertext may be detached.		content (plaintext) encrypted with the CEK. This ciphertext may
	If not detached, then it is included in the COSE_Encrypt		be detached. If not detached, then it is included in the
	structure.		COSE_Encrypt structure.
	* Layer 1 (see COSE_recipient_outer structure) includes the
	encrypted CEK.
	* Layer 2 (in the COSE_recipient_inner structure) contains		* Layer 1 (corresponding to a recipient structure) contains
	parameters needed for HPKE to generate a shared secret used to		parameters needed for HPKE to generate a shared secret used to
	encrypt the CEK from layer 1.		encrypt the CEK. This layer includes the encrypted CEK.
			This two-layer structure is used to encrypt content that can also be
			shared with multiple parties at the expense of a single additional
			encryption operation. As stated above, the specification uses a CEK
			to encrypt the content at layer 0.
			For example, the content encrypted at layer 0 is a firmware image.
			The same ciphertext firmware image is processed by all of the
			recipients; however, each recipient uses their own private key to
			obtain the CEK.
	COSE_Encrypt_Tagged = #6.96(COSE_Encrypt)		COSE_Encrypt_Tagged = #6.96(COSE_Encrypt)
	SUIT_Encryption_Info = COSE_Encrypt_Tagged		HPKE_Encryption_Info = COSE_Encrypt_Tagged
	; Layer 0		; Layer 0
	COSE_Encrypt = [		COSE_Encrypt = [
	Headers,		Headers,
	ciphertext : bstr / nil,		ciphertext : bstr / nil,
	recipients : [+COSE_recipient_outer]		recipients : + COSE_recipient
	]		]
	; Layer 1		; Layer 1
	COSE_recipient_outer = [		COSE_recipient = [
	protected : bstr .size 0,		protected : bstr .cbor header_map, ; must contain alg parameter
	unprotected : header_map, ; must contain alg
	encCEK : bstr, ; CEK encrypted with HPKE-derived shared secret
	recipients : [ + COSE_recipient_inner ]
	]
	; Layer 2
	COSE_recipient_inner = [
	protected : bstr .cbor header_map, ; must contain HPKE alg
	unprotected : header_map, ; must contain kid and ephemeral public key		unprotected : header_map, ; must contain kid and ephemeral public key
	empty : null,		encCEK : bstr, ; CEK encrypted with HPKE-derived shared secret
	empty : null
	]		]
	header_map = {		header_map = {
	Generic_Headers,		Generic_Headers,
	* label =values,		* label =values,
	}		}
	Figure 1: CDDL for HPKE-based COSE_Encrypt Structure		Figure 1: CDDL for HPKE-based COSE_Encrypt Structure
	The COSE_recipient_outer structure shown in Figure 1 includes the		The COSE_recipient structure shown in Figure 1 is repeated for each
	encrypted CEK (in the encCEK structure) and the COSE_recipient_inner		recipient, and it includes the encrypted CEK as well as the sender-
	structure, also shown in Figure 1, contains the ephemeral public key		generated ephemeral public key in the unprotected header structure.
	(in the unprotected structure).
	3.2. HPKE Encryption with SealBase		3.2. HPKE Encryption with SealBase
	The SealBase(pkR, info, aad, pt) function is used to encrypt a		The SealBase(pkR, info, aad, pt) function is used to encrypt a
	plaintext pt to a recipient's public key (pkR). For use in this		plaintext pt to a recipient's public key (pkR).
	specification, the plaintext "pt" passed into the SealBase is the
	CEK. The CEK is a random byte sequence of length appropriate for the		IMPORTANT: For use in this specification, the plaintext "pt" passed
	encryption algorithm selected in layer 0. For example, AES-128-GCM		into the SealBase is the CEK. The CEK is a random byte sequence of
	requires a 16 byte key and the CEK would therefore be 16 bytes long.		length appropriate for the encryption algorithm selected in layer 0.
			For example, AES-128-GCM requires a 16 byte key and the CEK would
			therefore be 16 bytes long.
	The "info" parameter can be used to influence the generation of keys		The "info" parameter can be used to influence the generation of keys
	and the "aad" parameter provides additional authenticated data to the		and the "aad" parameter provides additional authenticated data to the
	AEAD algorithm in use. If successful, SealBase() will output a		AEAD algorithm in use. This specification does not mandate the use
	ciphertext "ct" and an encapsulated key "enc". The content of enc is		of the info and the aad parameters.
	the ephemeral public key.
			If SealBase() is successful, it will output a ciphertext "ct" and an
			encapsulated key "enc". The content of enc is the ephemeral public
			key.
	The content of the info parameter is based on the 'COSE_KDF_Context'		The content of the info parameter is based on the 'COSE_KDF_Context'
	structure, which is detailed in Figure 2.		structure, which is detailed in Figure 2.
	3.3. HPKE Decryption with Open		3.3. HPKE Decryption with OpenBase
	The recipient will use the OpenBase(enc, skR, info, aad, ct) function		The recipient will use the OpenBase(enc, skR, info, aad, ct) function
	with the enc and ct parameters received from the sender. The "aad"		with the enc and ct parameters received from the sender. The "aad"
	and the "info" parameters are obtained via the context of the usage.		and the "info" parameters are obtained via the context of the usage.
	The OpenBase function will, if successful, decrypt "ct". When		The OpenBase function will, if successful, decrypt "ct". When
	decrypted, the result will be the CEK. The CK is the symmetric key		decrypted, the result will be the CEK. The CK is the symmetric key
	used to decrypt the ciphertext in the COSE_Encrypt structure.		used to decrypt the ciphertext in layer 0 of the COSE_Encrypt
			structure.
	3.4. Info Structure		3.4. Info Structure
			This section provides a suggestion for constructing the info
			structure, when used with SealBase() and OpenBase(). Note that the
			use of the aad and the info structures for these two functions is
			optional. Profiles of this specification may require their use and
			may define different info structure.
	This specification re-uses the context information structure defined		This specification re-uses the context information structure defined
	in [RFC8152] for use with the HPKE algorithm. This payload becomes		in [RFC8152] as a foundation for the info structure. This payload
	the content of the info parameter for the HPKE functions. For better		becomes the content of the info parameter for the HPKE functions,
	readability of this specification the COSE_KDF_Context structure is		when utilized. For better readability of this specification the
	repeated in Figure 2.		COSE_KDF_Context structure is repeated in Figure 2.
	PartyInfo = (		PartyInfo = (
	identity : bstr / nil,		identity : bstr / nil,
	nonce : bstr / int / nil,		nonce : bstr / int / nil,
	other : bstr / nil		other : bstr / nil
	)		)
	COSE_KDF_Context = [		COSE_KDF_Context = [
	AlgorithmID : int / tstr,		AlgorithmID : int / tstr,
	PartyUInfo : [ PartyInfo ],		PartyUInfo : [ PartyInfo ],
	skipping to change at page 6, line 5 ¶		skipping to change at page 6, line 25 ¶
	SuppPubInfo : [		SuppPubInfo : [
	keyDataLength : uint,		keyDataLength : uint,
	protected : empty_or_serialized_map,		protected : empty_or_serialized_map,
	? other : bstr		? other : bstr
	],		],
	? SuppPrivInfo : bstr		? SuppPrivInfo : bstr
	]		]
	Figure 2: COSE_KDF_Context Data Structure for info parameter		Figure 2: COSE_KDF_Context Data Structure for info parameter
	Since this specification may be used in a number of different		The fields in Figure 2 are populated as follows:
	deployment environments flexibility for populating the fields in the
	COSE_KDF_Context structure is provided.
	For better interoperability, the following recommended settings are
	provided:
	* PartyUInfo.identity corresponds to the kid found in the		* PartyUInfo.identity corresponds to the kid found in the
	COSE_Sign_Tagged or COSE_Sign1_Tagged structure (when a digital		COSE_Sign_Tagged or COSE_Sign1_Tagged structure (when a digital
	signature is used). When utilizing a MAC, then the kid is found		signature is used). When utilizing a MAC, then the kid is found
	in the COSE_Mac_Tagged or COSE_Mac0_Tagged structure.		in the COSE_Mac_Tagged or COSE_Mac0_Tagged structure.
	* PartyVInfo.identity corresponds to the kid used for the respective		* PartyVInfo.identity corresponds to the kid used for the respective
	recipient from the inner-most recipients array.		recipient from the inner-most recipients array.
	* The value in the AlgorithmID field corresponds to the alg		* The value in the AlgorithmID field corresponds to the alg
	parameter in the protected structure in the inner-most recipients		parameter in the unprotected header structure of the recipient
	array.		structure.
	* keyDataLength is set to the number of bits of the desired output		* keyDataLength is set to the number of bits of the desired output
	value.		value.
	* protected refers to the protected structure of the inner-most		* protected refers to the protected structure of the inner-most
	array.		array.
	4. Example		4. Example
	An example of the COSE_Encrypt structure using the HPKE scheme is		An example of the COSE_Encrypt structure using the HPKE scheme is
	shown in Figure 3. It uses the following algorithm combination:		shown in Figure 3. Line breaks and comments have been inserted for
			better readability. It uses the following algorithm combination:
	* AES-GCM-128 for encryption of detached ciphertext.		* AES-GCM-128 for encryption of detached ciphertext in layer 0.
	* AES-GCM-128 for encryption of the CEK.		* AES-GCM-128 for encryption of the CEK in layer 1 as well as ECDH
			with NIST P-256 and HKDF-SHA256 as a Key Encapsulation Mechanism
			(KEM).
	* Key Encapsulation Mechanism (KEM): NIST P-256		The algorithm selection is based on the registry of the values
			offered by the alg parameters.
	* Key Derivation Function (KDF): HKDF-SHA256		96_0([
	96(		/ protected header with alg=AES-GCM-128 /
			h'a10101',
			/ unprotected header with nonce /
			{5: h'938b528516193cc7123ff037809f4c2a'},
			/ detached ciphertext /
			null,
			/ recipient structure /
	[		[
	// protected field with alg=AES-GCM-128		/ protected field with alg for HPKE /
	h'A10101',		h'a1013863',
	{ // unprotected field with iv		/ unprotected header /
	5: h'26682306D4FB28CA01B43B80'		{
			/ ephemeral public key with x / y coodinate /
			-1: h'a401022001215820a596f2ca8d159c04942308ca90
			cfbfca65b108ca127df8fe191a063d00d7c5172258
			20aef47a45d6d6c572e7bd1b9f3e69b50ad3875c68
			f6da0caaa90c675df4162c39',
			/ kid for recipient static ECDH public key /
			4: h'6b69642d32',
	},		},
	// null because of detached ciphertext		/ encrypted CEK /
	null,		h'9aba6fa44e9b2cef9d646614dcda670dbdb31a3b9d37c7a
	[ // COSE_recipient_outer		65b099a8152533062',
	h'', // empty protected field		],
	{ // unprotected field with ...		])
	1: 1 // alg=A128GCM
	},
	// Encrypted CEK
	h'FA55A50CF110908DA6443149F2C2062011A7D8333A72721A',
	/ recipients / [ // COSE_recipient_inner
	[
	/ protected / h'a1013818' / {
	\ alg \ 1:TBD1 \ HPKE/P-256+HKDF-256 \
	} / ,
	/ unprotected / {
	// HPKE encapsulated key
	/ ephemeral / -1:{
	/ kty / 1:2,
	/ crv / -1:1,
	/ x / -2:h'98f50a4ff6c05861c8...90bbf91d6280',
	/ y / -3:true
	},
	// kid for recipient static ECDH public key
	/ kid / 4:'meriadoc.brandybuck@buckland.example'
	},
	// empty ciphertext
	/ ciphertext / h''
	]
	]
	]
	]
	)
	Figure 3: COSE_Encrypt Example for HPKE		Figure 3: COSE_Encrypt Example for HPKE
			Note that the COSE_Sign1 wrapper outside the COSE_Encrypt structure
			is not shown in the example above.
	5. Security Considerations		5. Security Considerations
	This specification is based on HPKE and the security considerations		This specification is based on HPKE and the security considerations
	of HPKE [I-D.irtf-cfrg-hpke] are therefore applicable also to this		of HPKE [I-D.irtf-cfrg-hpke] are therefore applicable also to this
	specification.		specification.
	HPKE assumes that the sender is in possession of the public key of		HPKE assumes the sender is in possession of the public key of the
	the recipient. A system using HPKE COSE has to assume the same		recipient and HPKE COSE makes the same assumptions. Some form of
	assumptions and public key distribution mechanism is assumed to		public key distribution mechanism is assumed to exist.
	exist.
	Since the CEK is randomly generated it must be ensured that the		Since the CEK is randomly generated it must be ensured that the
	guidelines for random number generations are followed, see [RFC8937].		guidelines for random number generations are followed, see [RFC8937].
	The SUIT_Encryption_Info structure shown in this document does not		The COSE_Encrypt structure must be authenticated using COSE
	provide authentication. Hence, the SUIT_Encryption_Info structure		constructs like COSE_Sign, or COSE_Sign1.
	has to be used in combination with other COSE constructs, such as the
	COSE_Sign or COSE_Sign1.
	6. IANA Considerations		6. IANA Considerations
	This document requests IANA to create new entries in the COSE		This document requests IANA to add new values to the COSE Algorithms
	Algorithms registry established with [RFC8152].		registry defined in [RFC8152] (in the Standards Action With Expert
			Review category):
	+-------------+-------+---------+------------+--------+---------------+		6.1. HPKE/P-256+HKDF-256 and AES-128-GCM
	| Name | Value | KDF | Ephemeral- | Key | Description |
	| | | | Static | Wrap | |
	+-------------+-------+---------+------------+--------+---------------+
	| HPKE/P-256+ | TBD1 | HKDF - | yes | none | HPKE with |
	| HKDF-256 | | SHA-256 | | | ECDH-ES |
	| | | | | | (P-256) + |
	| | | | | | HKDF-256 |
	+-------------+-------+---------+------------+--------+---------------+
	| HPKE/P-384+ | TBD2 | HKDF - | yes | none | HPKE with |
	| HKDF-SHA384 | | SHA-384 | | | ECDH-ES |
	| | | | | | (P-384) + |
	| | | | | | HKDF-384 |
	+-------------+-------+---------+------------+--------+---------------+
	| HPKE/P-521+ | TBD3 | HKDF - | yes | none | HPKE with |
	| HKDF-SHA521 | | SHA-521 | | | ECDH-ES |
	| | | | | | (P-521) + |
	| | | | | | HKDF-521 |
	+-------------+-------+---------+------------+--------+---------------+
	| HPKE | TBD4 | HKDF - | yes | none | HPKE with |
	| X25519 + | | SHA-256 | | | ECDH-ES |
	| HKDF-SHA256 | | | | | (X25519) + |
	| | | | | | HKDF-256 |
	+-------------+-------+---------+------------+--------+---------------+
	| HPKE | TBD4 | HKDF - | yes | none | HPKE with |
	| X448 + | | SHA-512 | | | ECDH-ES |
	| HKDF-SHA512 | | | | | (X448) + |
	| | | | | | HKDF-512 |
	+-------------+-------+---------+------------+--------+---------------+
	7. References		* Name: HPKE_P256_HKDF256_AES128_GCM
			* Value: TBD1
			* Description: HPKE/P-256+HKDF-256 and AES-128-GCM
			* Capabilities: [kty]
			* Change Controller: IESG
			* Reference: [[TBD: This RFC]]
			* Recommended: Yes
			6.2. HPKE/P-512+HKDF-512 and AES-256-GCM
			* Name: HPKE_P521_HKDF512_AES256_GCM
			* Value: TBD2
			* Description: HPKE/P-512+HKDF-512 and AES-256-GCM
			* Capabilities: [kty]
			* Change Controller: IESG
			* Reference: [[TBD: This RFC]]
			* Recommended: Yes
			TBD: More values to be added.
			7. References
	7.1. Normative References		7.1. Normative References
	[I-D.irtf-cfrg-hpke]		[I-D.irtf-cfrg-hpke]
	Barnes, R. L., Bhargavan, K., Lipp, B., and C. A. Wood,		Barnes, R. L., Bhargavan, K., Lipp, B., and C. A. Wood,
	"Hybrid Public Key Encryption", Work in Progress,		"Hybrid Public Key Encryption", Work in Progress,
	Internet-Draft, draft-irtf-cfrg-hpke-12, 2 September 2021,		Internet-Draft, draft-irtf-cfrg-hpke-12, 2 September 2021,
	<https://www.ietf.org/archive/id/draft-irtf-cfrg-hpke-		<https://www.ietf.org/archive/id/draft-irtf-cfrg-hpke-
	12.txt>.		12.txt>.
	[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate		[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
	skipping to change at page 9, line 42 ¶		skipping to change at page 9, line 39 ¶
	DOI 10.17487/RFC2630, June 1999,		DOI 10.17487/RFC2630, June 1999,
	<https://www.rfc-editor.org/info/rfc2630>.		<https://www.rfc-editor.org/info/rfc2630>.
	[RFC8937] Cremers, C., Garratt, L., Smyshlyaev, S., Sullivan, N.,		[RFC8937] Cremers, C., Garratt, L., Smyshlyaev, S., Sullivan, N.,
	and C. Wood, "Randomness Improvements for Security		and C. Wood, "Randomness Improvements for Security
	Protocols", RFC 8937, DOI 10.17487/RFC8937, October 2020,		Protocols", RFC 8937, DOI 10.17487/RFC8937, October 2020,
	<https://www.rfc-editor.org/info/rfc8937>.		<https://www.rfc-editor.org/info/rfc8937>.
	Appendix A. Acknowledgements		Appendix A. Acknowledgements
	TBD: Add your name here.		We would like to thank Goeran Selander, John Mattsson and Ilari
			Liusvaara for their review feedback.
	Authors' Addresses		Authors' Addresses
	Hannes Tschofenig		Hannes Tschofenig
	Arm Limited		Arm Limited
	Email: hannes.tschofenig@arm.com		Email: hannes.tschofenig@arm.com
	Russ Housley		Russ Housley
	Vigil Security, LLC		Vigil Security, LLC
	Email: housley@vigilsec.com		Email: housley@vigilsec.com
	Brendan Moran		Brendan Moran
	Arm Limited		Arm Limited
	Email: Brendan.Moran@arm.com		Email: Brendan.Moran@arm.com
End of changes. 50 change blocks.
	150 lines changed or deleted		156 lines changed or added
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