draft-ietf-httpbis-encryption-encoding-02.txt   draft-ietf-httpbis-encryption-encoding-03.txt 
HTTP Working Group M. Thomson HTTP Working Group M. Thomson
Internet-Draft Mozilla Internet-Draft Mozilla
Intended status: Standards Track June 29, 2016 Intended status: Standards Track October 9, 2016
Expires: December 31, 2016 Expires: April 12, 2017
Encrypted Content-Encoding for HTTP Encrypted Content-Encoding for HTTP
draft-ietf-httpbis-encryption-encoding-02 draft-ietf-httpbis-encryption-encoding-03
Abstract Abstract
This memo introduces a content-coding for HTTP that allows message This memo introduces a content coding for HTTP that allows message
payloads to be encrypted. payloads to be encrypted.
Note to Readers Note to Readers
Discussion of this draft takes place on the HTTP working group Discussion of this draft takes place on the HTTP working group
mailing list (ietf-http-wg@w3.org), which is archived at mailing list (ietf-http-wg@w3.org), which is archived at
https://lists.w3.org/Archives/Public/ietf-http-wg/ . https://lists.w3.org/Archives/Public/ietf-http-wg/ .
Working Group information can be found at http://httpwg.github.io/ ; Working Group information can be found at http://httpwg.github.io/ ;
source code and issues list for this draft can be found at source code and issues list for this draft can be found at
skipping to change at page 1, line 41 skipping to change at page 1, line 41
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 http://datatracker.ietf.org/drafts/current/. Drafts is at http://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 December 31, 2016. This Internet-Draft will expire on April 12, 2017.
Copyright Notice Copyright Notice
Copyright (c) 2016 IETF Trust and the persons identified as the Copyright (c) 2016 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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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
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described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Notational Conventions . . . . . . . . . . . . . . . . . 4 1.1. Notational Conventions . . . . . . . . . . . . . . . . . 3
2. The "aesgcm" HTTP Content Encoding . . . . . . . . . . . . . 4 2. The "aesgcm" HTTP Content Coding . . . . . . . . . . . . . . 4
3. The Encryption HTTP Header Field . . . . . . . . . . . . . . 6 3. The Encryption HTTP Header Field . . . . . . . . . . . . . . 6
3.1. Encryption Header Field Parameters . . . . . . . . . . . 6 3.1. Encryption Header Field Parameters . . . . . . . . . . . 6
3.2. Content Encryption Key Derivation . . . . . . . . . . . . 7 3.2. Content Encryption Key Derivation . . . . . . . . . . . . 7
3.3. Nonce Derivation . . . . . . . . . . . . . . . . . . . . 8 3.3. Nonce Derivation . . . . . . . . . . . . . . . . . . . . 8
4. Crypto-Key Header Field . . . . . . . . . . . . . . . . . . . 8 4. Crypto-Key Header Field . . . . . . . . . . . . . . . . . . . 8
4.1. Explicit Key . . . . . . . . . . . . . . . . . . . . . . 9 5. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 9
4.2. Diffie-Hellman . . . . . . . . . . . . . . . . . . . . . 9 5.1. Encryption of a Response . . . . . . . . . . . . . . . . 9
4.3. Pre-shared Authentication Secrets . . . . . . . . . . . . 11 5.2. Encryption with Multiple Records . . . . . . . . . . . . 10
5. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 11 5.3. Encryption and Compression . . . . . . . . . . . . . . . 10
5.1. Successful GET Response . . . . . . . . . . . . . . . . . 12 5.4. Encryption with More Than One Key . . . . . . . . . . . . 11
5.2. Encryption and Compression . . . . . . . . . . . . . . . 12 6. Security Considerations . . . . . . . . . . . . . . . . . . . 11
5.3. Encryption with More Than One Key . . . . . . . . . . . . 12 6.1. Key and Nonce Reuse . . . . . . . . . . . . . . . . . . . 11
5.4. Encryption with Explicit Key . . . . . . . . . . . . . . 13 6.2. Data Encryption Limits . . . . . . . . . . . . . . . . . 12
5.5. Encryption with Multiple Records . . . . . . . . . . . . 13 6.3. Content Integrity . . . . . . . . . . . . . . . . . . . . 12
5.6. Diffie-Hellman Encryption . . . . . . . . . . . . . . . . 14 6.4. Leaking Information in Headers . . . . . . . . . . . . . 12
5.7. Diffie-Hellman with Authentication Secret . . . . . . . . 14 6.5. Poisoning Storage . . . . . . . . . . . . . . . . . . . . 13
6. Security Considerations . . . . . . . . . . . . . . . . . . . 15 6.6. Sizing and Timing Attacks . . . . . . . . . . . . . . . . 13
6.1. Key and Nonce Reuse . . . . . . . . . . . . . . . . . . . 15 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13
6.2. Data Encryption Limits . . . . . . . . . . . . . . . . . 16 7.1. The "aesgcm" HTTP Content Coding . . . . . . . . . . . . 13
6.3. Content Integrity . . . . . . . . . . . . . . . . . . . . 16 7.2. Encryption Header Fields . . . . . . . . . . . . . . . . 14
6.4. Leaking Information in Headers . . . . . . . . . . . . . 16 7.3. The HTTP Encryption Parameter Registry . . . . . . . . . 14
6.5. Poisoning Storage . . . . . . . . . . . . . . . . . . . . 17 7.3.1. keyid . . . . . . . . . . . . . . . . . . . . . . . . 15
6.6. Sizing and Timing Attacks . . . . . . . . . . . . . . . . 17 7.3.2. salt . . . . . . . . . . . . . . . . . . . . . . . . 15
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17 7.3.3. rs . . . . . . . . . . . . . . . . . . . . . . . . . 15
7.1. The "aesgcm" HTTP Content Encoding . . . . . . . . . . . 17 7.4. The HTTP Crypto-Key Parameter Registry . . . . . . . . . 15
7.2. Encryption Header Fields . . . . . . . . . . . . . . . . 18 7.4.1. keyid . . . . . . . . . . . . . . . . . . . . . . . . 16
7.3. The HTTP Encryption Parameter Registry . . . . . . . . . 18 7.4.2. aesgcm . . . . . . . . . . . . . . . . . . . . . . . 16
7.3.1. keyid . . . . . . . . . . . . . . . . . . . . . . . . 19 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 16
7.3.2. salt . . . . . . . . . . . . . . . . . . . . . . . . 19 8.1. Normative References . . . . . . . . . . . . . . . . . . 16
7.3.3. rs . . . . . . . . . . . . . . . . . . . . . . . . . 19 8.2. Informative References . . . . . . . . . . . . . . . . . 17
7.4. The HTTP Crypto-Key Parameter Registry . . . . . . . . . 19 Appendix A. JWE Mapping . . . . . . . . . . . . . . . . . . . . 18
7.4.1. keyid . . . . . . . . . . . . . . . . . . . . . . . . 20 Appendix B. Acknowledgements . . . . . . . . . . . . . . . . . . 19
7.4.2. aesgcm . . . . . . . . . . . . . . . . . . . . . . . 20 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 19
7.4.3. dh . . . . . . . . . . . . . . . . . . . . . . . . . 20
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 20
8.1. Normative References . . . . . . . . . . . . . . . . . . 20
8.2. Informative References . . . . . . . . . . . . . . . . . 21
Appendix A. JWE Mapping . . . . . . . . . . . . . . . . . . . . 22
Appendix B. Intermediate Values for Encryption . . . . . . . . . 23
Appendix C. Acknowledgements . . . . . . . . . . . . . . . . . . 24
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 24
1. Introduction 1. Introduction
It is sometimes desirable to encrypt the contents of a HTTP message It is sometimes desirable to encrypt the contents of a HTTP message
(request or response) so that when the payload is stored (e.g., with (request or response) so that when the payload is stored (e.g., with
a HTTP PUT), only someone with the appropriate key can read it. a HTTP PUT), only someone with the appropriate key can read it.
For example, it might be necessary to store a file on a server For example, it might be necessary to store a file on a server
without exposing its contents to that server. Furthermore, that same without exposing its contents to that server. Furthermore, that same
file could be replicated to other servers (to make it more resistant file could be replicated to other servers (to make it more resistant
to server or network failure), downloaded by clients (to make it to server or network failure), downloaded by clients (to make it
available offline), etc. without exposing its contents. available offline), etc. without exposing its contents.
These uses are not met by the use of TLS [RFC5246], since it only These uses are not met by the use of TLS [RFC5246], since it only
encrypts the channel between the client and server. encrypts the channel between the client and server.
This document specifies a content-coding (Section 3.1.2 of [RFC7231]) This document specifies a content coding (Section 3.1.2 of [RFC7231])
for HTTP to serve these and other use cases. for HTTP to serve these and other use cases.
This content-coding is not a direct adaptation of message-based This content coding is not a direct adaptation of message-based
encryption formats - such as those that are described by [RFC4880], encryption formats - such as those that are described by [RFC4880],
[RFC5652], [RFC7516], and [XMLENC] - which are not suited to stream [RFC5652], [RFC7516], and [XMLENC] - which are not suited to stream
processing, which is necessary for HTTP. The format described here processing, which is necessary for HTTP. The format described here
cleaves more closely to the lower level constructs described in cleaves more closely to the lower level constructs described in
[RFC5116]. [RFC5116].
To the extent that message-based encryption formats use the same To the extent that message-based encryption formats use the same
primitives, the format can be considered as sequence of encrypted primitives, the format can be considered as sequence of encrypted
messages with a particular profile. For instance, Appendix A messages with a particular profile. For instance, Appendix A
explains how the format is congruent with a sequence of JSON Web explains how the format is congruent with a sequence of JSON Web
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Key header field that can be used to convey keying material. Key header field that can be used to convey keying material.
1.1. Notational Conventions 1.1. Notational Conventions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119]. document are to be interpreted as described in [RFC2119].
Base64url encoding is defined in Section 2 of [RFC7515]. Base64url encoding is defined in Section 2 of [RFC7515].
2. The "aesgcm" HTTP Content Encoding 2. The "aesgcm" HTTP Content Coding
The "aesgcm" HTTP content-coding indicates that a payload has been The "aesgcm" HTTP content coding indicates that a payload has been
encrypted using Advanced Encryption Standard (AES) in Galois/Counter encrypted using Advanced Encryption Standard (AES) in Galois/Counter
Mode (GCM) as identified as AEAD_AES_128_GCM in [RFC5116], Mode (GCM) as identified as AEAD_AES_128_GCM in [RFC5116],
Section 5.1. The AEAD_AES_128_GCM algorithm uses a 128 bit content Section 5.1. The AEAD_AES_128_GCM algorithm uses a 128 bit content
encryption key. encryption key.
When this content-coding is in use, the Encryption header field When this content coding is in use, the Encryption header field
(Section 3) describes how encryption has been applied. The Crypto- (Section 3) describes how encryption has been applied. The Crypto-
Key header field (Section 4) can be included to describe how the Key header field (Section 4) can be included to describe how the
content encryption key is derived or retrieved. content encryption key is derived or retrieved.
The "aesgcm" content-coding uses a single fixed set of encryption The "aesgcm" content coding uses a single fixed set of encryption
primitives. Cipher suite agility is achieved by defining a new primitives. Cipher suite agility is achieved by defining a new
content-coding scheme. This ensures that only the HTTP Accept- content coding scheme. This ensures that only the HTTP Accept-
Encoding header field is necessary to negotiate the use of Encoding header field is necessary to negotiate the use of
encryption. encryption.
The "aesgcm" content-coding uses a fixed record size. The resulting The "aesgcm" content coding uses a fixed record size. The resulting
encoding is either a single record, or a series of fixed-size encoding is either a single record, or a series of fixed-size
records. The final record, or a lone record, MUST be shorter than records. The final record, or a lone record, MUST be shorter than
the fixed record size. the fixed record size.
+-----------+ content is rs octets minus padding +-----------+ content is rs octets minus padding
| data | of between 2 and 65537 octets; | data | of between 2 and 65537 octets;
+-----------+ the last record is smaller +-----------+ the last record is smaller
| |
v v
+-----+-----------+ add padding to get rs octets; +-----+-----------+ add padding to get rs octets;
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by arbitrary amounts cannot increase the record size beyond 65537 by arbitrary amounts cannot increase the record size beyond 65537
octets. octets.
Applications that don't depending on streaming, random access, or Applications that don't depending on streaming, random access, or
arbitrary padding can use larger records, or even a single record. A arbitrary padding can use larger records, or even a single record. A
larger record size reduces the processing and data overheads. larger record size reduces the processing and data overheads.
3. The Encryption HTTP Header Field 3. The Encryption HTTP Header Field
The "Encryption" HTTP header field describes the encrypted content The "Encryption" HTTP header field describes the encrypted content
encoding(s) that have been applied to a payload body, and therefore coding(s) that have been applied to a payload body, and therefore how
how those content encoding(s) can be removed. those content coding(s) can be removed.
The "Encryption" header field uses the extended ABNF syntax defined The "Encryption" header field uses the extended ABNF syntax defined
in Section 1.2 of [RFC7230] and the "parameter" and "OWS" rules from in Section 1.2 of [RFC7230] and the "parameter" and "OWS" rules from
[RFC7231]. [RFC7231].
Encryption = #encryption_params Encryption = #encryption_params
encryption_params = [ parameter *( OWS ";" OWS parameter ) ] encryption_params = [ parameter *( OWS ";" OWS parameter ) ]
If the payload is encrypted more than once (as reflected by having If the payload is encrypted more than once (as reflected by having
multiple content-codings that imply encryption), each application of multiple content codings that imply encryption), each application of
the content encoding is reflected in a separate Encryption header the content coding is reflected in a separate Encryption header field
field value in the order in which they were applied. value in the order in which they were applied.
Encryption header field values with multiple instances of the same Encryption header field values with multiple instances of the same
parameter name are invalid. parameter name are invalid.
Servers processing PUT requests MUST persist the value of the Servers processing PUT requests MUST persist the value of the
Encryption header field, unless they remove the content-coding by Encryption header field, unless they remove the content coding by
decrypting the payload. decrypting the payload.
3.1. Encryption Header Field Parameters 3.1. Encryption Header Field Parameters
The following parameters are used in determining the content The following parameters are used in determining the content
encryption key that is used for encryption: encryption key that is used for encryption:
keyid: The "keyid" parameter identifies the keying material that is keyid: The "keyid" parameter identifies the keying material that is
used. When the Crypto-Key header field is used, the "keyid" used. When the Crypto-Key header field is used, the "keyid"
identifies a matching value in that field. The "keyid" parameter identifies a matching value in that field. The "keyid" parameter
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field is needed to derive the content encryption key. The "keyid" field is needed to derive the content encryption key. The "keyid"
parameter can also be used to identify keys in an application- parameter can also be used to identify keys in an application-
specific fashion. specific fashion.
salt: The "salt" parameter contains a base64url-encoded octets salt: The "salt" parameter contains a base64url-encoded octets
[RFC7515] that is used as salt in deriving a unique content [RFC7515] that is used as salt in deriving a unique content
encryption key (see Section 3.2). The "salt" parameter MUST be encryption key (see Section 3.2). The "salt" parameter MUST be
present, and MUST be exactly 16 octets long when decoded. The present, and MUST be exactly 16 octets long when decoded. The
"salt" parameter MUST NOT be reused for two different payload "salt" parameter MUST NOT be reused for two different payload
bodies that have the same input keying material; generating a bodies that have the same input keying material; generating a
random salt for every application of the content encoding ensures random salt for every application of the content coding ensures
that content encryption key reuse is highly unlikely. that content encryption key reuse is highly unlikely.
rs: The "rs" parameter contains a positive decimal integer that rs: The "rs" parameter contains a positive decimal integer that
describes the record size in octets. This value MUST be greater describes the record size in octets. This value MUST be greater
than 1. For the "aesgcm" content encoding, this value MUST NOT be than 1. For the "aesgcm" content coding, this value MUST NOT be
greater than 2^36-31 (see Section 6.2). The "rs" parameter is greater than 2^36-31 (see Section 6.2). The "rs" parameter is
optional. If the "rs" parameter is absent, the record size optional. If the "rs" parameter is absent, the record size
defaults to 4096 octets. defaults to 4096 octets.
3.2. Content Encryption Key Derivation 3.2. Content Encryption Key Derivation
In order to allow the reuse of keying material for multiple different In order to allow the reuse of keying material for multiple different
HTTP messages, a content encryption key is derived for each message. HTTP messages, a content encryption key is derived for each message.
The content encryption key is derived from the decoded value of the The content encryption key is derived from the decoded value of the
"salt" parameter using the HMAC-based key derivation function (HKDF) "salt" parameter using the HMAC-based key derivation function (HKDF)
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PRK = HMAC-SHA-256(salt, IKM) PRK = HMAC-SHA-256(salt, IKM)
The info parameter to HKDF is set to the ASCII-encoded string The info parameter to HKDF is set to the ASCII-encoded string
"Content-Encoding: aesgcm", a single zero octet and an optional "Content-Encoding: aesgcm", a single zero octet and an optional
context string: context string:
cek_info = "Content-Encoding: aesgcm" || 0x00 || context cek_info = "Content-Encoding: aesgcm" || 0x00 || context
Unless otherwise specified, the context is a zero length octet Unless otherwise specified, the context is a zero length octet
sequence. Specifications that use this content encoding MAY specify sequence. Specifications that use this content coding MAY specify
the use of an expanded context to cover additional inputs in the key the use of an expanded context to cover additional inputs in the key
derivation. derivation.
AEAD_AES_128_GCM requires a 16 octet (128 bit) content encryption key AEAD_AES_128_GCM requires a 16 octet (128 bit) content encryption key
(CEK), so the length (L) parameter to HKDF is 16. The second step of (CEK), so the length (L) parameter to HKDF is 16. The second step of
HKDF can therefore be simplified to the first 16 octets of a single HKDF can therefore be simplified to the first 16 octets of a single
HMAC: HMAC:
CEK = HMAC-SHA-256(PRK, cek_info || 0x01) CEK = HMAC-SHA-256(PRK, cek_info || 0x01)
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The input keying material and salt values are input to HKDF with The input keying material and salt values are input to HKDF with
different info and length parameters. different info and length parameters.
The length (L) parameter is 12 octets. The info parameter for the The length (L) parameter is 12 octets. The info parameter for the
nonce is the ASCII-encoded string "Content-Encoding: nonce", a single nonce is the ASCII-encoded string "Content-Encoding: nonce", a single
zero octet and an context: zero octet and an context:
nonce_info = "Content-Encoding: nonce" || 0x00 || context nonce_info = "Content-Encoding: nonce" || 0x00 || context
The context for nonce derivation SHOULD be the same as is used for The context for nonce derivation is the same as is used for content
content encryption key derivation. encryption key derivation.
The result is combined with the record sequence number - using The result is combined with the record sequence number - using
exclusive or - to produce the nonce. The record sequence number exclusive or - to produce the nonce. The record sequence number
(SEQ) is a 96-bit unsigned integer in network byte order that starts (SEQ) is a 96-bit unsigned integer in network byte order that starts
at zero. at zero.
Thus, the final nonce for each record is a 12 octet value: Thus, the final nonce for each record is a 12 octet value:
NONCE = HMAC-SHA-256(PRK, nonce_info || 0x01) XOR SEQ NONCE = HMAC-SHA-256(PRK, nonce_info || 0x01) XOR SEQ
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[RFC7231]. [RFC7231].
Crypto-Key = #crypto_key_params Crypto-Key = #crypto_key_params
crypto_key_params = [ parameter *( OWS ";" OWS parameter ) ] crypto_key_params = [ parameter *( OWS ";" OWS parameter ) ]
keyid: The "keyid" parameter corresponds to the "keyid" parameter in keyid: The "keyid" parameter corresponds to the "keyid" parameter in
the Encryption header field. the Encryption header field.
aesgcm: The "aesgcm" parameter contains the base64url-encoded octets aesgcm: The "aesgcm" parameter contains the base64url-encoded octets
[RFC7515] of the input keying material for the "aesgcm" content [RFC7515] of the input keying material for the "aesgcm" content
encoding. coding.
dh: The "dh" parameter contains an ephemeral Diffie-Hellman share.
This form of the header field can be used to encrypt content for a
specific recipient.
Crypto-Key header field values with multiple instances of the same Crypto-Key header field values with multiple instances of the same
parameter name are invalid. parameter name are invalid.
The input keying material used by the key derivation (see The input keying material used by the key derivation (see
Section 3.2) can be determined based on the information in the Section 3.2) can be determined based on the information in the
Crypto-Key header field. The method for key derivation depends on Crypto-Key header field.
the parameters that are present in the header field.
The value or values provided in the Crypto-Key header field is valid The value or values provided in the Crypto-Key header field is valid
only for the current HTTP message unless additional information only for the current HTTP message unless additional information
indicates a greater scope. indicates a greater scope.
Note that different methods for determining input keying material
will produce different amounts of data. The HKDF process ensures
that the final content encryption key is the necessary size.
Alternative methods for determining input keying material MAY be Alternative methods for determining input keying material MAY be
defined by specifications that use this content-encoding. defined by specifications that use this content coding. This
document only defines the use of the "aesgcm" parameter which
4.1. Explicit Key describes an explicit key.
The "aesgcm" parameter is decoded and used as the input keying
material for the "aesgcm" content encoding. The "aesgcm" parameter
MUST decode to at least 16 octets in order to be used as input keying
material for "aesgcm" content encoding.
Other key determination parameters can be ignored if the "aesgcm"
parameter is present.
4.2. Diffie-Hellman
The "dh" parameter is included to describe a Diffie-Hellman share,
either modp (or finite field) Diffie-Hellman [DH] or elliptic curve
Diffie-Hellman (ECDH) [RFC4492].
This share is combined with other information at the recipient to
determine the HKDF input keying material. In order for the exchange
to be successful, the following information MUST be established out
of band:
o Which Diffie-Hellman form is used.
o The modp group or elliptic curve that will be used.
o A label that uniquely identifies the group. This label will be
expressed as a sequence of octets and MUST NOT include a zero-
valued octet.
o The format of the ephemeral public share that is included in the
"dh" parameter. This encoding MUST result in a single, canonical
sequence of octets. For instance, using ECDH both parties need to
agree whether this is an uncompressed or compressed point.
In addition to identifying which content-encoding this input keying
material is used for, the "keyid" parameter is used to identify this
additional information at the receiver.
The intended recipient recovers their private key and are then able
to generate a shared secret using the designated Diffie-Hellman
process.
The context for content encryption key and nonce derivation (see
Section 3.2) is set to include the means by which the keys were
derived. The context is formed from the concatenation of group
label, a single zero octet, the length of the public key of the
recipient, the public key of the recipient, the length of the public
key of the sender, and the public key of the sender. The public keys
are encoded into octets as defined for the group when determining the
context string.
context = label || 0x00 ||
length(recipient_public) || recipient_public ||
length(sender_public) || sender_public
The two length fields are encoded as a two octet unsigned integer in
network byte order.
Specifications that rely on an Diffie-Hellman exchange for
determining input keying material MUST either specify the parameters
for Diffie-Hellman (label, group parameters, or curves and point
format) that are used, or describe how those parameters are
negotiated between sender and receiver.
4.3. Pre-shared Authentication Secrets
Key derivation MAY be extended to include an additional The "aesgcm" parameter MUST decode to at least 16 octets in order to
authentication secret. Such a secret is shared between the sender be used as input keying material for "aesgcm" content coding.
and receiver of a message using other means.
A pre-shared authentication secret is not explicitly signaled in 5. Examples
either the Encryption or Crypto-Key header fields. Use of this
additional step depends on prior agreement.
When a shared authentication secret is used, the keying material This section shows a few examples of the encrypted content coding.
produced by the key agreement method (e.g., Diffie-Hellman, explicit
key, or otherwise) is combined with the authentication secret using
HKDF. The output of HKDF is the input keying material used to derive
the content encryption key and nonce Section 3.2.
The authentication secret is used as the "salt" parameter to HKDF, Note: All binary values in the examples in this section use base64url
the raw keying material (e.g., Diffie-Hellman output) is used as the encoding [RFC7515]. This includes the bodies of requests.
"IKM" parameter, the ASCII-encoded string "Content-Encoding: auth" Whitespace and line wrapping is added to fit formatting constraints.
with a terminal zero octet is used as the "info" parameter, and the
length of the output is 32 octets (i.e., the entire output of the
underlying SHA-256 HMAC function):
auth_info = "Content-Encoding: auth" || 0x00 5.1. Encryption of a Response
IKM = HKDF(authentication, raw_key, auth_info, 32)
This invocation of HKDF does not take the same context that is Here, a successful HTTP GET response has been encrypted using input
provided to the final key derivation stages. Alternatively, this keying material that is identified by a URI.
phase can be viewed as always having a zero-length context.
Note that in the absence of an authentication secret, the input The encrypted data in this example is the UTF-8 encoded string "I am
keying material is simply the raw keying material: the walrus". The input keying material is included in the Crypto-Key
header field. The content body contains a single record only and is
shown here using base64url encoding for presentation reasons.
IKM = raw_key HTTP/1.1 200 OK
Content-Type: application/octet-stream
Content-Length: 33
Content-Encoding: aesgcm
Encryption: keyid="a1"; salt="vr0o6Uq3w_KDWeatc27mUg"
Crypto-Key: keyid="a1"; aesgcm="csPJEXBYA5U-Tal9EdJi-w"
5. Examples VDeU0XxaJkOJDAxPl7h9JD5V8N43RorP7PfpPdZZQuwF
This section shows a few examples of the content encoding. Note that the media type has been changed to "application/octet-
stream" to avoid exposing information about the content.
Note: All binary values in the examples in this section use the URL 5.2. Encryption with Multiple Records
and filename safe variant of base64 [RFC4648]. This includes the
bodies of requests. Whitespace in these values is added to fit
formatting constraints.
5.1. Successful GET Response This example shows the same encrypted message, but split into records
of 10 octets each. The first record includes a single additional
octet of padding, which causes the end of the content to align with a
record boundary, forcing the creation of a third record that contains
only padding.
HTTP/1.1 200 OK HTTP/1.1 200 OK
Content-Type: application/octet-stream Content-Length: 70
Content-Encoding: aesgcm Content-Encoding: aesgcm
Connection: close Encryption: keyid="a1"; salt="4pdat984KmT9BWsU3np0nw"; rs=10
Encryption: keyid="bob/keys/123"; Crypto-Key: keyid="a1"; aesgcm="BO3ZVPxUlnLORbVGMpbT1Q"
salt="XZwpw6o37R-6qoZjw6KwAw"
[encrypted payload]
Here, a successful HTTP GET response has been encrypted using input
keying material that is identified by a URI.
Note that the media type has been changed to "application/octet- uzLfrZ4cbMTC6hlUqHz4NvWZshFlTN3o2RLr6FrIuOKEfl2VrM_jYgoiIyEo
stream" to avoid exposing information about the content. Zvc-ZGwV-RMJejG4M6ZfGysBAdhpPqrLzw
5.2. Encryption and Compression 5.3. Encryption and Compression
In this example, a response is first compressed, then encrypted. In this example, a response is first compressed, then encrypted.
Note that this particular encoding might compromise confidentiality Note that this particular encoding might compromise confidentiality
if the contents of the response could be influenced by an attacker. if the contents could be influenced by an attacker.
HTTP/1.1 200 OK HTTP/1.1 200 OK
Content-Type: text/html Content-Type: text/html
Content-Encoding: gzip, aesgcm Content-Encoding: gzip, aesgcm
Transfer-Encoding: chunked Transfer-Encoding: chunked
Encryption: keyid="me@example.com"; Encryption: keyid="me@example.com";
salt="m2hJ_NttRtFyUiMRPwfpHA" salt="m2hJ_NttRtFyUiMRPwfpHA"
[encrypted payload] [encrypted payload]
5.3. Encryption with More Than One Key 5.4. Encryption with More Than One Key
Here, a PUT request has been encrypted twice with different input Here, a PUT request has been encrypted twice with different input
keying material; decrypting twice is necessary to read the content. keying material; decrypting twice is necessary to read the content.
The outer layer of encryption uses a 1200 octet record size. The outer layer of encryption uses a 1200 octet record size.
PUT /thing HTTP/1.1 PUT /thing HTTP/1.1
Host: storage.example.com Host: storage.example.com
Content-Type: application/http Content-Type: application/http
Content-Encoding: aesgcm, aesgcm Content-Encoding: aesgcm, aesgcm
Content-Length: 1235 Content-Length: 1235
Encryption: keyid="mailto:me@example.com"; Encryption: keyid="mailto:me@example.com";
salt="NfzOeuV5USPRA-n_9s1Lag", salt="NfzOeuV5USPRA-n_9s1Lag",
keyid="bob/keys/123"; keyid="bob/keys/123";
salt="bDMSGoc2uobK_IhavSHsHA"; rs=1200 salt="bDMSGoc2uobK_IhavSHsHA"; rs=1200
[encrypted payload] [encrypted payload]
5.4. Encryption with Explicit Key
This example shows the UTF-8 encoded string "I am the walrus"
encrypted using an directly provided value for the input keying
material. The content body contains a single record only and is
shown here using base64url encoding for presentation reasons.
HTTP/1.1 200 OK
Content-Length: 33
Content-Encoding: aesgcm
Encryption: keyid="a1"; salt="vr0o6Uq3w_KDWeatc27mUg"
Crypto-Key: keyid="a1"; aesgcm="csPJEXBYA5U-Tal9EdJi-w"
VDeU0XxaJkOJDAxPl7h9JD5V8N43RorP7PfpPdZZQuwF
5.5. Encryption with Multiple Records
This example shows the same encrypted message, but split into records
of 10 octets each. The first record includes a single additional
octet of padding, which causes the end of the content to align with a
record boundary, forcing the creation of a third record that contains
only padding.
HTTP/1.1 200 OK
Content-Length: 70
Content-Encoding: aesgcm
Encryption: keyid="a1"; salt="4pdat984KmT9BWsU3np0nw"; rs=10
Crypto-Key: keyid="a1"; aesgcm="BO3ZVPxUlnLORbVGMpbT1Q"
uzLfrZ4cbMTC6hlUqHz4NvWZshFlTN3o2RLr6FrIuOKEfl2VrM_jYgoiIyEo
Zvc-ZGwV-RMJejG4M6ZfGysBAdhpPqrLzw
5.6. Diffie-Hellman Encryption
HTTP/1.1 200 OK
Content-Length: 33
Content-Encoding: aesgcm
Encryption: keyid="dhkey"; salt="Qg61ZJRva_XBE9IEUelU3A"
Crypto-Key: keyid="dhkey";
dh="BDgpRKok2GZZDmS4r63vbJSUtcQx4Fq1V58-6-3NbZzS
TlZsQiCEDTQy3CZ0ZMsqeqsEb7qW2blQHA4S48fynTk"
yqD2bapcx14XxUbtwjiGx69eHE3Yd6AqXcwBpT2Kd1uy
This example shows the same string, "I am the walrus", encrypted
using ECDH over the P-256 curve [FIPS186], which is identified with
the label "P-256" encoded in ASCII. The content body is shown here
encoded in URL-safe base64url for presentation reasons only.
The receiver (in this case, the HTTP client) uses a key pair that is
identified by the string "dhkey" and the sender (the server) uses a
key pair for which the public share is included in the "dh" parameter
above. The keys shown below use uncompressed points [X9.62] encoded
using base64url. Line wrapping is added for presentation purposes
only.
Receiver:
private key: 9FWl15_QUQAWDaD3k3l50ZBZQJ4au27F1V4F0uLSD_M
public key: BCEkBjzL8Z3C-oi2Q7oE5t2Np-p7osjGLg93qUP0wvqR
T21EEWyf0cQDQcakQMqz4hQKYOQ3il2nNZct4HgAUQU
Sender:
private key: vG7TmzUX9NfVR4XUGBkLAFu8iDyQe-q_165JkkN0Vlw
public key: <the value of the "dh" parameter>
5.7. Diffie-Hellman with Authentication Secret
This example shows the same receiver key pair from Section 5.6, but
with a shared authentication secret of "R29vIGdvbyBnJyBqb29iIQ".
HTTP/1.1 200 OK
Content-Length: 33
Content-Encoding: aesgcm
Encryption: keyid="dhkey"; salt="lngarbyKfMoi9Z75xYXmkg"
Crypto-Key: keyid="dhkey";
dh="BNoRDbb84JGm8g5Z5CFxurSqsXWJ11ItfXEWYVLE85Y7
CYkDjXsIEc4aqxYaQ1G8BqkXCJ6DPpDrWtdWj_mugHU"
6nqAQUME8hNqw5J3kl8cpVVJylXKYqZOeseZG8UueKpA
The sender's private key used in this example is "nCScek-QpEjmOOlT-
rQ38nZzvdPlqa00Zy0i6m2OJvY". Intermediate values for this example
are included in Appendix B.
6. Security Considerations 6. Security Considerations
This mechanism assumes the presence of a key management framework This mechanism assumes the presence of a key management framework
that is used to manage the distribution of keys between valid senders that is used to manage the distribution of keys between valid senders
and receivers. Defining key management is part of composing this and receivers. Defining key management is part of composing this
mechanism into a larger application, protocol, or framework. mechanism into a larger application, protocol, or framework.
Implementation of cryptography - and key management in particular - Implementation of cryptography - and key management in particular -
can be difficult. For instance, implementations need to account for can be difficult. For instance, implementations need to account for
the potential for exposing keying material on side channels, such as the potential for exposing keying material on side channels, such as
might be exposed by the time it takes to perform a given operation. might be exposed by the time it takes to perform a given operation.
The requirements for a good implementation of cryptographic The requirements for a good implementation of cryptographic
algorithms can change over time. algorithms can change over time.
6.1. Key and Nonce Reuse 6.1. Key and Nonce Reuse
Encrypting different plaintext with the same content encryption key Encrypting different plaintext with the same content encryption key
and nonce in AES-GCM is not safe [RFC5116]. The scheme defined here and nonce in AES-GCM is not safe [RFC5116]. The scheme defined here
uses a fixed progression of nonce values. Thus, a new content uses a fixed progression of nonce values. Thus, a new content
encryption key is needed for every application of the content encryption key is needed for every application of the content coding.
encoding. Since input keying material can be reused, a unique "salt" Since input keying material can be reused, a unique "salt" parameter
parameter is needed to ensure a content encryption key is not reused. is needed to ensure a content encryption key is not reused.
If a content encryption key is reused - that is, if input keying If a content encryption key is reused - that is, if input keying
material and salt are reused - this could expose the plaintext and material and salt are reused - this could expose the plaintext and
the authentication key, nullifying the protection offered by the authentication key, nullifying the protection offered by
encryption. Thus, if the same input keying material is reused, then encryption. Thus, if the same input keying material is reused, then
the salt parameter MUST be unique each time. This ensures that the the salt parameter MUST be unique each time. This ensures that the
content encryption key is not reused. An implementation SHOULD content encryption key is not reused. An implementation SHOULD
generate a random salt parameter for every message; a counter could generate a random salt parameter for every message; a counter could
achieve the same result. achieve the same result.
skipping to change at page 17, line 41 skipping to change at page 13, line 46
so on, may leak sensitive information. so on, may leak sensitive information.
This risk can be mitigated through the use of the padding that this This risk can be mitigated through the use of the padding that this
mechanism provides. Alternatively, splitting up content into mechanism provides. Alternatively, splitting up content into
segments and storing the separately might reduce exposure. HTTP/2 segments and storing the separately might reduce exposure. HTTP/2
[RFC7540] combined with TLS [RFC5246] might be used to hide the size [RFC7540] combined with TLS [RFC5246] might be used to hide the size
of individual messages. of individual messages.
7. IANA Considerations 7. IANA Considerations
7.1. The "aesgcm" HTTP Content Encoding 7.1. The "aesgcm" HTTP Content Coding
This memo registers the "aesgcm" HTTP content-coding in the HTTP This memo registers the "aesgcm" HTTP content coding in the HTTP
Content Codings Registry, as detailed in Section 2. Content Codings Registry, as detailed in Section 2.
o Name: aesgcm o Name: aesgcm
o Description: AES-GCM encryption with a 128-bit content encryption o Description: AES-GCM encryption with a 128-bit content encryption
key key
o Reference: this specification o Reference: this specification
7.2. Encryption Header Fields 7.2. Encryption Header Fields
This memo registers the "Encryption" HTTP header field in the This memo registers the "Encryption" HTTP header field in the
Permanent Message Header Registry, as detailed in Section 3. Permanent Message Header Registry, as detailed in Section 3.
skipping to change at page 20, line 18 skipping to change at page 16, line 20
o Purpose: Identify the key that is in use. o Purpose: Identify the key that is in use.
o Reference: this document o Reference: this document
7.4.2. aesgcm 7.4.2. aesgcm
o Parameter Name: aesgcm o Parameter Name: aesgcm
o Purpose: Provide an explicit input keying material value for the o Purpose: Provide an explicit input keying material value for the
aesgcm content encoding. aesgcm content coding.
o Reference: this document
7.4.3. dh
o Parameter Name: dh
o Purpose: Carry a modp or elliptic curve Diffie-Hellman share used
to derive input keying material.
o Reference: this document o Reference: this document
8. References 8. References
8.1. Normative References 8.1. Normative References
[DH] Diffie, W. and M. Hellman, "New Directions in
Cryptography", IEEE Transactions on Information Theory,
V.IT-22 n.6 , June 1977.
[FIPS180-4] [FIPS180-4]
Department of Commerce, National., "NIST FIPS 180-4, Department of Commerce, National., "NIST FIPS 180-4,
Secure Hash Standard", March 2012, Secure Hash Standard", March 2012,
<http://csrc.nist.gov/publications/fips/fips180-4/ <http://csrc.nist.gov/publications/fips/fips180-4/
fips-180-4.pdf>. fips-180-4.pdf>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>. <http://www.rfc-editor.org/info/rfc2119>.
[RFC4492] Blake-Wilson, S., Bolyard, N., Gupta, V., Hawk, C., and B.
Moeller, "Elliptic Curve Cryptography (ECC) Cipher Suites
for Transport Layer Security (TLS)", RFC 4492,
DOI 10.17487/RFC4492, May 2006,
<http://www.rfc-editor.org/info/rfc4492>.
[RFC5116] McGrew, D., "An Interface and Algorithms for Authenticated [RFC5116] McGrew, D., "An Interface and Algorithms for Authenticated
Encryption", RFC 5116, DOI 10.17487/RFC5116, January 2008, Encryption", RFC 5116, DOI 10.17487/RFC5116, January 2008,
<http://www.rfc-editor.org/info/rfc5116>. <http://www.rfc-editor.org/info/rfc5116>.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226,
DOI 10.17487/RFC5226, May 2008,
<http://www.rfc-editor.org/info/rfc5226>.
[RFC5869] Krawczyk, H. and P. Eronen, "HMAC-based Extract-and-Expand [RFC5869] Krawczyk, H. and P. Eronen, "HMAC-based Extract-and-Expand
Key Derivation Function (HKDF)", RFC 5869, Key Derivation Function (HKDF)", RFC 5869,
DOI 10.17487/RFC5869, May 2010, DOI 10.17487/RFC5869, May 2010,
<http://www.rfc-editor.org/info/rfc5869>. <http://www.rfc-editor.org/info/rfc5869>.
[RFC7230] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer [RFC7230] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
Protocol (HTTP/1.1): Message Syntax and Routing", Protocol (HTTP/1.1): Message Syntax and Routing",
RFC 7230, DOI 10.17487/RFC7230, June 2014, RFC 7230, DOI 10.17487/RFC7230, June 2014,
<http://www.rfc-editor.org/info/rfc7230>. <http://www.rfc-editor.org/info/rfc7230>.
skipping to change at page 21, line 41 skipping to change at page 17, line 26
Signature (JWS)", RFC 7515, DOI 10.17487/RFC7515, May Signature (JWS)", RFC 7515, DOI 10.17487/RFC7515, May
2015, <http://www.rfc-editor.org/info/rfc7515>. 2015, <http://www.rfc-editor.org/info/rfc7515>.
8.2. Informative References 8.2. Informative References
[AEBounds] [AEBounds]
Luykx, A. and K. Paterson, "Limits on Authenticated Luykx, A. and K. Paterson, "Limits on Authenticated
Encryption Use in TLS", March 2016, Encryption Use in TLS", March 2016,
<http://www.isg.rhul.ac.uk/~kp/TLS-AEbounds.pdf>. <http://www.isg.rhul.ac.uk/~kp/TLS-AEbounds.pdf>.
[FIPS186] National Institute of Standards and Technology (NIST),
"Digital Signature Standard (DSS)", NIST PUB 186-4 , July
2013.
[RFC4648] Josefsson, S., "The Base16, Base32, and Base64 Data
Encodings", RFC 4648, DOI 10.17487/RFC4648, October 2006,
<http://www.rfc-editor.org/info/rfc4648>.
[RFC4880] Callas, J., Donnerhacke, L., Finney, H., Shaw, D., and R. [RFC4880] Callas, J., Donnerhacke, L., Finney, H., Shaw, D., and R.
Thayer, "OpenPGP Message Format", RFC 4880, Thayer, "OpenPGP Message Format", RFC 4880,
DOI 10.17487/RFC4880, November 2007, DOI 10.17487/RFC4880, November 2007,
<http://www.rfc-editor.org/info/rfc4880>. <http://www.rfc-editor.org/info/rfc4880>.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226,
DOI 10.17487/RFC5226, May 2008,
<http://www.rfc-editor.org/info/rfc5226>.
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security [RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", RFC 5246, (TLS) Protocol Version 1.2", RFC 5246,
DOI 10.17487/RFC5246, August 2008, DOI 10.17487/RFC5246, August 2008,
<http://www.rfc-editor.org/info/rfc5246>. <http://www.rfc-editor.org/info/rfc5246>.
[RFC5652] Housley, R., "Cryptographic Message Syntax (CMS)", STD 70, [RFC5652] Housley, R., "Cryptographic Message Syntax (CMS)", STD 70,
RFC 5652, DOI 10.17487/RFC5652, September 2009, RFC 5652, DOI 10.17487/RFC5652, September 2009,
<http://www.rfc-editor.org/info/rfc5652>. <http://www.rfc-editor.org/info/rfc5652>.
[RFC7233] Fielding, R., Ed., Lafon, Y., Ed., and J. Reschke, Ed., [RFC7233] Fielding, R., Ed., Lafon, Y., Ed., and J. Reschke, Ed.,
skipping to change at page 22, line 38 skipping to change at page 18, line 10
[RFC7516] Jones, M. and J. Hildebrand, "JSON Web Encryption (JWE)", [RFC7516] Jones, M. and J. Hildebrand, "JSON Web Encryption (JWE)",
RFC 7516, DOI 10.17487/RFC7516, May 2015, RFC 7516, DOI 10.17487/RFC7516, May 2015,
<http://www.rfc-editor.org/info/rfc7516>. <http://www.rfc-editor.org/info/rfc7516>.
[RFC7540] Belshe, M., Peon, R., and M. Thomson, Ed., "Hypertext [RFC7540] Belshe, M., Peon, R., and M. Thomson, Ed., "Hypertext
Transfer Protocol Version 2 (HTTP/2)", RFC 7540, Transfer Protocol Version 2 (HTTP/2)", RFC 7540,
DOI 10.17487/RFC7540, May 2015, DOI 10.17487/RFC7540, May 2015,
<http://www.rfc-editor.org/info/rfc7540>. <http://www.rfc-editor.org/info/rfc7540>.
[X9.62] ANSI, "Public Key Cryptography For The Financial Services
Industry: The Elliptic Curve Digital Signature Algorithm
(ECDSA)", ANSI X9.62 , 1998.
[XMLENC] Eastlake, D., Reagle, J., Imamura, T., Dillaway, B., and [XMLENC] Eastlake, D., Reagle, J., Imamura, T., Dillaway, B., and
E. Simon, "XML Encryption Syntax and Processing", W3C E. Simon, "XML Encryption Syntax and Processing", W3C
REC , December 2002, <http://www.w3.org/TR/xmlenc-core/>. REC , December 2002, <http://www.w3.org/TR/xmlenc-core/>.
Appendix A. JWE Mapping Appendix A. JWE Mapping
The "aesgcm" content encoding can be considered as a sequence of JSON The "aesgcm" content coding can be considered as a sequence of JSON
Web Encryption (JWE) objects [RFC7516], each corresponding to a Web Encryption (JWE) objects [RFC7516], each corresponding to a
single fixed size record that includes leading padding. The single fixed size record that includes leading padding. The
following transformations are applied to a JWE object that might be following transformations are applied to a JWE object that might be
expressed using the JWE Compact Serialization: expressed using the JWE Compact Serialization:
o The JWE Protected Header is fixed to a value { "alg": "dir", o The JWE Protected Header is fixed to the value { "alg": "dir",
"enc": "A128GCM" }, describing direct encryption using AES-GCM "enc": "A128GCM" }, describing direct encryption using AES-GCM
with a 128-bit content encryption key. This header is not with a 128-bit content encryption key. This header is not
transmitted, it is instead implied by the value of the Content- transmitted, it is instead implied by the value of the Content-
Encoding header field. Encoding header field.
o The JWE Encrypted Key is empty, as stipulated by the direct o The JWE Encrypted Key is empty, as stipulated by the direct
encryption algorithm. encryption algorithm.
o The JWE Initialization Vector ("iv") for each record is set to the o The JWE Initialization Vector ("iv") for each record is set to the
exclusive or of the 96-bit record sequence number, starting at exclusive or of the 96-bit record sequence number, starting at
zero, and a value derived from the input keying material (see zero, and a value derived from the input keying material (see
Section 3.3). This value is also not transmitted. Section 3.3). This value is also not transmitted.
o The final value is the concatenated JWE Ciphertext and the JWE o The final value is the concatenated JWE Ciphertext and the JWE
Authentication Tag, both expressed without URL-safe Base 64 Authentication Tag, both expressed without base64url encoding.
encoding. The "." separator is omitted, since the length of these The "." separator is omitted, since the length of these fields is
fields is known. known.
Thus, the example in Section 5.4 can be rendered using the JWE Thus, the example in Section 5.1 can be rendered using the JWE
Compact Serialization as: Compact Serialization as:
eyAiYWxnIjogImRpciIsICJlbmMiOiAiQTEyOEdDTSIgfQ..31iQYc1v4a36EgyJ. eyAiYWxnIjogImRpciIsICJlbmMiOiAiQTEyOEdDTSIgfQ..31iQYc1v4a36EgyJ.
VDeU0XxaJkOJDAxPl7h9JD4.VfDeN0aKz-z36T3WWULsBQ VDeU0XxaJkOJDAxPl7h9JD4.VfDeN0aKz-z36T3WWULsBQ
Where the first line represents the fixed JWE Protected Header, an Where the first line represents the fixed JWE Protected Header, an
empty JWE Encrypted Key, and the algorithmically-determined JWE empty JWE Encrypted Key, and the algorithmically-determined JWE
Initialization Vector. The second line contains the encoded body, Initialization Vector. The second line contains the encoded body,
split into JWE Ciphertext and JWE Authentication Tag. split into JWE Ciphertext and JWE Authentication Tag.
Appendix B. Intermediate Values for Encryption Appendix B. Acknowledgements
The intermediate values calculated for the example in Section 5.7 are
shown here. The following are inputs to the calculation:
Plaintext: SSBhbSB0aGUgd2FscnVz
Sender public key: BNoRDbb84JGm8g5Z5CFxurSqsXWJ11ItfXEWYVLE85Y7
CYkDjXsIEc4aqxYaQ1G8BqkXCJ6DPpDrWtdWj_mugHU
Sender private key: nCScek-QpEjmOOlT-rQ38nZzvdPlqa00Zy0i6m2OJvY
Receiver public key: BCEkBjzL8Z3C-oi2Q7oE5t2Np-p7osjGLg93qUP0wvqR
T21EEWyf0cQDQcakQMqz4hQKYOQ3il2nNZct4HgAUQU
Receiver private key: 9FWl15_QUQAWDaD3k3l50ZBZQJ4au27F1V4F0uLSD_M
Salt: lngarbyKfMoi9Z75xYXmkg
Note that knowledge of just one of the private keys is necessary.
The sender randomly generates the salt value, whereas salt is input
to the receiver.
This produces the following intermediate values:
Shared secret (raw_key): RNjC-NVW4BGJbxWPW7G2mowsLeDa53LYKYm4-NOQ6Y
Input keying material (IKM): EhpZec37Ptm4IRD5-jtZ0q6r1iK5vYmY1tZwtN8
fbZY
Context for content encryption key derivation:
Q29udGVudC1FbmNvZGluZzogYWVzZ2NtAFAtMjU2AABB BCEkBjzL8Z3C-
oi2Q7oE5t2Np-p7osjGLg93qUP0wvqR
T21EEWyf0cQDQcakQMqz4hQKYOQ3il2nNZct4HgAUQUA
QQTaEQ22_OCRpvIOWeQhcbq0qrF1iddSLX1xFmFSxPOW
OwmJA417CBHOGqsWGkNRvAapFwiegz6Q61rXVo_5roB1
Content encryption key (CEK): AN2-xhvFWeYh5z0fcDu0Ww
Context for nonce derivation: Q29udGVudC1FbmNvZGluZzogbm9uY2UAUC0yNT
YAAEEE ISQGPMvxncL6iLZDugTm3Y2n6nuiyMYuD3epQ_TC-pFP
bUQRbJ_RxANBxqRAyrPiFApg5DeKXac1ly3geABRBQBB
BNoRDbb84JGm8g5Z5CFxurSqsXWJ11ItfXEWYVLE85Y7
CYkDjXsIEc4aqxYaQ1G8BqkXCJ6DPpDrWtdWj_mugHU
Base nonce: JY1Okw5rw1Drkg9J
When the CEK and nonce are used with AES GCM and the padded plaintext
of AABJIGFtIHRoZSB3YWxydXM, the final ciphertext is
6nqAQUME8hNqw5J3kl8cpVVJylXKYqZOeseZG8UueKpA, as shown in the
example.
Appendix C. Acknowledgements
Mark Nottingham was an original author of this document. Mark Nottingham was an original author of this document.
The following people provided valuable input: Richard Barnes, David The following people provided valuable input: Richard Barnes, David
Benjamin, Peter Beverloo, Mike Jones, Stephen Farrell, Adam Langley, Benjamin, Peter Beverloo, Mike Jones, Stephen Farrell, Adam Langley,
John Mattsson, Eric Rescorla, and Jim Schaad. John Mattsson, Eric Rescorla, and Jim Schaad.
Author's Address Author's Address
Martin Thomson Martin Thomson
Mozilla Mozilla
Email: martin.thomson@gmail.com Email: martin.thomson@gmail.com
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