draft-ietf-tokbind-https-01.txt   draft-ietf-tokbind-https-02.txt 
Internet Engineering Task Force A. Popov Internet Engineering Task Force A. Popov
Internet-Draft M. Nystroem Internet-Draft M. Nystroem
Intended status: Standards Track Microsoft Corp. Intended status: Standards Track Microsoft Corp.
Expires: January 1, 2016 D. Balfanz, Ed. Expires: April 17, 2016 D. Balfanz, Ed.
A. Langley A. Langley
Google Inc. Google Inc.
June 30, 2015 October 15, 2015
Token Binding over HTTP Token Binding over HTTP
draft-ietf-tokbind-https-01 draft-ietf-tokbind-https-02
Abstract Abstract
This document describes a collection of mechanisms that allow HTTP This document describes a collection of mechanisms that allow HTTP
servers to cryptographically bind authentication tokens (such as servers to cryptographically bind authentication tokens (such as
cookies and OAuth tokens) to a TLS [RFC5246] connection. cookies and OAuth tokens) to a TLS [RFC5246] connection.
We describe both _first-party_ as well as _federated_ scenarios. In We describe both _first-party_ as well as _federated_ scenarios. In
a first-party scenario, an HTTP server issues a security token (such a first-party scenario, an HTTP server issues a security token (such
as a cookie) to a client, and expects the client to send the security as a cookie) to a client, and expects the client to send the security
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
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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 January 1, 2016. This Internet-Draft will expire on April 17, 2016.
Copyright Notice Copyright Notice
Copyright (c) 2015 IETF Trust and the persons identified as the Copyright (c) 2015 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
2. The Sec-Token-Binding Header . . . . . . . . . . . . . . . . 3 2. The Token-Binding Header . . . . . . . . . . . . . . . . . . 3
3. Federation Use Cases . . . . . . . . . . . . . . . . . . . . 4 3. Federation Use Cases . . . . . . . . . . . . . . . . . . . . 4
3.1. Introduction . . . . . . . . . . . . . . . . . . . . . . 4 3.1. Introduction . . . . . . . . . . . . . . . . . . . . . . 4
3.2. Overview . . . . . . . . . . . . . . . . . . . . . . . . 4 3.2. Overview . . . . . . . . . . . . . . . . . . . . . . . . 4
3.3. HTTP Redirects . . . . . . . . . . . . . . . . . . . . . 6 3.3. HTTP Redirects . . . . . . . . . . . . . . . . . . . . . 6
3.4. Negotiated Key Parameters . . . . . . . . . . . . . . . . 6 3.4. Negotiated Key Parameters . . . . . . . . . . . . . . . . 7
4. Security Considerations . . . . . . . . . . . . . . . . . . . 7 4. Security Considerations . . . . . . . . . . . . . . . . . . . 7
4.1. Security Token Replay . . . . . . . . . . . . . . . . . . 7 4.1. Security Token Replay . . . . . . . . . . . . . . . . . . 7
4.2. Privacy Considerations . . . . . . . . . . . . . . . . . 7 4.2. Privacy Considerations . . . . . . . . . . . . . . . . . 7
4.3. Triple Handshake Vulnerability in TLS . . . . . . . . . . 7 4.3. Triple Handshake Vulnerability in TLS . . . . . . . . . . 7
5. References . . . . . . . . . . . . . . . . . . . . . . . . . 8 4.4. Sensitivity of the Token-Binding Header . . . . . . . . . 8
5.1. Normative References . . . . . . . . . . . . . . . . . . 8 4.5. Securing Federated Sign-On Protocols . . . . . . . . . . 9
5.2. Informative References . . . . . . . . . . . . . . . . . 8 5. References . . . . . . . . . . . . . . . . . . . . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9 5.1. Normative References . . . . . . . . . . . . . . . . . . 11
5.2. Informative References . . . . . . . . . . . . . . . . . 12
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12
1. Introduction 1. Introduction
The Token Binding Protocol [TBPROTO] defines a Token Binding ID for a The Token Binding Protocol [TBPROTO] defines a Token Binding ID for a
TLS connection between a client and a server. The Token Binding ID TLS connection between a client and a server. The Token Binding ID
of a TLS connection is related to a private key that the client of a TLS connection is related to a private key that the client
proves possession of to the server, and is long-lived (i.e., proves possession of to the server, and is long-lived (i.e.,
subsequent TLS connections between the same client and server have subsequent TLS connections between the same client and server have
the same Token Binding ID). When issuing a security token (e.g. an the same Token Binding ID). When issuing a security token (e.g. an
HTTP cookie or an OAuth token) to a client, the server can include HTTP cookie or an OAuth token) to a client, the server can include
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Token Binding ID that the client is using with a _different_ server Token Binding ID that the client is using with a _different_ server
than the one that the TokenBindingMessage is sent to. This is useful than the one that the TokenBindingMessage is sent to. This is useful
in federation scenarios. in federation scenarios.
1.1. Requirements Language 1.1. Requirements Language
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].
2. The Sec-Token-Binding Header 2. The Token-Binding Header
Once a client and server have negotiated the Token Binding Protocol Once a client and server have negotiated the Token Binding Protocol
with HTTP/1.1 or HTTP/2 (see The Token Binding Protocol [TBPROTO]), with HTTP/1.1 or HTTP/2 (see The Token Binding Protocol [TBPROTO]),
clients MUST include the Sec-Token-Binding header in their HTTP clients MUST include the Token-Binding header in their HTTP requests.
requests. The ABNF of the Sec-Token-Binding header is: The ABNF of the Token-Binding header is:
Sec-Token-Binding = "Sec-Token-Binding" ":" [CFWS] EncodedTokenBindingMessage Token-Binding = "Token-Binding" ":" [CFWS] EncodedTokenBindingMessage
The EncodedTokenBindingMessage is a web-safe Base64-encoding of the The EncodedTokenBindingMessage is a web-safe Base64-encoding of the
TokenBindingMessage as defined in the TokenBindingProtocol [TBPROTO]. TokenBindingMessage as defined in the TokenBindingProtocol [TBPROTO].
The TokenBindingMessage MUST contain a TokenBinding with The TokenBindingMessage MUST contain a TokenBinding with
TokenBindingType provided_token_binding, which MUST be signed with TokenBindingType provided_token_binding, which MUST be signed with
the Token Binding key used by the client for connections between the Token Binding key used by the client for connections between
itself and the server that the HTTP request is sent to (clients use itself and the server that the HTTP request is sent to (clients use
different Token Binding keys for different servers). The Token different Token Binding keys for different servers). The Token
Binding ID established by this TokenBinding is called a _Provided Binding ID established by this TokenBinding is called a _Provided
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that token to the TLS connection between the client and a Relying that token to the TLS connection between the client and a Relying
Party. Party.
In this section we describe mechanisms to achieve this. The common In this section we describe mechanisms to achieve this. The common
idea among these mechanisms is that a server (called the _Token idea among these mechanisms is that a server (called the _Token
Consumer_ in this document) gives the client permission to reveal the Consumer_ in this document) gives the client permission to reveal the
Provided Token Binding ID that is used between the client and itself, Provided Token Binding ID that is used between the client and itself,
to another server (called the _Token Provider_ in this document). to another server (called the _Token Provider_ in this document).
Also common across the mechanisms is how the Token Binding ID is Also common across the mechanisms is how the Token Binding ID is
revealed to the Token Provider: The client uses the Token Binding revealed to the Token Provider: The client uses the Token Binding
Protocol [TBPROTO], and includes a TokenBinding structure in the Sec- Protocol [TBPROTO], and includes a TokenBinding structure in the
Token-Binding HTTP header defined above. What differs between the Token-Binding HTTP header defined above. What differs between the
various mechanisms is _how_ the Token Consumer grants the permission various mechanisms is _how_ the Token Consumer grants the permission
to reveal the Token Binding ID to the Token Provider. Below we to reveal the Token Binding ID to the Token Provider. Below we
specify one such mechanism, which is suitable for redirect-based specify one such mechanism, which is suitable for redirect-based
interactions between Token Consumers and Token Providers. interactions between Token Consumers and Token Providers.
3.2. Overview 3.2. Overview
In a Federated Sign-On protocol, an Identity Provider issues an In a Federated Sign-On protocol, an Identity Provider issues an
identity token to a client, which sends the identity token to a identity token to a client, which sends the identity token to a
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Include-Referer-Token-Binding-ID = "Include-Referer-Token-Binding-ID" ":" Include-Referer-Token-Binding-ID = "Include-Referer-Token-Binding-ID" ":"
[CFWS] %x74.72.75.65 ; "true", case-sensitive [CFWS] %x74.72.75.65 ; "true", case-sensitive
Including this response header signals to the client that it should Including this response header signals to the client that it should
reveal the Token Binding ID used between the client and the Token reveal the Token Binding ID used between the client and the Token
Consumer to the Token Provider. In the absence of this response Consumer to the Token Provider. In the absence of this response
header, the client will not disclose any information about the Token header, the client will not disclose any information about the Token
Binding used between the client and the Token Consumer to the Token Binding used between the client and the Token Consumer to the Token
Provider. Provider.
This header has only meaning if the HTTP status code is 302 or 301, This header has only meaning if the HTTP status code is 301, 302,
and MUST be ignored by the client for any other status codes. If the 303, 307 or 308, and MUST be ignored by the client for any other
client supports the Token Binding Protocol, and has negotiated the status codes. If the client supports the Token Binding Protocol, and
Token Binding Protocol with both the Token Consumer and the Token has negotiated the Token Binding Protocol with both the Token
Provider, it already sends the following header to the Token Provider Consumer and the Token Provider, it already sends the following
with each HTTP request (see above): header to the Token Provider with each HTTP request (see above):
Sec-Token-Binding: EncodedTokenBindingMessage Token-Binding: EncodedTokenBindingMessage
The TokenBindingMessage SHOULD contain a TokenBinding with The TokenBindingMessage SHOULD contain a TokenBinding with
TokenBindingType referred_token_binding. If included, this TokenBindingType referred_token_binding. If included, this
TokenBinding MUST be signed with the Token Binding key used by the TokenBinding MUST be signed with the Token Binding key used by the
client for connections between itself and the Token Consumer (more client for connections between itself and the Token Consumer (more
specifically, the web origin that issued the Include-Referer-Token- specifically, the web origin that issued the Include-Referer-Token-
Binding-ID response header). The Token Binding ID established by Binding-ID response header). The Token Binding ID established by
this TokenBinding is called a _Referred Token Binding ID_. this TokenBinding is called a _Referred Token Binding ID_.
As described above, the TokenBindingMessage MUST additionally contain As described above, the TokenBindingMessage MUST additionally contain
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The Token Binding protocol uses persistent, long-lived TLS Token The Token Binding protocol uses persistent, long-lived TLS Token
Binding IDs. To protect privacy, TLS Token Binding IDs are never Binding IDs. To protect privacy, TLS Token Binding IDs are never
transmitted in clear text and can be reset by the user at any time, transmitted in clear text and can be reset by the user at any time,
e.g. when clearing browser cookies. Unique Token Binding IDs MUST be e.g. when clearing browser cookies. Unique Token Binding IDs MUST be
generated for connections to different origins, so they cannot be generated for connections to different origins, so they cannot be
used by cooperating servers to link user identities. used by cooperating servers to link user identities.
4.3. Triple Handshake Vulnerability in TLS 4.3. Triple Handshake Vulnerability in TLS
The Token Binding protocol relies on the tls_unique value to The Token Binding protocol relies on the exported key material (EKM)
associate a TLS connection with a TLS Token Binding. The triple value [RFC5705] to associate a TLS connection with a TLS Token
handshake attack [TRIPLE-HS] is a known TLS protocol vulnerability Binding. The triple handshake attack [TRIPLE-HS] is a known TLS
allowing the attacker to synchronize tls_unique values between TLS protocol vulnerability allowing the attacker to synchronize keying
connections. The attacker can then successfully replay bound tokens. manterial between TLS connections. The attacker can then
For this reason, the Token Binding protocol MUST NOT be negotiated successfully replay bound tokens. For this reason, the Token Binding
unless the Extended Master Secret TLS extension protocol MUST NOT be negotiated unless the Extended Master Secret TLS
[I-D.ietf-tls-session-hash] has also been negotiated. extension [I-D.ietf-tls-session-hash] has also been negotiated.
4.4. Sensitivity of the Token-Binding Header
The purpose of the Token Binding protocol is to convince the server
that the client that initiated the TLS connection controls a certain
key pair. For the server to correctly draw this conclusion after
processing the Token-Binding header, certain secrecy and integrity
requirements must be met.
For example, the client's private Token Binding key must be kept
secret by the client. If the private key is not secret, then another
actor in the system could create a valid Token Binding header,
impersonating the client. This can render the main purpose of the
protocol - to bind bearer tokens to certain clients - moot: Consider,
for example, an attacker who obtained (perhaps through a network
intrusion) an authentication cookie that a client uses with a certain
server. Consider further that the server bound that cookie to the
client's Token Binding ID precisely to thwart cookie theft. If the
attacker were to come into possession of the client's private key, he
could then establish a TLS connection with the server and craft a
Token-Binding header that matches the binding present in the cookie,
thus successfully authenticating as the client, and gaining access to
the client's data at the server. The Token Binding protocol, in this
case, didn't successfully bind the cookie to the client.
Likewise, we need integrity protection of the Token-Binding header: A
client shouldn't be tricked into sending a Token-Binding header to a
server that contains Token Binding messages about key pairs that the
client doesn't control. Consider an attacker A that somehow has
knowledge of the exported keying material (EKM) for a TLS connection
between a client C and a server S. (While that is somewhat unlikely,
it's also not entirely out of the question, since the client might
not treat the EKM as a secret - after all, a pre-image-resistant hash
function has been applied to the TLS master secret, making it
impossible for someone knowing the EKM to recover the TLS master
secret. Such considerations might lead some clients to not treat the
EKM as a secret.) Such an attacker A could craft a Token-Binding
header with A's key pair over C's EKM. If the attacker could now
trick C to send such a header to S, it would appear to S as if C
controls a certain key pair when in fact it doesn't (the attacker A
controls the key pair).
If A has a pre-existing relationship with S (perhaps has an account
on S), it now appears to the server S as if A is connecting to it,
even though it is really C. (If the server S doesn't simply use
Token Binding keys to identify clients, but also uses bound
authentication cookies, then A would also have to trick C into
sending one of A's cookies to S, which it can do through a variety of
means - inserting cookies through Javascript APIs, setting cookies
through related-domain attacks, etc.) In other words, A tricked C
into logging into A's account on S. This could lead to a loss of
privacy for C, since A presumably has some other way to also access
the account, and can thus indirectly observe A's behavior (for
example, if S has a feature that lets account holders see their
activity history on S).
Therefore, we need to protect the integrity of the Token-Binding
header. One origin should not be able to set the Token-Binding
header (through a DOM API or otherwise) that the User Agent uses with
another origin.
4.5. Securing Federated Sign-On Protocols
As explained above, in a federated sign-in scenario a client will
prove possession of two different key pairs to a Token Provider: One
key pair is the "provided" Token Binding key pair (which the client
normally uses with the Token Provider), and the other is the
"referred" Token Binding key pair (which the client normally uses
with the Token Consumer). The Token Provider is expected to issue a
token that is bound to the referred Token Binding key.
Both proofs (that of the provided Token Binding key and that of the
referred Token Binding key) are necessary. To show this, consider
the following scenario:
o The client has an authentication token with the Token Provider
that is bound to the client's Token Binding key.
o The client wants to establish a secure (i.e., free of men-in-the-
middle) authenticated session with the Token Consumer, but hasn't
done so yet (in other words, we're about to run the federated
sign-on protocol).
o A man-in-the-middle is allowed to intercept the connection between
client and Token Consumer or between Client and Token Provider (or
both).
The goal is to detect the presence of the man-in-the-middle in these
scenarios.
First, consider a man-in-the-middle between the client and the Token
Provider. Recall that we assume that the client possesses a bound
authentication token (e.g., cookie) for the Token Provider. The man-
in-the-middle can intercept and modify any message sent by the client
to the Token Provider, and any message sent by the Token Provider to
the client. (This means, among other things, that the man-in-the-
middle controls the Javascript running at the client in the origin of
the Token Provider.) It is not, however, in possession of the
client's Token Binding key. Therefore, it can either choose to
replace the Token Binding key in requests from the client to the
Token Provider, and create a Token-Binding header that matches the
TLS connection between the man-in-the-middle and the Token Provider;
or it can choose to leave the Token-Binding header unchanged. If it
chooses the latter, the signature in the Token Binding message
(created by the original client on the exported keying material (EKM)
for the connection between client and man-in-the-middle) will not
match the EKM between man-in-the-middle and the Token Provider. If
it chooses the former (and creates its own signature, with its own
Token Binding key, over the EKM for the connection between man-in-
the-middle and Token Provider), then the Token Binding message will
match the connection between man-in-the-middle and Token Provider,
but the Token Binding key in the message will not match the Token
Binding key that the client's authentication token is bound to.
Either way, the man-in-the-middle is detected by the Token Provider,
but only if the proof of key possession of the provided Token Binding
key is required in the protocol (as we do above).
Next, consider the presence of a man-in-the-middle between client and
Token Consumer. That man-in-the-middle can intercept and modify any
message sent by the client to the Token Consumer, and any message
sent by the Token Consumer to the client. The Token Consumer is the
party that redirects the client to the Token Provider. In this case,
the man-in-the-middle controls the redirect URL, and can tamper with
any redirect URL issued by the Token Consumer (as well as with any
Javascript running in the origin of the Token Consumer). The goal of
the man-in-the-middle is to trick the Token Issuer to issue a token
bound to _its_ Token Binding key, not to the Token Binding key of the
legitimate client. To thwart this goal of the man-in-the-middle, the
client's referred Token Binding key must be communicated to the Token
Producer in a manner that can not be affected by the man-in-the-
middle (who, as we recall, can modify redirect URLs and Javascript at
the client). Including the referred Token Binding message in the
Token-Binding header (as opposed to, say, including the referred
Token Binding key in an application-level message as part of the
redirect URL) is one way to assure that the man-in-the-middle between
client and Token Consumer cannot affect the communication of the
referred Token Binding key to the Token Provider.
Therefore, the Token-Binding header in the federated sign-on use case
contains both, a proof of possession of the provided Token Binding
key, as well as a proof of possession of the referred Token Binding
key.
5. References 5. References
5.1. Normative References 5.1. Normative References
[I-D.ietf-httpbis-header-compression] [I-D.ietf-httpbis-header-compression]
Peon, R. and H. Ruellan, "HPACK - Header Compression for Peon, R. and H. Ruellan, "HPACK - Header Compression for
HTTP/2", draft-ietf-httpbis-header-compression-12 (work in HTTP/2", draft-ietf-httpbis-header-compression-12 (work in
progress), February 2015. progress), February 2015.
[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, March 1997. Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/
RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC2616] Fielding, R., Gettys, J., Mogul, J., Frystyk, H., [RFC2616] Fielding, R., Gettys, J., Mogul, J., Frystyk, H.,
Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext
Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999. Transfer Protocol -- HTTP/1.1", RFC 2616, DOI 10.17487/
RFC2616, June 1999,
<http://www.rfc-editor.org/info/rfc2616>.
[RFC4492] Blake-Wilson, S., Bolyard, N., Gupta, V., Hawk, C., and B. [RFC4492] Blake-Wilson, S., Bolyard, N., Gupta, V., Hawk, C., and B.
Moeller, "Elliptic Curve Cryptography (ECC) Cipher Suites Moeller, "Elliptic Curve Cryptography (ECC) Cipher Suites
for Transport Layer Security (TLS)", RFC 4492, May 2006. for Transport Layer Security (TLS)", RFC 4492, DOI
10.17487/RFC4492, May 2006,
<http://www.rfc-editor.org/info/rfc4492>.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226, IANA Considerations Section in RFCs", BCP 26, RFC 5226,
May 2008. 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, August 2008. (TLS) Protocol Version 1.2", RFC 5246, DOI 10.17487/
RFC5246, August 2008,
<http://www.rfc-editor.org/info/rfc5246>.
[RFC5705] Rescorla, E., "Keying Material Exporters for Transport
Layer Security (TLS)", RFC 5705, DOI 10.17487/RFC5705,
March 2010, <http://www.rfc-editor.org/info/rfc5705>.
[RFC5929] Altman, J., Williams, N., and L. Zhu, "Channel Bindings [RFC5929] Altman, J., Williams, N., and L. Zhu, "Channel Bindings
for TLS", RFC 5929, July 2010. for TLS", RFC 5929, DOI 10.17487/RFC5929, July 2010,
<http://www.rfc-editor.org/info/rfc5929>.
[RFC7301] Friedl, S., Popov, A., Langley, A., and E. Stephan, [RFC7301] Friedl, S., Popov, A., Langley, A., and E. Stephan,
"Transport Layer Security (TLS) Application-Layer Protocol "Transport Layer Security (TLS) Application-Layer Protocol
Negotiation Extension", RFC 7301, July 2014. Negotiation Extension", RFC 7301, DOI 10.17487/RFC7301,
July 2014, <http://www.rfc-editor.org/info/rfc7301>.
[TBPROTO] Popov, A., "The Token Binding Protocol Version 1.0", 2014. [TBPROTO] Popov, A., "The Token Binding Protocol Version 1.0", 2014.
5.2. Informative References 5.2. Informative References
[I-D.ietf-httpbis-http2] [I-D.ietf-httpbis-http2]
Belshe, M., Peon, R., and M. Thomson, "Hypertext Transfer Belshe, M., Peon, R., and M. Thomson, "Hypertext Transfer
Protocol version 2", draft-ietf-httpbis-http2-17 (work in Protocol version 2", draft-ietf-httpbis-http2-17 (work in
progress), February 2015. progress), February 2015.
[I-D.ietf-tls-session-hash] [I-D.ietf-tls-session-hash]
Bhargavan, K., Delignat-Lavaud, A., Pironti, A., Langley, Bhargavan, K., Delignat-Lavaud, A., Pironti, A., Langley,
A., and M. Ray, "Transport Layer Security (TLS) Session A., and M. Ray, "Transport Layer Security (TLS) Session
Hash and Extended Master Secret Extension", draft-ietf- Hash and Extended Master Secret Extension", draft-ietf-
tls-session-hash-05 (work in progress), April 2015. tls-session-hash-06 (work in progress), July 2015.
[TRIPLE-HS] [TRIPLE-HS]
Bhargavan, K., Delignat-Lavaud, A., Fournet, C., Pironti, Bhargavan, K., Delignat-Lavaud, A., Fournet, C., Pironti,
A., and P. Strub, "Triple Handshakes and Cookie Cutters: A., and P. Strub, "Triple Handshakes and Cookie Cutters:
Breaking and Fixing Authentication over TLS. IEEE Breaking and Fixing Authentication over TLS. IEEE
Symposium on Security and Privacy", 2014. Symposium on Security and Privacy", 2014.
Authors' Addresses Authors' Addresses
Andrei Popov Andrei Popov
 End of changes. 22 change blocks. 
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