Internet DRAFT - draft-symeonidis-medup-requirements
draft-symeonidis-medup-requirements
Network Working Group I. Symeonidis
Internet-Draft University of Luxembourg
Intended status: Standards Track B. Hoeneisen
Expires: January 9, 2020 Ucom.ch
July 08, 2019
Privacy and Security Threat Analysis and Requirements for Private
Messaging
draft-symeonidis-medup-requirements-00
Abstract
[RFC8280] has identified and documented important principles, such as
Data Minimization, End-to-End, and Interoperability in order to
enable access to fundamental Human Rights. While (partial)
implementations of these concepts are already available, many current
applications lack Privacy support that the average user can easily
navigate. This document covers analysis of threats to privacy and
security and derives requirements from this threat analysis.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
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Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on January 9, 2020.
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to this document. Code Components extracted from this document must
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
1.2. Terms . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Motivation and Background . . . . . . . . . . . . . . . . . . 4
2.1. Objectives . . . . . . . . . . . . . . . . . . . . . . . 4
2.2. Known Implementations . . . . . . . . . . . . . . . . . . 4
2.2.1. Pretty Easy Privacy (pEp) . . . . . . . . . . . . . . 4
2.2.2. Autocrypt . . . . . . . . . . . . . . . . . . . . . . 6
2.3. Focus Areas (Design Challenges): . . . . . . . . . . . . 6
3. System Model . . . . . . . . . . . . . . . . . . . . . . . . 6
3.1. Entities . . . . . . . . . . . . . . . . . . . . . . . . 6
3.2. Basic Functional Requirements . . . . . . . . . . . . . . 7
4. Threat Analyses . . . . . . . . . . . . . . . . . . . . . . . 7
4.1. Adversarial model . . . . . . . . . . . . . . . . . . . . 7
4.2. Security Threats and Requirements . . . . . . . . . . . . 8
4.2.1. Spoofing and Entity Authentication . . . . . . . . . 8
4.2.2. Information Disclosure and Confidentiality . . . . . 8
4.2.3. Tampering With Data and Data Authentication . . . . . 8
4.2.4. Repudiation and Accountability (Non-Repudiation) . . 9
4.3. Privacy Threats and Requirements . . . . . . . . . . . . 9
4.3.1. Identifiability - Anonymity . . . . . . . . . . . . . 9
4.3.2. Linkability - Unlinkability . . . . . . . . . . . . . 10
4.3.3. Detectability and Observability - Undetectability . . 10
4.4. Information Disclosure - Confidentiality . . . . . . . . 10
4.5. Non-repudiation and Deniability . . . . . . . . . . . . . 10
5. Specific Security and Privacy Requirements . . . . . . . . . 11
5.1. Messages Exchange . . . . . . . . . . . . . . . . . . . . 11
5.1.1. Send Message . . . . . . . . . . . . . . . . . . . . 11
5.1.2. Receive Message . . . . . . . . . . . . . . . . . . . 11
5.2. Trust Management . . . . . . . . . . . . . . . . . . . . 12
5.3. Key Management . . . . . . . . . . . . . . . . . . . . . 12
5.4. Synchronization Management . . . . . . . . . . . . . . . 12
5.5. Identity Management . . . . . . . . . . . . . . . . . . . 13
5.6. User Interface . . . . . . . . . . . . . . . . . . . . . 13
6. Subcases . . . . . . . . . . . . . . . . . . . . . . . . . . 13
6.1. Interaction States . . . . . . . . . . . . . . . . . . . 13
6.2. Subcases for Sending Messages . . . . . . . . . . . . . . 14
6.3. Subcases for Receiving Messages . . . . . . . . . . . . . 15
7. Security Considerations . . . . . . . . . . . . . . . . . . . 15
8. Privacy Considerations . . . . . . . . . . . . . . . . . . . 16
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16
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10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 16
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 16
11.1. Normative References . . . . . . . . . . . . . . . . . . 16
11.2. Informative References . . . . . . . . . . . . . . . . . 16
Appendix A. Document Changelog . . . . . . . . . . . . . . . . . 18
Appendix B. Open Issues . . . . . . . . . . . . . . . . . . . . 18
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 18
1. Introduction
[RFC8280] has identified and documented important principles, such as
Data Minimization, End-to-End, and Interoperability in order to
enable access to fundamental Human Rights. While (partial)
implementations of these concepts are already available, many current
applications lack Privacy support that the average user can easily
navigate.
In MEDUP these issues are addressed based on Opportunistic Security
[RFC7435] principles.
This documents covers analysis of threats to privacy and security and
derives requirements from this threat analysis.
1.1. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
1.2. Terms
The following terms are defined for the scope of this document:
o Trustwords: A scalar-to-word representation of 16-bit numbers (0
to 65535) to natural language words. When doing a Handshake,
peers are shown combined Trustwords of both public keys involved
to ease the comparison. [I-D.birk-pep-trustwords]
o Trust On First Use (TOFU): cf. [RFC7435], which states: "In a
protocol, TOFU calls for accepting and storing a public key or
credential associated with an asserted identity, without
authenticating that assertion. Subsequent communication that is
authenticated using the cached key or credential is secure against
an MiTM attack, if such an attack did not succeed during the
vulnerable initial communication."
o Man-in-the-middle (MITM) attack: cf. [RFC4949], which states: "A
form of active wiretapping attack in which the attacker intercepts
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and selectively modifies communicated data to masquerade as one or
more of the entities involved in a communication association."
2. Motivation and Background
2.1. Objectives
o An open standard for secure messaging requirements
o Unified evaluation framework: unified goals and threat models
o Common pitfalls
o Future directions on requirements and technologies
o Misleading products on the wild (EFF secure messaging scorecard)
2.2. Known Implementations
2.2.1. Pretty Easy Privacy (pEp)
To achieve privacy of exchanged messages in an opportunistic way
[RFC7435], the following model (simplified) is proposed by pEp
(pretty Easy Privacy) [I-D.birk-pep]:
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----- -----
| A | | B |
----- -----
| |
+------------------------+ +------------------------+
| auto-generate key pair | | auto-generate key pair |
| (if no key yet) | | (if no key yet) |
+------------------------+ +------------------------+
| |
+-----------------------+ +-----------------------+
| Privacy Status for B: | | Privacy Status for A: |
| *Unencrypted* | | *Unencrypted* |
+-----------------------+ +-----------------------+
| |
| A sends message to B (Public Key |
| attached) / optionally signed, but |
| NOT ENCRYPTED |
+------------------------------------------>|
| |
| +-----------------------+
| | Privacy Status for A: |
| | *Encrypted* |
| +-----------------------+
| |
| B sends message to A (Public Key |
| attached) / signed and ENCRYPTED |
|<------------------------------------------+
| |
+-----------------------+ |
| Privacy Status for B: | |
| *Encrypted* | |
+-----------------------+ |
| |
| A and B successfully compare their |
| Trustwords over an alternative channel |
| (e.g., phone line) |
|<-- -- -- -- -- -- -- -- -- -- -- -- -- -->|
| |
+-----------------------+ +-----------------------+
| Privacy Status for B: | | Privacy Status for A: |
| *Trusted* | | *Trusted* |
+-----------------------+ +-----------------------+
| |
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pEp is intended to solve three problems :
o Key management
o Trust management
o Identity management
pEp is intended to be used in pre-existing messaging solutions and
provide Privacy by Default, at a minimum, for message content. In
addition, pEp provides technical data protection including metadata
protection.
An additional set of use cases applies to enterprise environments
only. In some instances, the enterprise may require access to
message content. Reasons for this may include the need to conform to
compliance requirements or virus/malware defense.
2.2.2. Autocrypt
Another known approach in this area is Autocrypt. Compared to pEp
(cf. Section 2.2.1) - there are certain differences, for example,
regarding the prioritization of support for legacy PGP [RFC4880]
implementations.
More information on Autocrypt can be found on: https://autocrypt.org/
background.html
[[ TODO: Input from autocrypt group ]]
2.3. Focus Areas (Design Challenges):
o Trust establishment: some human interaction
o Conversation security: no human interaction
o Transport privacy: no human interaction
3. System Model
3.1. Entities
o Users, sender and receiver(s): The communicating parties who
exchange messages, typically referred to as senders and receivers.
o Messaging operators and network nodes: The communicating service
providers and network nodes that are responsible for message
delivery and synchronization.
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o Third parties: Any other entity who interacts with the messaging
system.
3.2. Basic Functional Requirements
This section outlines the functional requirements. We follow the
requirements extracted from the literature on private emails and
instant messaging [Unger] [Ermoshina] [Clark].
o Message: send and receive message(s)
o Multi-device support: synchronization across multiple devices
o Group messaging: communication of more than 2 users
[[ TODO: Add more text on Group Messaging requirements. ]]
4. Threat Analyses
This section describes a set of possible threats. Note that not all
threats can be addressed, due to conflicting requirements.
4.1. Adversarial model
An adversary is any entity who leverages threats against the
communication system, whose goal is to gain improper access to the
message content and users' information. They can be anyone who is
involved in communication, such as users of the system, message
operators, network nodes, or even third parties.
o Internal - external: An adversary can seize control of entities
within the system, such as extracting information from a specific
entity or preventing a message from being sent. An external
adversary can only compromise the communication channels
themselves, eavesdropping and tampering with messaging such as
performing Man-in-the-Middle (MitM) attacks.
o Local - global: A local adversary can control one entity that is
part of a system, while a global adversary can seize control of
several entities in a system. A global adversary can also monitor
and control several parts of the network, granting them the
ability to correlate network traffic, which is crucial in
performing timing attacks.
o Passive - active: A passive attacker can only eavesdrop and
extract information, while an active attacker can tamper with the
messages themselves, such as adding, removing, or even modifying
them.
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Attackers can combine these adversarial properties in a number of
ways, increasing the effectiveness - and probable success - of their
attacks. For instance, an external global passive attacker can
monitor multiple channels of a system, while an internal local active
adversary can tamper with the messages of a targeted messaging
provider [Diaz].
4.2. Security Threats and Requirements
4.2.1. Spoofing and Entity Authentication
Spoofing occurs when an adversary gains improper access to the system
upon successfully impersonating the profile of a valid user. The
adversary may also attempt to send or receive messages on behalf of
that user. The threat posed by an adversary's spoofing capabilities
is typically based on the local control of one entity or a set of
entities, with each compromised account typically is used to
communicate with different end-users. In order to mitigate spoofing
threats, it is essential to have entity authentication mechanisms in
place that will verify that a user is the legitimate owner of a
messaging service account. The entity authentication mechanisms
typically rely on the information or physical traits that only the
valid user should know/possess, such as passwords, valid public keys,
or biometric data like fingerprints.
4.2.2. Information Disclosure and Confidentiality
An adversary aims to eavesdrop and disclose information about the
content of a message. They can attempt to perform a man-in-the-
middle attack (MitM). For example, an adversary can attempt to
position themselves between two communicating parties, such as
gaining access to the messaging server and remain undetectable while
collecting information transmitted between the intended users. The
threat posed by an adversary can be from local gaining control of one
point of a communication channel such as an entity or a communication
link within the network. The adversarial threat can also be broader
in scope, such as seizing global control of several entities and
communication links within the channel. That grants the adversary
the ability to correlate and control traffic in order to execute
timing attacks, even in the end-to-end communication systems [Tor].
Therefore, confidentiality of messages exchanged within a system
should be guaranteed with the use of encryption schemes
4.2.3. Tampering With Data and Data Authentication
An adversary can also modify the information stored and exchanged
between the communication entities in the system. For instance, an
adversary may attempt to alter an email or an instant message by
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changing the content of them. As a result, it can be anyone but the
users who are communicating, such as the message operators, the
network node, or third parties. The threat posed by an adversary can
be in gaining local control of an entity which can alter messages,
usually resulting in a MitM attack on an encrypted channel.
Therefore, no honest party should accept a message that was modified
in transit. Data authentication of messages exchanged needs to be
guaranteed, such as with the use of Message Authentication Code (MAC)
and digital signatures.
4.2.4. Repudiation and Accountability (Non-Repudiation)
Adversaries can repudiate, or deny, the status of the message to
users of the system. For instance, an adversary may attempt to
provide inaccurate information about an action performed, such as
about sending or receiving an email. An adversary can be anyone who
is involved in communicating, such as the users of the system, the
message operators, and the network nodes. To mitigate repudiation
threats, accountability, and non-repudiation of actions performed
must be guaranteed. Non-repudiation of action can include proof of
origin, submission, delivery, and receipt between the intended users.
Non-repudiation can be achieved with the use of cryptographic schemes
such as digital signatures and audit trails such as timestamps.
4.3. Privacy Threats and Requirements
4.3.1. Identifiability - Anonymity
Identifiability is defined as the extent to which a specific user can
be identified from a set of users, which is the identifiability set.
Identification is the process of linking information to allow the
inference of a particular user's identity [RFC6973]. An adversary
can identify a specific user associated with Items of Interest (IOI),
which include items such as the ID of a subject, a sent message, or
an action performed. For instance, an adversary may identify the
sender of a message by examining the headers of a message exchanged
within a system. To mitigate identifiability threats, the anonymity
of users must be guaranteed. Anonymity is defined from the attackers
perspective as the "the attacker cannot sufficiently identify the
subject within a set of subjects, the anonymity set" [Pfitzmann].
Essentially, in order to make anonymity possible, there always needs
to be a set of possible users such that for an adversary the
communicating user is equally likely to be of any other user in the
set [Diaz]. Thus, an adversary cannot identify who is the sender of
a message. Anonymity can be achieved with the use of pseudonyms and
cryptographic schemes such as anonymous remailers (i.e., mixnets),
anonymous communications channels (e.g., Tor), and secret sharing.
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4.3.2. Linkability - Unlinkability
Linkability occurs when an adversary can sufficiently distinguish
within a given system that two or more IOIs such as subjects (i.e.,
users), objects (i.e., messages), or actions are related to each
other [Pfitzmann]. For instance, an adversary may be able to relate
pseudonyms by analyzing exchanged messages and deduce that the
pseudonyms belong to one user (though the user may not necessarily be
identified in this process). Therefore, unlinkability of IOIs should
be guaranteed through the use of pseudonyms as well as cryptographic
schemes such as anonymous credentials.
4.3.3. Detectability and Observability - Undetectability
Detectability occurs when an adversary is able to sufficiently
distinguish an IOI, such as messages exchanged within the system,
from random noise [Pfitzmann]. Observability occurs when that
detectability occurs along with a loss of anonymity for the entities
within that same system. An adversary can exploit these states in
order to infer linkability and possibly identification of users
within a system. Therefore, undetectability of IOIs should be
guaranteed, which also ensures unobservability. Undetectability for
an IOI is defined as that "the attacker cannot sufficiently
distinguish whether it exists or not." [Pfitzmann]. Undetectability
can be achieved through the use of cryptographic schemes such as mix-
nets and obfuscation mechanisms such as the insertion of dummy
traffic within a system.
4.4. Information Disclosure - Confidentiality
Information disclosure - or loss of confidentiality - about users,
message content, metadata or other information is not only a security
but also a privacy threat that a communicating system can face. For
example, a successful MitM attack can yield metadata that can be used
to determine with whom a specific user communicates with, and how
frequently. To guarantee the confidentiality of messages and prevent
information disclosure, security measures need to be guaranteed with
the use of cryptographic schemes such as symmetric, asymmetric or
homomorphic encryption and secret sharing.
4.5. Non-repudiation and Deniability
Non-repudiation can be a threat to a user's privacy for private
messaging systems, in contrast to security. As discussed in section
6.1.4, non-repudiation should be guaranteed for users. However, non-
repudiation carries a potential threat vector in itself when it is
used against a user in certain instances. For example, whistle-
blowers may find non-repudiation used against them by adversaries,
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particularly in countries with strict censorship policies and in
cases where human lives are at stake. Adversaries in these
situations may seek to use shreds of evidence collected within a
communication system to prove to others that a whistle-blowing user
was the originator of a specific message. Therefore, plausible
deniability is essential for these users, to ensure that an adversary
can neither confirm nor contradict that a specific user sent a
particular message. Deniability can be guaranteed through the use of
cryptographic protocols such as off-the-record messaging.
[[ TODO: Describe relation of the above introduced Problem Areas to
scope of MEDUP ]]
5. Specific Security and Privacy Requirements
[[ This section is still in early draft state, to be substantially
improved in future revisions. Among other things, there needs to be
clearer distinction between MEDUP requirements, and those of a
specific implementation. ]]
5.1. Messages Exchange
5.1.1. Send Message
o Send encrypted and signed message to another peer
o Send unencrypted and unsigned message to another peer
Note: Subcases of sending messages are outlined in Section 6.2.
5.1.2. Receive Message
o Receive encrypted and signed message from another peer
o Receive encrypted, but unsigned message from another peer
o Receive signed, but unencrypted message from another peer
o Receive unencrypted and unsigned message from another peer
Note: Subcases of receiving messages are outlined in Section 6.3.
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5.2. Trust Management
o Trust rating of a peer is updated (locally) when:
* Public Key is received the first time
* Trustwords have been compared successfully and confirmed by
user (see above)
* Trust of a peer is revoked (cf. Section 5.3, Key Reset)
o Trust of a public key is synchronized among different devices of
the same user
Note: Synchronization management (such as the establishment or
revocation of trust) among a user's own devices is described in
Section 5.4
5.3. Key Management
o New Key pair is automatically generated at startup if none are
found.
o Public Key is sent to peer via message attachment
o Once received, Public Key is stored locally
o Key pair is declared invalid and other peers are informed (Key
Reset)
o Public Key is marked invalid after receiving a key reset message
o Public Keys of peers are synchronized among a user's devices
o Private Keys are synchronized among a user's devices
Note: Synchronization management (such as establish or revoke
trust) among a user's own devices is described in Section 5.4
5.4. Synchronization Management
A device group is comprised of devices belonging to one user, which
share the same key pairs in order to synchronize data among them. In
a device group, devices of the same user mutually grant
authentication.
o Form a device group of two (yet ungrouped) devices of the same
user
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o Add another device of the same user to existing device group
o Leave device group
o Remove other device from device group
5.5. Identity Management
o All involved parties share the same identity system
5.6. User Interface
[[ TODO ]]
6. Subcases
6.1. Interaction States
The basic model consists of different interaction states:
1. Both peers have no public key of each other, no trust possible
2. Only one peer has the public key of the other peer, but no trust
3. Only one peer has the public key of the other peer and trusts
that public key
4. Both peers have the public key of each other, but no trust
5. Both peers have exchanged public keys, but only one peer trusts
the other peer's public key
6. Both peers have exchanged public keys, and both peers trust the
other's public key
The following table shows the different interaction states possible:
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+-------+-----------------+-------------------+---------+-----------+
| state | Peer's Public | My Public Key | Peer | Peer |
| | Key available | available to Peer | Trusted | trusts me |
+-------+-----------------+-------------------+---------+-----------+
| 1. | no | no | N/A | N/A |
| | | | | |
| 2a. | no | yes | N/A | no |
| | | | | |
| 2b. | yes | no | no | N/A |
| | | | | |
| 3a. | no | yes | N/A | yes |
| | | | | |
| 3b. | yes | no | yes | N/A |
| | | | | |
| 4. | yes | yes | no | no |
| | | | | |
| 5a. | yes | yes | no | yes |
| | | | | |
| 5b. | yes | yes | yes | no |
| | | | | |
| 6. | yes | yes | yes | yes |
+-------+-----------------+-------------------+---------+-----------+
In the simplified model, only interaction states 1, 2, 4 and 6 are
depicted. States 3 and 5 may result from e.g. key mistrust or
abnormal user behavior. Interaction states 1, 2 and 4 are part of
TOFU. For a better understanding, you may consult the figure in
Section 2.2.1 above.
Note: In situations where one peer has multiple key pairs, or group
conversations are occurring, interaction states become increasingly
complex. For now, we will focus on a single bilateral interaction
between two peers, each possessing a single key pair.
[[ Note: Future versions of this document will address more complex
cases ]]
6.2. Subcases for Sending Messages
o If peer's Public Key not available (Interaction States 1, 2a, and
3a)
* Send message Unencrypted (and unsigned)
o If peer's Public Key available (Interaction States 2b, 3b, 4, 5a,
5b, 6)
* Send message Encrypted and Signed
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6.3. Subcases for Receiving Messages
o If peer's Public Key not available (Interaction States 1, 2a, and
3a)
* If message is signed
+ ignore signature
* If message is encrypted
+ decrypt with caution
* If message unencrypted
+ No further processing regarding encryption
o If peer's Public Key available or can be retrieved from received
message (Interaction States 2b, 3b, 4, 5a, 5b, 6)
* If message is signed
+ verify signature
+ If message is encrypted
- Decrypt
+ If message unencrypted
- No further processing regarding encryption
* If message unsigned
+ If message is encrypted
- exception
+ If message unencrypted
- No further processing regarding encryption
7. Security Considerations
Relevant security considerations are outlined in Section 4.2.
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8. Privacy Considerations
Relevant privacy considerations are outlined in Section 4.3.
9. IANA Considerations
This document requests no action from IANA.
[[ RFC Editor: This section may be removed before publication. ]]
10. Acknowledgments
The authors would like to thank the following people who have
provided feedback or significant contributions to the development of
this document: Athena Schumacher, Claudio Luck, Hernani Marques,
Kelly Bristol, Krista Bennett, and Nana Karlstetter.
11. References
11.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC4949] Shirey, R., "Internet Security Glossary, Version 2",
FYI 36, RFC 4949, DOI 10.17487/RFC4949, August 2007,
<https://www.rfc-editor.org/info/rfc4949>.
[RFC7435] Dukhovni, V., "Opportunistic Security: Some Protection
Most of the Time", RFC 7435, DOI 10.17487/RFC7435,
December 2014, <https://www.rfc-editor.org/info/rfc7435>.
11.2. Informative References
[Clark] Clark, J., van Oorschot, P., Ruoti, S., Seamons, K., and
D. Zappala, "Securing Email", CoRR abs/1804.07706, 2018.
[Diaz] Diaz, C., Seys, St., Claessens, J., and B. Preneel,
"Towards Measuring Anonymity", PET Privacy Enhancing
Technologies, Second International Workshop, San
Francisco, CA, USA, April 14-15, 2002, Revised Papers, pp.
54-68, 2002.
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[Ermoshina]
Ermoshina, K., Musiani, F., and H. Halpin, "End-to-End
Encrypted Messaging Protocols: An Overview", INSCI 2016:
pp. 244-254, 2016.
[I-D.birk-pep]
Marques, H. and B. Hoeneisen, "pretty Easy privacy (pEp):
Privacy by Default", draft-birk-pep-03 (work in progress),
March 2019.
[I-D.birk-pep-trustwords]
Birk, V., Marques, H., and B. Hoeneisen, "IANA
Registration of Trustword Lists: Guide, Template and IANA
Considerations", draft-birk-pep-trustwords-03 (work in
progress), March 2019.
[Pfitzmann]
Pfitzmann, A. and M. Hansen, "A terminology for talking
about privacy by data minimization: Anonymity,
unlinkability, undetectability, unobservability,
pseudonymity, and identity management", 2010,
<https://nyuscholars.nyu.edu/en/publications/
sok-secure-messaging>.
[RFC4880] Callas, J., Donnerhacke, L., Finney, H., Shaw, D., and R.
Thayer, "OpenPGP Message Format", RFC 4880,
DOI 10.17487/RFC4880, November 2007,
<https://www.rfc-editor.org/info/rfc4880>.
[RFC6973] Cooper, A., Tschofenig, H., Aboba, B., Peterson, J.,
Morris, J., Hansen, M., and R. Smith, "Privacy
Considerations for Internet Protocols", RFC 6973,
DOI 10.17487/RFC6973, July 2013,
<https://www.rfc-editor.org/info/rfc6973>.
[RFC8280] ten Oever, N. and C. Cath, "Research into Human Rights
Protocol Considerations", RFC 8280, DOI 10.17487/RFC8280,
October 2017, <https://www.rfc-editor.org/info/rfc8280>.
[Tor] Project, T., "One cell is enough to break Tor's
anonymity", June 2019, <https://blog.torproject.org/
one-cell-enough-break-tors-anonymity/>.
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[Unger] Unger, N., Dechand, S., Bonneau, J., Fahl, S., Perl, H.,
Goldberg, I., and M. Smith, "SoK: Secure Messaging",
IEEE Proceedings - 2015 IEEE Symposium on Security and
Privacy, SP 2015, pages 232-249, July 2015,
<https://nyuscholars.nyu.edu/en/publications/
sok-secure-messaging>.
Appendix A. Document Changelog
[[ RFC Editor: This section is to be removed before publication ]]
o draft-symeonidis-medup-requirements-00:
* Initial version
Appendix B. Open Issues
[[ RFC Editor: This section should be empty and is to be removed
before publication ]]
o Add references to used materials (in particular threat analyses
part)
o Get content from Autocrypt (Section 2.2.2)
o Add more text on Group Messaging requirements
o Decide on whether or not "enterprise requirement" will go to this
document
Authors' Addresses
Iraklis Symeonidis
University of Luxembourg
29, avenue JF Kennedy
L-1855 Luxembourg
Luxembourg
Email: iraklis.symeonidis@uni.lu
URI: https://wwwen.uni.lu/snt/people/iraklis_symeonidis
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Bernie Hoeneisen
Ucom Standards Track Solutions GmbH
CH-8046 Zuerich
Switzerland
Phone: +41 44 500 52 40
Email: bernie@ietf.hoeneisen.ch (bernhard.hoeneisen AT ucom.ch)
URI: https://ucom.ch/
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