IEC TR 62351-90-2:2018
(Main)Power systems management and associated information exchange - Data and communications security - Part 90-2: Deep packet inspection of encrypted communications
Power systems management and associated information exchange - Data and communications security - Part 90-2: Deep packet inspection of encrypted communications
IEC TR 62351-90-2:2018, which is a technical report, addresses the need to perform Deep Packet Inspection (DPI) on communication channels secured by IEC 62351. The main focus is the illustration of the state-of-the art of DPI techniques that can be applied to the various kinds of channels, highlighting the possible security risks and implementation costs. Additional, beyond state-of-the-art proposals are also described in order to circumvent the main limits of existing solutions.
It is to be noted that some communications secured by IEC 62351 are not encrypted, but only add integrity and non-repudiation of the message – however they are mentioned here for the sake of completeness around IEC 62351 and DPI
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IEC TR 62351-90-2
Edition 1.0 2018-09
TECHNICAL
REPORT
colour
inside
Power systems management and associated information exchange – Data and
communications security –
Part 90-2: Deep packet inspection of encrypted communications
IEC TR 62351-90-2:2018-09(en)
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IEC TR 62351-90-2
Edition 1.0 2018-09
TECHNICAL
REPORT
colour
inside
Power systems management and associated information exchange – Data and
communications security –
Part 90-2: Deep packet inspection of encrypted communications
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 33.200 ISBN 978-2-8322-6038-8
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® Registered trademark of the International Electrotechnical Commission---------------------- Page: 3 ----------------------
– 2 – IEC TR 62351-90-2:2018 IEC 2018
CONTENTS
FOREWORD ........................................................................................................................... 4
INTRODUCTION ..................................................................................................................... 6
1 Scope .............................................................................................................................. 7
2 Normative references ...................................................................................................... 7
3 Terms, definitions and abbreviated terms ........................................................................ 8
3.1 Terms and definitions .............................................................................................. 8
3.2 Abbreviated terms ................................................................................................... 8
4 Overview ......................................................................................................................... 8
5 Monitoring and auditing requirements .............................................................................. 9
5.1 Use cases from utilities ........................................................................................... 9
5.2 Use cases from vendors.......................................................................................... 9
5.3 A similar use case: Encrypted SIP Calls Recording ............................................... 10
6 Overview of encrypted channels in IEC 62351 ............................................................... 10
6.1 General ................................................................................................................. 10
6.2 IEC 62351-3 ......................................................................................................... 10
6.3 IEC TS 62351-4 .................................................................................................... 10
6.4 IEC TS 62351-6 .................................................................................................... 11
7 DPI for encrypted communication techniques evaluation framework .............................. 11
8 State of the art of ready techniques ............................................................................... 12
8.1 General ................................................................................................................. 12
8.2 Unencrypted TLS .................................................................................................. 12
8.3 Private key sharing ............................................................................................... 13
9 State of the art of techniques that need adaptation ........................................................ 14
9.1 General ................................................................................................................. 14
9.2 Proxy .................................................................................................................... 14
9.3 Advanced Middlebox (mcTLS) ............................................................................... 16
9.4 Secure session-key sharing .................................................................................. 18
9.5 Delayed secure session-key sharing ..................................................................... 20
9.6 Application-level mirroring ..................................................................................... 21
10 Additional proposals ...................................................................................................... 23
10.1 Secure private-key sharing ................................................................................... 23
11 State of the art summary ............................................................................................... 24
12 Practical considerations for ready techniques ................................................................ 26
12.1 General ................................................................................................................. 26
12.2 Unencrypted TLS .................................................................................................. 26
12.3 Private-key sharing ............................................................................................... 26
12.4 Recommendations to mitigate risks ....................................................................... 26
13 Future challenges .......................................................................................................... 27
Bibliography .......................................................................................................................... 28
Figure 1 – Unencrypted TLS sample architecture .................................................................. 12
Figure 2 – Private Key sharing sample architecture .............................................................. 13
Figure 3 – Proxy scenario sample architecture ...................................................................... 15
Figure 4 – Advanced Middlebox sample architecture ............................................................. 17
---------------------- Page: 4 ----------------------IEC TR 62351-90-2:2018 IEC 2018 – 3 –
Figure 5 – Secure session-key sharing sample architecture .................................................. 18
Figure 6 – Delayed secure session-sharing sample architecture ........................................... 20
Figure 7 – Application-level mirroring sample architecture .................................................... 22
Table 1 – State of the art summary ....................................................................................... 25
---------------------- Page: 5 ----------------------– 4 – IEC TR 62351-90-2:2018 IEC 2018
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
POWER SYSTEMS MANAGEMENT
AND ASSOCIATED INFORMATION EXCHANGE –
DATA AND COMMUNICATIONS SECURITY –
Part 90-2: Deep packet inspection
of encrypted communications
FOREWORD
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The main task of IEC technical committees is to prepare International Standards. However, a
technical committee may propose the publication of a technical report when it has collected
data of a different kind from that which is normally published as an International Standard, for
example "state of the art".IEC TR 62351-90-2, which is a technical report, has been prepared by IEC technical
committee 57: Power systems management and associated information exchange.---------------------- Page: 6 ----------------------
IEC TR 62351-90-2:2018 IEC 2018 – 5 –
The text of this Technical Report is based on the following documents:
Enquiry draft Report on voting
57/1939/DTR 57/2002/RVDTR
Full information on the voting for the approval of this technical report can be found in the
report on voting indicated in the above table.This document has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all parts in the IEC 62351 series, published under the general title Power systems
management and associated information exchange – Data and communications security, can
be found on the IEC website.The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under "http://webstore.iec.ch" in the data related to
the specific document. At this date, the document will be• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
A bilingual version of this publication may be issued at a later date.
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colour printer.---------------------- Page: 7 ----------------------
– 6 – IEC TR 62351-90-2:2018 IEC 2018
INTRODUCTION
This part of IEC 62351, which is a technical report, analyses the impact of encrypted
communication channels in power systems introduced with the IEC 62351 series. As defined
in IEC 62351 an encrypted channel can be employed when communicating with IEDs and
encryption can be adopted at message level as well. For example, the use of encrypting TLS
setups according to IEC 62351-3 introduces some difficulties when Deep Packet Inspection
(DPI) is needed to inspect the communication channel for monitoring, auditing and validation
needs.In this document different techniques are analyzed that can be employed to circumvent these
issues when DPI of communications is required.---------------------- Page: 8 ----------------------
IEC TR 62351-90-2:2018 IEC 2018 – 7 –
POWER SYSTEMS MANAGEMENT
AND ASSOCIATED INFORMATION EXCHANGE –
DATA AND COMMUNICATIONS SECURITY –
Part 90-2: Deep packet inspection
of encrypted communications
1 Scope
This part of IEC 62351, which is a technical report, addresses the need to perform Deep
Packet Inspection (DPI) on communication channels secured by IEC 62351. The main focus is
the illustration of the state-of-the art of DPI techniques that can be applied to the various
kinds of channels, highlighting the possible security risks and implementation costs.
Additional, beyond state-of-the-art proposals are also described in order to circumvent the
main limits of existing solutions.It is to be noted that some communications secured by IEC 62351 are not encrypted, but only
add integrity and non-repudiation of the message – however they are mentioned here for the
sake of completeness around IEC 62351 and DPI.2 Normative references
The following documents are referred to in the text in such a way that some or all of their
content constitutes requirements of this document. For dated references, only the edition
cited applies. For undated references, the latest edition of the referenced document (including
any amendments) applies.IEC 62351-3, Power systems management and associated information exchange – Data and
communications security – Part 3: Communication network and system security – Profiles
including TCP/IPIEC TS 62351-4, Power systems management and associated information exchange – Data
and communications security – Part 4: Profiles including MMSIEC TS 62351-5, Power systems management and associated information exchange – Data
and communications security – Part 5: Security for IEC 60870-5 and derivativesIEC TS 62351-6, Power systems management and associated information exchange – Data
and communications security – Part 6: Security for IEC 61850IEC 62351-7, Power systems management and associated information exchange – Data and
communications security – Part 7: Network and System Management (NSM) data object
modelsIEC TS 62351-8, Power systems management and associated information exchange – Data
and communications security – Part 8: Role-based access control---------------------- Page: 9 ----------------------
– 8 – IEC TR 62351-90-2:2018 IEC 2018
3 Terms, definitions and abbreviated terms
3.1 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 62351-3,
IEC TS 62351-4 and IEC TS 62351-5 apply.ISO and IEC maintain terminological databases for use in standardization at the following
addresses:• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.2 Abbreviated terms
For the purposes of this document, the following abbreviated terms apply.
CA Certificate Authority
DPI Deep Packet Inspection
GDOI Group Domain of Interpretation
IED Intelligent Electronic Device
LDAP Lightweight Directory Access Protocol
TLS Transport Layer Security
PDU Protocol Data Unit
PFS Perfect Forward Secrecy
RBAC Role Based Access Control
SCADA Supervisory Control and Data Acquisition
SNMP Simple Network Management Protocol
4 Overview
DPI is a form of network communication analysis applied to every single bit of information
exchanged by nodes over the network. It is used for protocol validation, live virus checking,
and in general for intrusion detection or intrusion prevention purposes. DPI enables advanced
network monitoring and management but at the same time can enable for malicious intentions
as well (e.g. eavesdropping).Plaintext communications between nodes can be easily examined with DPI tools over their
route. Encrypted channels on the other hand require additional steps to enable DPI, for
instance:a) the sharing of the encryption key with the system performing DPI or
b) letting the communication flow into the DPI system be plaintext again.
Sharing some of the keying materials used for encryption with a DPI Probe will make the end
to end encryption less secure, and thus when adopting one approach or another it is important
to know advantages and disadvantages with respect to security impact, implementation costs
and performance impact.The driving factor behind this document is the need of a structured, standardized manner of
enabling DPI with encrypted channels, to eliminate the chance that unofficial, less secure
methods will be used.---------------------- Page: 10 ----------------------
IEC TR 62351-90-2:2018 IEC 2018 – 9 –
5 Monitoring and auditing requirements
5.1 Use cases from utilities
Ensuring reliable 24/7 operation of power systems requires:
1) The visibility of communication details, to validate correct behavior and troubleshoot
issues coming from software bugs, hardware malfunctions and/or network failures.2) The need to continuously validate that the given security requirements are always applied
and not bypassed, temporarily or permanently after the first acceptance tests of the
system.The need for deep monitoring of communication channels between IEDs and SCADA and/or
between IEDs by an independent device is basically driven by the same factors behind the
independent monitoring system required by IEC 62351-7. Leaving the system without an
independent monitoring device would expose its state to issues caused and hidden by the
system itself: these issues can be bugs, defects, software or hardware failures.This trusted device, namely a DPI Probe, is needed to inspect the communication channels in
a controlled and trusted manner.IEC 62351-7 defines a framework for proper monitoring of IEDs by employing a specific set of
status variables to be monitored through SNMP. Given the requirements detailed in this
section it should be clear that the current aim of IEC 62351-7 is quite different, as it enables
the provision of a synthesis of the status of IEDs and is not engineered to support the detailed
analysis of network packets sent and received on IEC 62351 channels.5.2 Use cases from vendors
Automation vendors implement and maintain the hardware and software equipment behind
utilities’ infrastructures. The need to monitor encrypted channels can be analyzed considering
the different communications happening in the system:1) Configuration communication between tool (client) and devices/IEDs (servers): when
encrypted, a TLS communication is often used to perform these tasks. Monitoring this kind
of communication can help to spot attacks trying to upload bad configuration data to the
IED.2) SV (Sample Values) going to or coming from external sources, integrity checked with
IEC TS 62351-6. Monitoring this communication can spot if fake data is being injected into
the network and used to alter the process.3) User authentication at GUIs/Applications/Tools: LDAP communication protected with TLS
(with Windows protocols or IEC TS 62351-8). It can be interesting to inspect these steps
to detect specific attacks to the authentication system.4) Applications/Tools Browser GUIs: HTTPS. Attacks targeting HTTP/HTTPS endpoints are
worth analyzing to prevent several kinds of issues on the server side.5) Patching: should be delivered via TLS. This is worth monitoring to help detect malicious
updates being delivered to IEDs or other system components.Even though advanced/proper application logging may be used by the vendor to detect and
notify security breaches in all the communications happening above, there is still a blind spot
left: improper or incomplete implementation of the system itself. Combining logging and
monitoring by a trusted DPI Probe allows the improvement of detection capabilities.
---------------------- Page: 11 ----------------------– 10 – IEC TR 62351-90-2:2018 IEC 2018
5.3 A similar use case: Encrypted SIP Calls Recording
A similar use case is reported and analyzed in the report of the IETF – SIPPING Working
Group 2008 [3] . In particular, in this scenario the communications of interest are VoIP calls
using the SIP protocol.Citing words in the IETF work, call recording is an important feature in enterprise telephony
applications. Some industries such as financial traders have requirements to record all calls in
which customers give trading orders. In others, calls are recorded, as the near ubiquitous
announcement says, “for training and quality control purposes”. Yet in others, all calls are not
recorded, and only statistical audits are done.This scenario does not use TLS but instead a bespoke encrypted variation of the plain RTP
protocol, named SRTP.Moreover, the system uses a scheme with a master key and session keys, thus without
mutual authentication.Although the SIP use case has some technical differences with the use case analyzed in this
document, it will be used throughout the document as a basis for technical solutions and
known issues.6 Overview of encrypted channels in IEC 62351
6.1 General
IEC 62351 defines encryption functionality in different parts of the standard. These are briefly
depicted in this clause. Note that although IEC 62351-3 defines encryption functionality by
defining specific cipher suites, it can only be used in conjunction with other parts such as 4, 5,
and 6.6.2 IEC 62351-3
IEC 62351-3 regulates the use of the TLS protocol. It narrows down the available options in
TLS by predefining a certain feature set or functionality to be used. This relates to cipher
suites, enabling encryption and also specific requirements to the TLS session management. It
is the foundation of several specific secure protocols, such as IEC TS 62351-4, IEC TS
62351-6, and IEC 60870-5-7 and is thus the base for transport level security. Besides the
narrowing of options, IEC 62351-3 also requires the referencing standard to define certain
other features and setting of TLS.6.3 IEC TS 62351-4
In IEC TS 62351-4, communication to IEDs can be secured with two main approaches:
1) T-Profile – transport level profile by means of TLS as described in IEC 62351-3. Note that
IEC TS 62351-4 defines a set of cipher suites to be supported mandatorily as well as
specific TLS session management settings. The negotiation of the encryption settings is
part of the TLS handshake, which is done at the setup time of a TLS session or as part of
the session management, when reconnecting or updating the session key. The negotiated
session key is direction specific and applied on a per message base.2) A-Profile – application profiles define different cryptographic protection on application
level. Specifically, the A+-Profile and the AE+-Profile are defined. In the context of
encryption, only the AE+-Profile provides the features for confidentiality protection. In the
AE+-Profile the key management is included in the profile definition and is performed also
___________Numbers in square brackets refer to the bibliography.
---------------------- Page: 12 ----------------------
IEC TR 62351-90-2:2018 IEC 2018 – 11 –
on application level. The negotiated key is used on a per message-level. The session key
may be updated during the established session by either side. The negotiated session key
is direction specific and applied on a per message base.These two approaches can also be used jointly. Note that in IEC TS 62351-4:2008, the A-
Profile did not provide encryption options.6.4 IEC TS 62351-6
In IEC TS 62351-6 the IEC 61850 communication channels are secured with different
approaches. GOOSE, GSE Management and Sampled Values channels use anauthentication, integrity and confidentiality security extension with group keys distributed
through GDOI. MMS communications are secured as specified in IEC TS 62351-4.7 DPI for encrypted communication techniques evaluation framework
Existing or possibly new DPI techniques will be evaluated according to security, performance
and costs criteria:Security
• Preserves End to End confidentiality: this criterion will be Yes if the communication
between devices is left “as-is”. It will be No if plaintext communication is restored at some
point.• IEC 62351 RBAC works: this criterion is a Yes/No result on whether the technique allows
the RBAC functionalities to work in a transparent manner.• Works without seeing handshake: this criterion is Yes if DPI can be performed without
having captured the entire handshake of the communication. This criterion has been
added because sometimes it’s interesting to start performing DPI even though thecommunication is already active, as re-initializing just for DPI purposes may impact the
systems under observation in an undesired manner.• Full third-party monitoring: this criterion is Yes if the technique allows to perform DPI with
a completely independent Probe and does not require to modify the endpoints and require
them to work properly.• Cipher suite completeness: this criterion will be Yes if no limitation on cipher suite
selection is introduced. Otherwise if only some cipher suites can be used, it will be No.
• Difficulty to inject packets: can be Same/Easier where Same means same difficulty of the
case when no DPI has to be performed (e.g. the TLS using ephemeral ciphersuites,periodic renewal of session keys, etc).
• Difficulty to steal data: scale as previous point.
Performance impact
• Real time or delayed: this criterion will say if DPI is performed in real time traffic or on
historical/delayed data.• Adds constant delays to each frame: is a Yes/No criterion specifying if this technique
requires some computation on the endpoints for each application frame to be sent or
received.• Requires more bandwidth: if Yes, it means that some additional packets have to be
transmitted from/to the endpoints, and thus additional bandwidth will be required.
• Requires more CPU power: if Yes, it means that the endpoints will need additional CPU
power to accomplish DPI-re...
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