IEC 62351-5:2023 defines the application profile (A-profile) secure communication mechanism specifying messages, procedures and algorithms for securing the operation of all protocols based on or derived from IEC 60870-5, Telecontrol Equipment and Systems – Transmission Protocols.
For the measures described in this document to take effect, they must be accepted and referenced by the specifications for the protocols themselves. This document is written to enable that process.
The subsequent audience for this document is intended to be the developers of products that implement these protocols.
Portions of this document may also be of use to managers and executives in order to understand the purpose and requirements of the work.
This document is organized working from the general to the specific, as follows:
• Clauses 2 through 4 provide background terms, definitions, and references.
• Clause 5 describes the problems this specification is intended to address.
• Clause 6 describes the mechanism generically without reference to a specific protocol.
• Clauses 7 and 8 describe the mechanism more precisely and are the primary normative part of this specification.
• Clause 9 define the interoperability requirements for this secure communication mechanism.
• Clause 10 describes the requirements for other standards referencing this document.
The actions of an organization in response to events and error conditions described in this document are expected to be defined by the organization’s security policy and they are beyond the scope of this document.

This International Standard cancels and replaces IEC TS 62351-5 published in 2013. It constitutes a technical revision. The primary changes in this International Standard are:
a) The secure communication mechanism is performed on per controlling station/controlled station association.
b) User management to add, change or delete a User, was removed.
c) Symmetric method to change the Update Key was removed.
d) Asymmetric method to the change Update Key was reviewed.
e) Challenge/Reply procedure and concepts were removed.
f) Aggressive Mode concept was replaced with the Secure Data message exchange mechanism.
g) Authenticated encryption of application data was added.
h) The list of permitted security algorithms has been updated.
i) The rules for calculating messages sequence numbers have been updated
j) Events monitoring and logging was added