Session Authenticity is the last requirement in the System and Communications Protection (03.13) family, and it is the control that keeps a communications session trustworthy from end to end. It is what stops an attacker from stepping into the middle of a session or hijacking one already in progress. Session Authenticity (03.13.15) requires protecting the authenticity of communications sessions. Per the NIST discussion, protecting session authenticity addresses communications protection at the session level rather than at the packet level, and it establishes grounds for confidence at both ends of the session in the ongoing identities of the other parties and the validity of the transmitted information.
A common difficulty with this requirement is assuming that encrypting traffic covers it. Encryption protects confidentiality, but authenticity is about knowing the party on the other end is still who they claimed to be and that the session has not been tampered with. Per the NIST discussion, authenticity protection includes protecting against adversary-in-the-middle attacks, session hijacking, and the insertion of false information into sessions.
Where things stand for companies facing the transition from NIST 800-171 R2 to R3:
The following is reproduced verbatim from NIST 800-171 R3, requirement 03.13.15 Session Authenticity. Only the formatting has been adjusted for readability. This is a single statement with no lettered parts:
The source control is SC-23 from NIST 800-53. There are no Organization-Defined Parameters (ODPs). Per the NIST discussion, this protection operates at the session level, not the packet level, and covers adversary-in-the-middle attacks, session hijacking, and the insertion of false information into sessions. You can read the requirement directly at NIST 800-171 R3, 03.13.15 (p. 63).
None (0). Requirement 03.13.15 contains no bracketed assignment, so there is no organization-defined value to select and nothing for the DoD to specify. The requirement applies as written.
Your System Security Plan (SSP) narrative for 03.13.15 therefore records how the requirement is implemented rather than a parameter you chose.
NIST 800-171A R3 breaks 03.13.15 into one (1) determination statement, and it has no Organization-Defined Parameters (ODPs). This AO is:
This is one of the simplest objectives in the entire publication, but the simplicity is deceptive: an assessor still expects to see the mechanisms that provide session authenticity. The full guidance on assessment methods and objects, is in NIST 800-171A R3, 03.13.15 (p. 83).
Examine: system and communications protection policy and procedures; procedures for session authenticity; system design documentation; system configuration settings; system audit records; system security plan.
Interview: personnel with information security responsibilities; system administrators.
Test: mechanisms for supporting or implementing session authenticity.
03.13.15 maps from NIST 800-171 R2 requirement 3.13.15 (protect the authenticity of communications sessions):
Mapped against the one (1) AO, it is direct (minimal effort), with no net-new AOs and none with no mapping. This is a clean carry-forward with identical wording. If you satisfied R2 3.13.15, confirm the same session authenticity mechanisms still apply to current systems and any services added since your last assessment.
Source Control in NIST 800-53 R5:
Secure Controls Framework (SCF) Crosswalk
Organizations running a single control set across multiple frameworks can satisfy 03.13.15 through the following SCF controls:
The crosswalks from NIST 800-171 R3 and NIST 800-171A R3 to the SCF are available at no cost through the SCF Set Theory Relationship Mapping (STRM): https://securecontrolsframework.com/start-here/set-theory-relationship-mapping-strm. The STRM also carries the relationship type for each mapping (Equal, Subset Of, Intersects With), which tells you whether an SCF control fully satisfies the requirement or only part of it. Mapping above taken from SCF 2026.3.
The following are issues teams may encounter rather than certainties. They are about distinguishing authenticity from confidentiality, each of which needs documented evidence of due diligence and due care such as policies, standards, procedures, and configuration screenshots:
Reasonable objective evidence for an assessment is often subjective. The following examples of evidence to address NIST 800-171 R3 03.13.15 are sourced from the SCF Evidence Request List (ERL), available at https://securecontrolsframework.com/free-content/scf-download. These ERL artifacts are mapped to NIST 800-171 R3 03.13.15 through SCF controls. They establish a starting point for discussions on what an organization needs to have for evidence of due diligence and due care to withstand external scrutiny by an assessor or regulator.
The SCF controls that carry this requirement have no dedicated ERL artifact, so evidence rests on the configuration and records that demonstrate the objectives directly.
Alongside these, keep the System Security Plan (SSP) narrative for 03.13.15.
With the single AO mapping directly, 03.13.15 is a light lift focused on confirming and documenting existing mechanisms. A realistic sequence:
How many assessment objectives does NIST 800-171 R3 03.13.15 have? NIST 800-171A R3 breaks 03.13.15 into one (1) assessment objectives. An assessor works through each one separately, so each needs its own evidence.
Which NIST 800-53 R5 control does NIST 800-171 R3 03.13.15 come from? SC-23.
How many Organization-Defined Parameters (ODPs) does NIST 800-171 R3 03.13.15 have? None (0). The requirement contains no bracketed assignment, so there is no organization-defined value and nothing for the DoD to specify.
Where does NIST 800-171 R3 03.13.15 sit in the NIST 800-171 R3 Kill Chain? Phase 19, Cryptographic Key Management. The Kill Chain is a phased model for sequencing R3 implementation, and it assigns this requirement to that phase.
03.13.15 Session Authenticity protects the authenticity of communications sessions at the session level, guarding against adversary-in-the-middle attacks, session hijacking, and false information inserted into a session. It maps directly from R2 3.13.15 with identical wording, so there is no net-new work. The recurring problem is treating encryption as the answer. Identify your sessions, confirm the mechanisms that establish confidence in both ends of the conversation, and document them.
Authoritative sources:
Authoritative sources:
This guide reproduces U.S. Government text from NIST 800-171 R3 and NIST 800-171A R3. It is educational, not legal or assessment advice. Last reviewed: 2026-09-22.
