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CIoTSP: IoT Architecture and Security Fundamentals

CIoTSP · Work through your exam, one topic at a time.

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IoT Architecture and Security Fundamentals

Domain 1 asks you to read an IoT deployment as a layered system and to justify where each control sits. Items typically present a topology - sensors, gateways, edge nodes, cloud services, operator apps - and ask which boundary is weakest or which control belongs at which tier.

Reference architectures you must be able to label

  • Four-tier IoT model: perception/things (sensors, actuators, RTUs), network/transport (gateways, LPWAN, 5G), processing (edge/fog nodes, brokers, stream analytics), application (dashboards, APIs, business systems).
  • Edge vs fog: edge sits on or beside the device (a gateway on the plant floor); fog is intermediate compute between edge and cloud. Marks are lost by treating the two as synonyms.
  • Purdue / ISA-95 for OT: Level 0 process, 1 basic control (PLC), 2 supervisory (HMI/SCADA), 3 site operations, 3.5 DMZ, 4 enterprise IT, 5 external. Traffic crosses levels only through defined conduits; nothing skips the 3.5 DMZ.
  • ISA/IEC 62443 zones and conduits: group assets by shared risk and required security level, then permit traffic only through explicit conduits.

Constrained-device realities

RFC 7228 classes 0–2 define capability tiers. Class 0 devices cannot run standard TLS/HTTP stacks and need gateway-assisted security (DTLS with raw public keys, OSCORE, or a terminating gateway). Assume nothing about on-device cryptography until you have identified the class.

Fundamentals mapped to IoT

Confidentiality, integrity and availability shift emphasis: OT weights availability and integrity above confidentiality. Device identity, supply-chain integrity and physical accessibility become first-class concerns. A root of trust is architectural - if there is no immutable boot ROM and signer key, no downstream control can be trusted.

Worked example

A water utility wants cloud analytics on PLC tank levels. Direct internet egress from the SCADA server fails review because a Level 2 asset must not hold a bidirectional path to Level 4/5. Correct design: a historian or OPC UA gateway in the Level 3.5 DMZ performs store-and-forward and protocol break (OPC UA to MQTT), with an allow-listed destination and no inbound session into Level 2.

Traps that cost marks

  • Putting a cloud broker directly inside a control zone because the traffic is encrypted.
  • Forgetting actuators: a compromised sensor lies, a compromised actuator causes damage.
  • Claiming TLS 1.3 on an 8-bit class 0 node.
  • Skipping asset enumeration - you cannot zone what you have not inventoried.