Project
| # | Title | Team Members | TA | Documents | Sponsor |
|---|---|---|---|---|---|
| 4 | Secure Chain-of-Custody Container |
Alp Oguz Selim Mamak Sena Tiryaki |
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| **Team Members:** - Selim Mamak (smamak2) - Serdar Alp Oguz (soguz2) - Sena Bahar Tiryaki (stiry2) ## Problem Confidential engineering prototypes may need to be transported between labs, offices, and authorized employees before they are publicly released. A standard locked case can restrict access, but it provides little information about who opened it, when it was opened, or whether someone attempted to bypass the lock or tamper with the enclosure. Paper custody logs depend on users recording every interaction and can be modified after the fact. Shipping data loggers may record events such as impact or temperature but generally do not control access, while electronic lockboxes primarily focus on restricting entry rather than maintaining a detailed physical tamper and custody history. A reusable system that combines controlled access, tamper detection, and persistent event logging could provide a more complete electronic chain-of-custody record. ## Solution Overview We will build a battery-powered secure container that opens only for authorized NFC credentials and records access and physical tamper events. An electronic latch will control access, while a lid sensor, conductive tamper loop, and accelerometer will monitor the enclosure for unauthorized opening, physical damage, and significant impact events. Each event will be time stamped and stored in nonvolatile memory. Event records will be hash-linked so that modification of previously stored records can be detected when the log is exported and verified. Low-power operation will be a major engineering focus of the project. Because the container may remain unused for long periods, the design will minimize standby consumption using low-power sensing components and power gating. Higher-power components such as the NFC reader and electronic latch circuit will normally remain disabled and will only be powered when needed. The complete system will be implemented using a custom PCB containing the microcontroller, power-management circuitry, sensor interfaces, storage, NFC interface, and latch-control circuitry. ## Solution Components ### 1. Power Subsystem The container will use a protected rechargeable Li-Po battery with USB-C charging. Low-quiescent-current regulation and power gating will be used to reduce standby power consumption. The NFC reader and electronic latch circuit will normally remain powered off. A low-power wake mechanism, such as a Hall-effect sensor or pushbutton, will activate the main system when a user wants to authenticate without requiring the NFC reader to continuously scan. Low-power sensors used for enclosure monitoring will remain active while the rest of the system is in standby. The firmware will control transitions between standby, wake, authentication, latch actuation, event logging, and return to standby. Battery voltage and current consumption will be measured so that standby and active-state power consumption can be experimentally characterized. ### 2. Access Control and Tamper Sensing Subsystem An NFC reader and enrolled credentials will identify authorized users. The exact NFC reader and credential pair will be selected through early compatibility testing. The design will use authenticated credentials rather than relying only on a card UID, which would provide weaker access control. An electronically controlled latch will remain mechanically locked when unpowered and will only consume significant power during lock or unlock actuation. A Hall-effect sensor will determine whether the container lid is open or closed. A conductive tamper loop routed through protected portions of the enclosure will detect interruption caused by cutting, drilling, or other physical penetration. A low-power accelerometer will detect significant impacts above a defined threshold. Tamper and lid events will wake the control system so that suspicious activity can be time stamped and recorded even while the system is normally operating in its low-power state. ### 3. Control, Logging, and Readout Subsystem A low-power microcontroller will coordinate access control, sensing, power management, latch control, and event logging. A real-time clock with backup power will maintain accurate timestamps if the main battery is disconnected or replaced. Nonvolatile FRAM will store event records containing the event type, timestamp, and user identity when applicable. The event records will be hash-linked so that altering a previously stored record can be detected when the history is verified. A USB-C connection will allow the event history to be transferred to a computer. A simple desktop program will display the stored chain-of-custody record and indicate whether the log passes its integrity check. ## Criterion for Success 1. **Authorized Access:** The container remains locked until an enrolled NFC credential is successfully authenticated. An authorized access is recorded with the user identity and timestamp, while an unenrolled credential is denied access. 2. **Tamper Detection:** Opening the lid without authorization, breaking the conductive tamper loop, and producing a predefined significant-impact event are individually detected and recorded with timestamps. 3. **Low-Power Operation:** The completed system achieves a measured standby current below **100 µA** while the NFC reader and latch circuitry are inactive. Standby, authentication, and latch-actuation current will be measured and documented. 4. **Reliable Locking:** The electronic latch performs at least **20 consecutive authorized lock/unlock cycles** without resetting or disrupting the control electronics. 5. **Persistent Event Logging:** Stored event records remain available after complete loss of the main battery, and modifying an existing stored record causes the log-integrity verification software to report an error. 6. **Timestamp Preservation:** The real-time clock continues to maintain time during a main-battery removal and provides correct timestamps after the main system is powered again. ## Alternatives A standard mechanical lockbox provides physical access restriction but does not automatically identify users or maintain an electronic record of access and tamper events. Electronic lockboxes can provide credential-based access control, but their primary purpose is generally controlling entry rather than monitoring multiple forms of physical tampering and maintaining a persistent chain-of-custody history. Shipping data loggers provide another alternative and can measure events such as shock or environmental conditions during transportation, but they generally do not physically control access to the protected contents. Our project combines **identity-linked access control, physical tamper detection, persistent timestamped logging, and low-power battery operation** in a single reusable container intended for maintaining the custody history of confidential engineering prototypes. |
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