Exploitation of OTFTs variability for PUFs implementation and impact of aging

On the Aging of OTFTs and Its Impact on PUFs Reliability

“…In this regard, the usual operating conditions of this kind of device can be a serious drawback because the required biasing could trigger aging mechanisms that progressively degrade the organic materials' properties and the device performance, leading to a time-dependent variability (TDV). Actually, in our previous work [11], we observed that the drift of the drain current in the OTFTs during operation could end in a change in the PUF output, with a consequent reduction in the PUF reliability. Therefore, a complete evaluation of the performance/reliability of PUFs requires a detailed study of the aging mechanisms that are involved in the materials used for the fabrication of OTFTs and their impact on the electrical characteristics of these devices [10].…”

“…In this work, we have considered a PUF that uses the current through the channel (I D ) of the device as the source of entropy, i.e., the drain current is the challenge from which the PUF provides a key as response. As a mapping function for key generation, the digitalization of the I D current into a given number of bits is considered [11]. Keys are generated by concatenating the words provided by several OTFTs.…”

“…As for the reliability of the PUFs, i.e., the reproducibility of the generated fingerprints, our previous work [11] showed that, considering device aging during an HCI-like stress, the associated shift of the device current could be a drawback for this kind of application. However, those preliminary results also showed that the current shift saturates with the stress time, suggesting that the application of a carefully chosen stress previously to the PUF operation may be beneficial for its reliability.…”

“…Since the fabrication of organic materials is not a mature enough process yet, the devices show high initial variability (i.e., Time-Zero Variability, TZV). On the positive side, TZV of Organic TFTs (OTFTs) is continuously improving as the technology matures (and, consequently, their performance as well) but, also, the large performance variability of the OTFTs can be exploited for some security and cryptography applications [11]. The randomness associated to the heterogeneous nature of organic materials and the fabrication processes can be used as a source of entropy for the implementation of Physical Unclonable Functions (PUFs) [11][12][13].…”

“…On the positive side, TZV of Organic TFTs (OTFTs) is continuously improving as the technology matures (and, consequently, their performance as well) but, also, the large performance variability of the OTFTs can be exploited for some security and cryptography applications [11]. The randomness associated to the heterogeneous nature of organic materials and the fabrication processes can be used as a source of entropy for the implementation of Physical Unclonable Functions (PUFs) [11][12][13]. However, the reliability of OTFT devices is another issue of concern due to its direct impact on the PUFs' reliability, i.e., for the reproducibility of the cryptographic key.…”