  Digital Twins (DT) virtually model cyber-physical objects using Internet of
Things (IoT) components (e.g., sensors) to gather and process senstive
information stored in the cloud. Trustworthiness of the streamed data is
crucial which requires quantum safety and breach resiliency. Digital signatures
are essential for scalable authentication and non-repudiation. Yet, NIST PQC
signature standards are exorbitantly costly for low-end IoT without considering
forward security. Moreover, Post-Quantum (PQ) signatures lack aggregation,
which is highly desirable to reduce the transmission and storage burdens in
DTs. Hence, there is an urgent need for lightweight digital signatures that
offer compromise resiliency and compactness while permitting an effective
transition into the PQ era for DTs.
  We create a series of highly lightweight digital signatures called
Hardware-ASsisted Efficient Signature (HASES) that meets the above
requirements. The core of HASES is a hardware-assisted cryptographic commitment
construct oracle (CCO) that permits verifiers to obtain expensive commitments
without signer interaction. We created three HASES schemes: PQ-HASES is a
forward-secure PQ signature, LA-HASES is an efficient aggregate Elliptic-Curve
signature, and HY-HASES is a novel hybrid scheme that combines PQ-HASES and
LA-HASES with novel strong nesting and sequential aggregation. HASES does not
require a secure-hardware on the signer. We proved that HASES schemes are
secure and implemented them on commodity hardware and an 8-bit AVR ATmega2560.
Our experiments confirm that PQ-HASES and LA-HASES are two magnitudes of times
more signer efficient than their PQ and conventional-secure counterparts,
respectively. HY-HASES outperforms NIST PQC and conventional signature
combinations, offering a standardcompliant transitional solution for emerging
DTs. We open-source HASES schemes for public testing and adaptation.
