  With the advancement of technology in the last few decades, leading to the
widespread availability of miniaturized sensors and internet-connected things
(IoT), security of electronic devices has become a top priority. Side-channel
attack (SCA) is one of the prominent methods to break the security of an
encryption system by exploiting the information leaked from the physical
devices. Correlational power attack (CPA) is an efficient power side-channel
attack technique, which analyses the correlation between the estimated and
measured supply current traces to extract the secret key. The existing
countermeasures to the power attacks are mainly based on reducing the SNR of
the leaked data, or introducing large overhead using techniques like power
balancing. This paper presents an attenuated signature AES (AS-AES), which
resists SCA with minimal noise current overhead. AS-AES uses a shunt
low-drop-out (LDO) regulator to suppress the AES current signature by 400x in
the supply current traces. The shunt LDO has been fabricated and validated in
130 nm CMOS technology. System-level implementation of the AS-AES along with
noise injection, shows that the system remains secure even after 50K
encryptions, with 10x reduction in power overhead compared to that of noise
addition alone.
