  Cloud computing for storing data and running complex algorithms have been
steadily increasing. As connected IoT devices such as wearable ECG recorders
generally have less storage and computational capacity, acquired signals get
sent to a remote center for storage and possible analysis on demand. Recently,
compressive sensing (CS) has been used as secure, energy-efficient method of
signal sampling in such recorders. In this paper, we propose a secure procedure
to outsource the total recovery of CS measurement to the cloud and introduce a
privacy-assured signal recovery technique in the cloud. We present a fast, and
lightweight encryption for secure CS recovery outsourcing that can be used in
wearable devices, such as ECG Holter monitors. In the proposed technique,
instead of full recovery of CS-compressed ECG signal in the cloud, to preserve
privacy, an encrypted version of ECG signal is recovered by using a randomly
bipolar permuted measurement matrix. The user with a key, decrypts the
encrypted ECG from the cloud to obtain the original ECG signal. We demonstrate
our proposed method using the ECG signals available in the MITBIH Arrhythmia
Database. We also demonstrate the strength of the proposed method against
partial exposure of the key.
