Encryption by Heart (EbH)-Using ECG for time-invariant symmetric key generation

Wearable devices are a part of Internet-of-Things (IoT) that may offer valuable data of their porting user. This paper explores the use of ElectroCardioGram (ECG) records to encrypt user data. Previous attempts have shown that ECG can be taken as a basis for key generation. However, these approaches do not consider time-invariant keys. This feature enables using these so-created keys for symmetrically encrypting data (e.g. smartphone pictures), enabling their decryption using the key derived from the current ECG readings. This paper addresses this challenge by proposing EbH, a mechanism for persistent key generation based on ECG. EbH produces seeds from which encryption keys are generated. Experimental results over 24 h for 199 users show that EbH, under certain settings, can produce permanent seeds (thus time-invariant keys) computed on-the-fly and different for each user-up to 95.97% of users produce unique keys. In addition, EbH can be tuned to produce seeds of different length (up to 300 bits) and with variable min-entropy (up to 93.51). All this supports the workability of EbH in a real setting.