During the recent development of information technology and the prevalent breakthroughs of its services, more digital data tend to be readily stored online. Although the massive advantages, there is a pivotal necessity for curating digital data forgetting. Online content can pose perilous threats in terms of privacy and security that may hinder the right to be forgotten, encompassed by the GDPR act, since the released data can be archived and accessed retrospectively. Prior approaches focused on various access heuristics and elastic expiration times to make the data unreachable to some extent. However, there are still many pending issues related to the proposed studies, such as securing ephemeral key storage and co-ownership data deletion. In this paper, we attempt to tackle the problem of storing ephemeral keys during the estimated validity period. Hence, we devise a novel concept called key decay over time, which can achieve the ephemeral existence of the key. The decay idea entails the gradual, irreversible corruption of the key with time passing. In the current work, we combine the concept of gradual time elapsing and corruption into a single notion of the decay rate. Meanwhile, the irreversibility merit formed by randomness and various obfuscation strategies impedes retrospective attacks. Over time, the decay rate will give an estimated range for the key to be destroyed entirely. Finally, we implement and thoroughly assess a proof-of-concept regarding the key decay, including computational complexity and security analysis.