It has been known for over 30 years that the existence of a large-scale, general-purpose quantum computer would render existing public-key cryptography (both encryption and digital signatures) insecure. While this sounds quite bad, note that it is currently unclear when such quantum computers might become available. Part of the problem is that an attacker can record and store encrypted data now, and then use a quantum computer – when one becomes available – to break the encryption and recover the underlying data.