It should be noted that quantum computers are a threat mainly for interactions between unrelated parties which perform legal activities, e.g. online shopping, online banking, notarized legal documents that use long-term digital signatures.

Quantum computers are not a threat for spies or for communications within private organizations where security is considered very important, where the use of public-key cryptography can easily be completely avoided and authentication and session key exchanges can be handled with pre-shared secret keys used only for that purpose.