What are the underlying assumptions, especially with regards to the cost to potential attackers, (threat model) of the NIST minimum 112 bits recommendation for US government in 800-63B?

Question

What are the underlying assumptions, especially with regards to the cost to potential attackers, (threat model) of the NIST minimum 112 bits recommendation for US government in 800-63B?

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Answer 1

The definitions in that document ultimately trace back to https://nvlpubs.nist.gov/nistpubs/Legacy/SP/nistspecialpublication800-57p1r3.pdf, which indicates that 80 bit keys are already to be considered compromiseable, and that 112 bit keys can only be trusted until 2030.

The assumptions don’t appear to be explicitly stated, but are likely based in Moore’s law, assuming that computers will continue to improve exponentially, and extrapolating to the future point where an acceptable average time to compromise has decreased to an unacceptable value.