In cryptography world I usually encounter the word "infeasible", like:

"It is computationally infeasible to solve elliptic curve discrete logarithm."

But I rarely see the word "impossible" being used in cryptography. Is there some actual difference between these two words? I'm not native speaker so forgive me if it is too obvious question.

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  • 5
    Lexico gives the meaning of infeasible as: Not possible to do easily or conveniently; impracticable. So it does not mean 'impossible' but 'difficult' or 'unrealistic'. Jun 22 at 22:07
  • 1
    The infeasible we do immediately; the impossible takes longer. Jun 22 at 22:41
  • "Feasible" is part of the folklore of engineering and optimization. I think that's why. Jun 22 at 23:42
  • The word impossible in math has a much stronger meaning than difficult. The word infeasible might refer to something that could be feasible with more computing power, or quantum computers. Jun 23 at 1:02

1 Answer 1


Cambridge Dictionary - "impossible":

An impossible situation is extremely difficult to deal with or solve

This suggests something is extremely difficult and will take a long time to solve. You could also say it is literally impossible to solve and cannot be solved.

Lexico Dictionary - "infeasible":

Not possible to do easily or conveniently; impracticable

This also means difficult/unrealistic/impracticable

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