falsifiable

The sentence "It will rain tomorrow" is falsifiable, while the sentence "It is what it is" is not.

A digital signature algorithm must be not falsifiable.

The statement It rains every day, everywhere is falsifiable, because it is contradicted by the basic statement On the third of August, in New York city it was not raining and it is not contradicted by the basic statement On the second of August, in New York city it was raining, while the statement It will rain someday is not falsifiable.