Janka hardness test understand which woods are harder than others. Janka hardness test The Janka hardness test (from the Austrian-born emigrant Gabriel Janka, 1864-1932) measures the resistance of a sample of wood to denting and wear. It measures the force required to embed an diameter steel ball halfway into a sample of wood. A common use of Janka hardness ratings is to determine whether a species is suitable for use as flooring. The hardness of wood varies with the direction of the wood grain. Testing on the surface of a plank, perpendicular to the grain, is said to be of "side hardness". Testing
Computational hardness assumption Computational hardness assumption In computational complexity theory, a computational hardness assumption is the hypothesis that a particular problem cannot be solved efficiently (where "efficiently" typically means "in polynomial time"). It is not known how to prove (unconditional) hardness for essentially any useful problem. Instead, computer scientists rely on reductions to formally relate the hardness of a new or complicated problem to a computational hardness assumption about a problem that is better-understood. Computational hardness assumptions are of particular importance in cryptography. A major goal in cryptography is to create cryptographic primitives with provable security. In some cases, cryptographic protocols are found