Volume 8 (2012) Article 8 pp. 197-208
The Communication Complexity of Gap Hamming Distance
In the gap Hamming distance problem, two parties must determine whether their respective strings $x,y\in\{0,1\}^n$ are at Hamming distance less than $n/2-\sqrt n$ or greater than $n/2+\sqrt n.$ In a recent tour de force, Chakrabarti and Regev (2010) proved the long-conjectured $\Omega(n)$ bound on the randomized communication complexity of this problem. In follow-up work, Vidick (2010) discovered a simpler proof. We contribute a new proof, which is simpler yet and a page-and-a-half long.