ZLIB_POLY or PNG_POLY? I am not 100% sure which name is better. Historically, png and zlib were introduced at the same time as parts of one project. When searching through these documents: http://tools.ietf.org/html/rfc1950 http://tools.ietf.org/html/rfc1952 http://tools.ietf.org/html/rfc2083 this polynomial is defined in the one describing png format. The zlib/gzip documents reference it only in "Appendix: Sample CRC Code". We use the crc to calculate checksums of chunk files stored on chunkservers, data sent through the network and to create png files. Since we do not try to create gzip files maybe the PNG_POLY is a better choice. But it is still strange to use the name "PNG_POLY" when saving a chunk file :).