Poul-Henning Kamp is the lead architect and developer for the open source Varnish cache project, an HTTP accelerator. He is responsible for the widely used MD5 password hash algorithm, a vast quantity of systems code, including the FreeBSD GEOM storage layer, GBDE cryptographic storage transform, part of the UFS2 file system implementation, FreeBSD Jails, malloc library and the NTP timecounters code.