Poul-Henning Kamp

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Poul-Henning Kamp
Kamp in 2013
Other namesphk
Known forvarious contributions to FreeBSD and Varnish

Poul-Henning Kamp (Danish: [ˈpʰʌwl ˈhene̝ŋ ˈkʰɑmˀp]) is a Danish computer software developer known for work on various projects including FreeBSD and Varnish. He currently resides in Slagelse, Denmark.

Involvement in the FreeBSD project[edit]

Kamp with a plushie of Tux in 2000

Poul-Henning Kamp has been committing[1] to the FreeBSD project for most of its duration. He is responsible for the widely used MD5crypt implementation of the MD5 password hash algorithm,[2][3] 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, the phkmalloc implementation of the malloc library call, and the FreeBSD and NTP timecounters code,[4] and the nanokernel interface with David Mills.[5]

Varnish cache[edit]

He is the lead architect and developer for the open source Varnish cache project, an HTTP accelerator.

Dispute with D-Link[edit]

In 2006, Kamp had a dispute with electronics manufacturer D-Link in which he claimed they were committing NTP vandalism by embedding the IP address of his NTP servers in their routers.[6][7] The dispute was resolved in April 2006.[8]


FOSDEM 2014: "NSA operation ORCHESTRA Annual Status Report" by Kamp

A post by Kamp on the FreeBSD mailing lists[9][10] is responsible for the popularization of the term bike shed discussion, and the derived term bikeshedding, to describe Parkinson's law of triviality in open source projects - when the amount of discussion that a subject receives is inversely proportional to its importance. Poul-Henning Kamp is known for his preference of a Beerware license to the GNU General Public License (GPL).[11]


Poul-Henning Kamp has published a substantial number of articles over the years in publications like Communications of the ACM and ACM Queue mostly on the topics of computing and time keeping. A selection of publications:


  1. ^ "List of FreeBSD committers on FreeBSD.org".
  2. ^ "PHKs Bikeshed, MD5crypt Is No longer safe". Retrieved 13 March 2013.
  3. ^ Norris, Jeff (2004). "Mission-Critical Development with Open Source Software: Lessons Learned". IEEE Software. 21 (1). IEEE Computer Society: 42–49. doi:10.1109/MS.2004.1259211. S2CID 8324900.
  4. ^ Kamp, Poul-Henning (2002). "Timecounters: Efficient and precise timekeeping in SMP kernels" (PDF). Proceedings of the BSDCon Europe. EuroBSDcon. Netherlands. p. 10.
  5. ^ Mills, David; Kamp, Poul-Henning (2000). "The nanokernel". Proceedings of the 32th Annual Precise Time and Time Interval Systems and Applications Meeting. Precise Time and Time Interval Systems and Applications. Reston, Virginia, USA. pp. 423–430.
  6. ^ "D-Link Firmware Abuses Open NTP Servers".
  7. ^ Kamp, Poul-Henning. "Open Letter to D-Link about their NTP vandalism". Archived from the original on 2006-04-08.
  8. ^ Kamp, Poul-Henning (2006-04-27). "2006-04-27 Update – Open Letter to D-Link about their NTP vandalism". people.freebsd.org. Retrieved 2017-03-01.
  9. ^ "A bike shed (any colour will do) on greener grass...", freebsd-hackers mailing list, 1999
  10. ^ "Why Should I Care What Color the Bikeshed Is?". bikeshed.org. Retrieved 11 August 2020.
  11. ^ "Poul-Henning Kamp". Retrieved 10 January 2013.

External links[edit]

Media related to Poul-Henning Kamp at Wikimedia Commons