In the everything-old-is-new-again department, this article describes the authentication system used by the artist Banksy. It has two numismatic
connections. First, it involves examples of the artist's own genuine/fake "Di-faced tenner" notes, and a random tear in the note just like the
system used for indentured notes in the U.S. colonial era (and long before that into medieval times). -Editor
Banksy's Di-faced Tenner
Part of the appeal of the artist Banksy is his/her/their anonymity. Despite continuing announcements of Banksy's identity being revealed, no one is really
sure who Banksy is (and to further add to the confusion, a well-known time traveler recently hinted that she was - or maybe wasn't - Banksy). Regardless,
collectors of art by an anonymous creator face a difficult problem of authenticating any individual artwork. For a public piece of graffiti, Banksy's official
website will confirm or deny whether it was painted by the artist.
But how do you know that the print or painting you're buying is the real deal? Gallery authenticity certificates can be as readily forged as paintings. So
in 2009, Banksy launched Pest Control, a not-for-profit company to sell and authenticate artworks. Basically, you submit images of the print or artwork, and if
it is deemed authentic, for £65, you receive a certificate of authenticity, which includes half of a "Di faced tenner", a torn in half fake £10 note
created by Banksy with Lady Diana's face on it (an example can be seen here). The half-note has a handwritten ID number on it which can be matched to the other
half of the note held by Pest Control.
This offers a fairly clever authentication system:
The tear is what uniquely separates the private key, the half of the note kept secret under lock and key at Pest Control, with the public key. The public
key is the half of the note attached to the authentication certificate which gets passed on with the print, and allows its authenticity to be easily
We have no idea what has been written on Pest Control's private half of the note. Which means it can't be easily recreated, and that empowers Pest Control
to keep the authoritative list of who currently owns each authenticated Banksy work.
Even if you could somehow duplicate the exact tear in the middle of the note, you still don't have the private key held by Pest Control. When a work is
sold, one submits a change of ownership request which requires an image of the authentication certificate. Further, Pest Control then contacts the person they
have listed as the current owner of the work for confirmation.
It's a smart piece of cryptographic engineering, although as one commenter points out, not all that original. Chirographs have been used to determine
authenticity dating back to Medieval times. Sometimes, old ideas (even really old ideas) still have value.
To read the complete article, see:
Art Authentication: Banksy's Chirograph System
Here are examples of indented notes from earlier E-Sylum articles. -Editor
New-York 6% Six Month Loan Certificate
And here are links to definitions of the related terms "Chirograph" and "Indenture". -Editor
To read the earlier E-Sylum articles, see:
BRITISH MUSEUM ACQUIRES BANKSY £10 NOTE (https://www.coinbooks.org/v22/esylum_v22n05a33.html)
IN LETTERS WE TRUST: BANKNOTE TYPOGRAPHY
NEWMAN HISTORIC AMERICAN FISCAL PAPER : Lot 89390: New-York 6% Six Month Loan Certificate
Wayne Homren, Editor
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