Books are traditionally printed on large sheets containing multiple pages which are then folded repeatedly until each page is in place. Technically, a ‘signature’ is a letter of the alphabet placed at the bottom of the first page of each sheet, denoting the order in which the sheets occur within the book. Today the sheets themselves are commonly referred to as signatures.
Part of the disappearing legacy of print technology, printers’ signatures also constitute an accidental form of encryption.
Just as, faced with a signature sheet containing 8, 16, or 32 pages, it is difficult to work out which page will end up where (the ‘Printer’s Transformation’ as a primitive version of the Baker’s Transformation), once a number of signatures is gathered, the folded edges are trimmed off and the book takes on its final form as a linear series of single pages, information about the relation of pages to signatures and the original structure of the book is effectively lost—a paper trapdoor.
More recent print-on-demand technology dispenses with the use of signatures entirely, and of course in relation to ebooks they are an irrelevant archaism. And yet not only do signature foldings (8, 16, 32) have a certain relation to binary arithmetic, signatures can be used as a form of book cipher (or rather a pre-book cipher, since the information necessary for decoding is destroyed once the book is bound)
Extending the paradox of using the traditional litho print method to publish a book on digital art, the Artist’s Signature Edition of Proof of Work includes a hard copy of the book along with one of the 16-page print signatures (900 x 640mm) that make it up. Each signature is signed and annotated by the artist with the key to a crypto puzzle trail that leads to a numbered electronic edition of Proof of Work. Signatures can be unfolded and displayed as a double-sided poster.
16 signature editions were produced, each featuring a different signature from the book.