Conference article

We present a unique item in the history of cryptography: a woollen carpet woven in a Uruguayan penitentiary in 1980 during the dictatorship in that country. The colors of a pair of horizontally adjacent knots encrypt a single letter. The carpet is in moderately good shape, with loss of colors and some damage by moths. We had obtained the original code and here report on the deciphering. The plaintext is a political message destined to comrades outside, with a description of the political situation and directives for actions. The cryptosystem is a simple substitution. Breaking such codes is trivial. The real task here is to translate the knots into a machine-readable representation of their colors, in the presence of unclear colors and damage to parts of the carpet. The encrypted carpet is an important document from the dark times of the Uruguayan dictatorship, manufactured by prisoners from the guerrilla movement Tupamaros. Two of the present authors (JJC and JT) were active members of this group. Their personal memories were essential for our successful reconstruction of the plaintext.

No keywords available

José Pedro Charlo. 2014. El almanaque. Documentary movie. Argentina, Spain, Uruguay.

Charles Dickens. 1859. A Tale of Two Cities. Chapman & Hall, London.

Steven K. Feiner James D. Foley, Andries van Dam and John F. Hughes. 1990. Computer Graphics Principles and Practice. Adisson Wesley.

William M. Newman and Robert F. Sprouil. 1983. Principles of Interactive Computer Graphics. Mc Graw Hill.

Jorge Tiscornia. 2012. El almanaque. Yaugurú, Montevideo, Uruguay.

Jorge Tiscornia. 2014. Nunca en domingo. Relatos. Penal de Libertad 1972-1985. Ediciones de la Banda Oriental, Montevideo, Uruguay.

Jacqueline Tobin. 1999. Hidden in Plain View. A secret story of quilts and the underground railway. Anchor Books, New York.