A Homophonic Substitution in the Archives of the Last Great Pensionary of Holland. - Karl de Leeuw; Hans van der Meer (Cryptologia, 1993)

A Turning grille from the Ancestral Castle of the Dutch Stadtholders. - Karl de Leeuw; Hans van der Meer (Cryptologia, 1995)

Johann Friedrich Euler (1741-1800): Mathematician and Cryptologist at the Court of the Dutch Stadholder William V. - Karl de Leeuw (Cryptologia, 2001)

The Dutch Invention of the Rotor Machine, 1915-1923. - Karl de Leeuw (Cryptologia, 2003)

Preface. - Karl de Leeuw (Sci. Comput. Program., 2007)

Bitcoin and Beyond: Exclusively Informational Monies - Jan A. Bergstra; Karl de Leeuw (CoRR, 2013)

Questions related to Bitcoin and other Informational Money - Jan A. Bergstra; Karl de Leeuw (CoRR, 2013)

Review of Forschungsstelle Langeveld: Duits Afluisterstation in bezet Nederland by Hans Knap. - Karl de Leeuw (Cryptologia, 2013)

J. F. W. Nuboer and the Reintroduction of Machine Cryptography by the Royal Netherlands Navy, 1915-1940. - Karl de Leeuw (Cryptologia, 2015)

The Solving of a Fleissner Grille during an Exercise by the Royal Netherlands Army in 1913. - Karl de Leeuw (HistoCrypt, 2018)

Decryption of historical manuscripts: the DECRYPT project. - Beáta Megyesi; Bernhard Esslinger; Alicia Fornés; Nils Kopal; Benedek Láng; George Lasry; Karl de Leeuw; Eva Pettersson; Arno Wacker; Michelle Waldispühl (Cryptologia, 2020)

Keys with nomenclatures in the early modern Europe. - Beáta Megyesi; Crina Tudor; Benedek Láng; Anna Lehofer; Nils Kopal; Karl de Leeuw; Michelle Waldispühl (Cryptologia, 2024)