Cryptography Reference
In-Depth Information
The Western Schism
When Pope Urban VI (1378-1389) was elected pope in 1378, it began the
great
Western Schism
in the Roman Catholic Church, plaguing it for four
decades. Although competent, Urban became a tyrannical reformer, which led
to the revolt by the thirteen French cardinals led by
Robert de Geneve
. They
left Rome and four months later declared Urban's election “null”, because they
felt that it had been made under a cloud of fear. On September 20, 1378, they
elected Robert de Geneve as
Clement VII
(1342-1394), the first
antipope
(one
elected to be pope in opposition to one canonically chosen, in this case, Urban).
The new antipope now saw a clear need for a cryptosystem for his new enter-
prise at his new home in Avignon, France. One of his secretaries was Gabrieli
di Lavinde, from Parma, who took up the task. In 1379, he devised a combi-
nation of code (book) and cipher. (Recall the definitions of
cipher
[page 4] and
code book
[page 6].) He established not only a simple substitution cipher, but
also a list (code book) of plaintext words together with two-letter ciphertext
equivalents, which came to be known as a
nomenclator
, a cross-breeding of the
code (book) and the cipher. To envision this, think of a telephone book as half
of a nomenclator, with the telephone number as the code. The other half is
a means to turn a telephone number into the name without having to search
the entire book knowing only the phone number. Such mechanisms for
reverse
directories
would be the other half, or cipher half of the nomenclator, as a sim-
ple illustration. For more than four and a half centuries nomenclators would
be used throughout Europe. Although Lavinde's code book consisted of only a
few plaintext/ciphertext pairs, it grew to more than several thousand over the
centuries.
It is worth mentioning the outcome of the schism. European countries were
divided over the pope/antipope dispute; the Aragon, Castile, France, Navarre,
Portugal, Savoy, and Scotland sided with Clement, while Bohemia, Flanders, the
Holy Roman Empire, Hungary, north/central Italy, and Poland backed Urban.
The Papal States fell into anarchy. When Urban died in Rome on October 15,
1389, it was suspected that he was poisoned. When Clement went to his grave
on September 16, 1394, in Avignon, he still believed in his legitimacy, and this
was echoed by King Charles V, who on that day, proclaimed him “the true
Shepherd of the Church.” In 1409, with the Roman pope, Gregory XII, and the
Avignon antipope, Benedict XIII, both in power, the cardinals met at a council
in Pisa, and elected a
third
pope Alexander V, succeeded shortly thereafter by
John XXIII. The German King Sigismund wanted an end to the schism, so he
convinced John XXIII, in 1414, to hold the Council of Constance. The council
deposed him, received the resignation of Gregory XII, and dismissed the claims
of Benedict XIII. In November of 1417, pope Martin V was elected, and the
schism ended.
Geoffrey Chaucer
Another of the few cryptographic authors of the Middle Ages, but perhaps
the most famous, was Geoffrey Chaucer (1342-1400), who was easily the most
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