Re: VMs: Can one "prove" a hoax?

[Luis Vélez <legal1@xxxxxxxxxxxxx>]

Seeing we're discussing terms of proof or evidence, I thought appropriate to
paste here the Friedman (Elizabeth and William F.) rules by which to judge a
valid cipher (a negative of these could help prove a hoax?):

1) The first rule is that a cipher system must have rules; to use such
devices one must methodically follow the rules. A cipher unit (the
"cipher-text") is formed of one letter of the alphabet, and it must
correspond to another letter in the deciphered text (the "plaintext").

 2)There may be, and there often is, more than one rule; if there is a key
there may be more than one key. But the rules and the keys must be
unambiguous and they must be precisely applied.

3) Finding the right solution to a cryptogram is not a matter of opinion;
there must be scientific confirmation. Every decipherer must reach the same
conclusion. 

4) The plaintext solution must make sense; the message must say something.
However, a name alone may be sufficient to establish the authorship of the
work in which the cipher is found.

5) The cryptologist must become convinced that the solution could not have
happened by accident. If the odds against a chance occurrence of the
solution are one in a thousand million, his confidence in the decipherment
is justified. 

6) There must be a key to the cryptogram, such as a modification or
rearrangement of the alphabet which is used to reach the solution, and the
cryptogram must be of a reasonable length. For a mono-alphabetic
substitution cipher, about 25 letters are necessary before the cryptanalyst
can be sure that his is the only possible solution.

7) Whether or not the message may be considered to be long enough for
theoretical justification, corroboration of the cipher method, by the
analysis of other messages which yield to the same system, provides
conclusive proof. 

8) An allowance may be made for the mistakes of the encipherer. Every
solution must be considered on its own merits, but ordinarily not more than
about ten percent of such errors are tolerable.

9) To change the key, or alphabet, on a given signal is a common and
accepted practice in cryptography.

10) Acrostics, in which the first, last or other specific letters of
succeeding words constitute the cipher letters, have often been found in
literature and are an acceptable form of encipherment.

11) Discovery of an enciphered name (however spelled) leaves no doubt that
the author of the open text must also have been responsible for the message;
evidence of this kind must be taken as decisive.

12) The rules for selecting the letters of an acrostic must be invariable
and the letters must be chosen in a particular order. One cannot at random
select letters, whether in order or not; nor may one select letters in a
particular order and then rearrange them until an anagram is found that
represents a message or name.

13) Acrostics were popular in Elizabethan literature in which spelling was,
compared to modern orthography, very diverse. Even proper names were spelled
variably. The Friedmans go so far as to say this: "We should not be
surprised if it is claimed that acrostics appear in Shakespeare's works, for
they abounded in the literature of the time; nor should we be surprised if
these devices concern the authorship of the works, for they have often been
used to this end. We should even be tolerant of variable and erratic
spelling, for this was to some extent a common Elizabethan practice."

14) The Friedmans particularly do not insist that the existence of a cipher
be clearly signaled in the open text. In fact they consider it unreasonable
to expect to find signs calling attention to concealed information. They
quote Francis Bacon himself, who wrote "The vertues of cyphars whereby they
are to be preferred are three; that they be not laborious to write and
reade; that they be impossible to decypher; and in some cases, that they be
without suspicion." [steganographic] The Friedmans' view was that "One does
not put something in a secret hiding-place and then put up a sign saying,
`Notice: Secret Hiding-place'."

15) So, they do not "demand any external guide to the presence of the secret
texts." As to the additional probative value of an actual external beacon
and guide, they are silent. Neither do the Friedmans comment upon the
reverse situation, where a reference might be made in the deciphered
information to the open text, or vice-versa.

source: The Second Cryptographic Shakespeare, Penn Leary

Also, I'll take the liberty of posting this fascinating (albeit dense)
article on Friedman and the Beale ciphers:
http://www.myoutbox.net/bch1.htm

Enjoy,

Luis

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