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In article <18919@ucbvax.BERKELEY.EDU> jmm@miro.Berkeley.EDU (James Moore) writes:
> 
> Is knowing the original language of an encrypted message ever necessary
> for attempting to decipher it?

It certainly is; for example, suppose you have a substitution cipher and
you want to do a frequency analysis to find the most common letters. 
Which plaintext letters are most common varies from language to language.

				-- Scott

In article <18919@ucbvax.BERKELEY.EDU> jmm@miro.Berkeley.EDU (James Moore) writes:
>Is knowing the original language of an encrypted message ever necessary
>for attempting to decipher it?

There are some systems for which one is likely to produce the correct
plaintext without necessarily understanding it, but this is not a
universal property of cryptosystems.

Often one can reduce the message to a simple substitution without
knowing what the language is.  Going from there to plaintext generally
requires some information about general characteristics of a language,
although the analyst need not be highly proficient in it.

I recall decrypting some messages in a simulation (part of a cryppy
training exercise) that were in English but kept mentioning the
"BANDITHUTH".  Took me a while to realize that this was the bandit,
Huth.  (Spaces are often omitted in field systems.)  Nonetheless I
had correctly decrypted it without understanding what it meant.

In article <18924@ucbvax.BERKELEY.EDU>, rotondo@ernie.Berkeley.EDU (Scott Rotondo) writes:
< In article <18919@ucbvax.BERKELEY.EDU> jmm@miro.Berkeley.EDU (James Moore) writes:
< < Is knowing the original language of an encrypted message ever necessary
< < for attempting to decipher it?
< 
< It certainly is; for example, suppose you have a substitution cipher and
< you want to do a frequency analysis to find the most common letters. 
< Which plaintext letters are most common varies from language to language.

A code attack which had to guess the language would be harder (N cracking
attempts presuming N different languages, N large and finite) but definitely
not impossible.  Perhaps the N-attempt requirement would put a cracking
attempt beyond practical feasibility if the code was already tough, however.
(Does this make any sense or am I just talking through my hat?)
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