Native American Encryption?!

[David Koontz]

Navajo (Navaho) Indians.  Referred to as Code Talkers.  I believe you'll
find something in David Kahns "The Code Breakers".  They were used in
tactical situations.

To break an otherwise unknown language would require context, such as
good traffic flow analysis and otherwise good intelligence.  I beleive
there was a program on A&E (TV) on the Navajo code talkers in the Pacific
(WWII).  Navajo code talkers used lots of colloquilisms and all new
each other more or less.  You could have ended up attacking language
code in sets between two code talkers.