The Fated Sky: A Lady Astronaut Novel, Chapter 16 cypher text.

TheFatedSky.rb

PLAINTEXT = %w(A B C D E F G H I J K L M N O P Q R S T U V W X Y Z)
CRYPTTEXT = %w(E L P H A N T B C D F G I J K M O Q R S U V W X Y Z)

input = "Cj qarmkjra sk ykuq gers gassaq, C ei waeqcjt iy ngctbs rucs lus hk jks beva e lqe kj. Cn yku waqa baqa, C wkugh sefa yku cjsk sba teqhaj ikhuga ejh gaej kvaq sba skiesk lahr rk sbes er yku skkf ia nqki labcjh, iy nepa wkugh la mqarrah cjsk sba nqetqejs tqaaj gaevar wcsb aepb sbqurs.".upcase

input.split("").each do |character|
  if position = CRYPTTEXT.find_index(character)
    print PLAINTEXT[position]
  else
    print character
  end
end and puts 

Oh my!