@Article{Riv81,
  author = 	 { Ronald L. Rivest },
  title = 	 { Statistical analysis of the {Hagelin} cryptograph },
  pages = 	 { 27--32 },
  doi =          { 10.1080/0161-118191855751 },                  
  blocked =      { pdf },                  
  journal = 	 { Cryptologia },
  publisher =    { Taylor \& Francis },                  
  date =         { 1981-01 },                  
  volume = 	 { 5 },
  number =       { 1 },                  
  OPTyear = 	 { 1981 },
  OPTmonth =     { January },                  
  abstract =     {
        We derive here a formula which estimates how much ciphertext is needed
        to solve a cryptogram produced by a Hagelin cryptograph, using the 
        cryptanalytic technique presented by Barker [1].  We shall see that no
        more than 8000 characters of ciphertext are needed to solve a Hagelin
        Model C-48 (or U.S. Army M-209) cryptogram.  The Hagelin cryptograph was
        invented in the 1930's by Boris Hagelin; many thousands of these machines
        were produced in the subsequence decades.                  
                 },
}