"The CSP-1286 authentication system involves the use of two cards - a top card and a bottom card.

a. TOP CARD: This card is made up of ten rows of twenty-six spaces with a random assortment of letters and spaces - a grill. To the left of each row under the heading of "Hours" are found the row indicators - the alphabet randomly placed with one, two, three, or four letters assigned to each row. Beside these and next the grill itself are the numbers placed in order from one through ten. There is found at the top row of twenty-six spaces for a direct standard alphabet, the letter s placed first being the key letter. At the bottom of the card is a direct standard alphabet starting with the letter "A". Underneath is a row of spaces where the numbers from one through ten may be placed in order starting with the key letter for the day. To the left of this is the row indicator, "Digits".

b. BOTTOM CARD: This card is composed of thirty-five incomplete alphabets with one or two letters omitted and the same number repeated. There are three columns to the left of the order numbers from 00 to 23. In the next column are found the letters of the alphabet in order. The third column is blank. The first incomplete alphabet is found next to the number and letter, 01-B."


"METHOD OF USE: In operation, the top card, or grill, is placed over the bottom card. The first row of random letters of the grill is placed over the incomplete alphabet to the right of the hour just following the hour of the message. The authenticator, which is a three-letter self-authenticator, is found in any one of the ten rows made by the grill placed over the bottom card. The letters of the authenticator are together in succession. They are letters not repeated in the same order in any other place."


The information enclosed here is quoted directly from:
Survey Of Authentication Systems 1942-45 (1945) This is available from NARA; NSA Historical Collections 190/37/7/1, NR 3526 CBRK24 12960A 19420728.
We are seeking more information on this system that will be used to create a clearer description of this system.

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