“The ? before OBKR as the 98th letter: a full 7 x 14 grid, turned so the ? comes out first, with an autokey or a repeating key”
With the carved ? counted, K4 has 98 symbols, which fill a 7 x 14 grid exactly. Here the message plus a ? somewhere in it is written into a grid of 98 cells and read out from any corner, once or twice, by K3's rule on 98, or by a seven-column shuffle in any of its 5,040 orders; the reading must bring the ? to the front, where it is carved. The 97 letters are then keyed by a repeating key, or by the plaintext or ciphertext autokey, which the padded-grid searches never paired with the 98-cell grid.
On the sculpture a question mark sits just before K4the carved letters The 97 letters cut into the copper at the CIA, shown at the top of every experiment page.. Counted with it, K4 has 98 symbols, and 98 fills a grida grid Writing the message into rows of some width and reading it out in another order, column by column for instance, which shuffles the letters without changing them. of 7 by 14 exactly, the way the third messagethe earlier messages The three solved parts of the sculpture.'s 336 letters filled its grid. Perhaps the question mark was part of the messagethe message The 97 letters of English that Jim Sanborn wrote and enciphered., the grid was turned so that it came out first, and the letters were then keyed. We try every grid and every way of reading it out that puts the question mark in front, with a repeating secret wordthe secret word The word or string a cipher needs besides the method. or an autokeyan autokey cipher A cipher that uses the message itself, or the scrambled text itself, as the secret word, each letter enciphered with the letter a fixed distance before it., and the same on ten scrambled coppers.
Words in the margin are defined on the glossary page.
1.1
The method at work
The carved letters go in at the top; the reading comes out at the bottom.
the grid
Counted with the ? before it, K4 has 98 symbols, which fill seven rows of 14 exactly, the way K3's 336 letters filled its grid.
the move
Read from the right, each column bottom-up, the last cell comes out first: a ? that ends the message is carved in front, as on the sculpture.
the bound
300,651 moves that bring the ? to the front, with a repeating key or an autokey: nothing beyond chance. The 72 three-check settings are 34 distinct sets of checks repeated by look-alike shuffles.
2
Best candidate against the known letters
This experiment produced no candidate: the search ruled everything out before a full text was built. Its product is the bounded negative in section 7.
3
Walkthrough, by hand
Redo the method on a few letters with pencil and paper.
Put a ? at the end of the message: 98 symbols.
Write them in rows of 14: seven full rows, no blank cell.
Read the columns from right to left, each from the bottom up. The first cell read is the last one, the ?, so it is carved first, as on the sculpture.
Place 22, the E of EAST, is in row 1, column 7. Columns 13 to 8 give 42 symbols; column 7 read from the bottom reaches row 1 at its sixth cell, symbol 48, which is carved letter 47 once the ? is set aside.
Key the 97 letters with a repeating key or an autokey; each known letter and the copper letter where it landed tie the key, and the ties must agree.
Repeat for every grid width, reading corner, second grid, K3's rule on 98, every order of seven columns, every key, and ten scrambled coppers.
the worksheet: the first steps by hand, on squared paper
4
Worked example, generated
The same steps run by the code on the real letters.
98 cells in rows of 14 (7 rows, full), read right to left, each column bottom-up: the first cell read is the last one,
so the ? must be the last symbol of the message (q = 97) to be carved first.
? position in the message: 97
place letter row column carved place
22 E 1 7 47 (Z)
23 A 1 8 40 (S)
64 B 4 7 44 (S)
65 E 4 8 37 (W)
74 K 5 3 71 (Z)
5
Hypothesis, for a cryptanalyst
Family, key space, the constraint under test, and the clues it reads.
Type 2 of directions.md, the prior-work database's seven-based sub-variant 2 ('a 7x14 grid of 98 (with ?) under a K3-style rotation plus a non-periodic key (autokey, progressive); padded rotations were tested only with periodic keys', nitsuah). Clues C18(b) (Scheidt 2004-5, 'I think there are 98 characters left'; a 98-character working text including ?), C17(c) (the ? counts), C1(a) and C2(a) (the K3 move; K3's 336 letters fill 24 x 14 and 8 x 42 exactly, so a full grid is Sanborn's habit), and the width-7 doublet column (0056). Model: the 97 plaintext letters with a ? inserted at some symbol position q (98 symbols); a move T on 98 cells; the carved text is ? followed by the 97 letters, so T must send q to position 0, which fixes q for each T. Moves: one grid of width 2-97 (ragged bottom row) read from any of four corners (columns left to right bottom-up, right to left top-down, left to right top-down, right to left bottom-up), forward and inverse; two such grids at every width pair and reading pair, forward and inverse (repeating key only); K3's rule a + b i mod 98 for b prime to 98; seven-column shuffles in all 5,040 orders, forward and inverse. Keys on the 97 letters: periodic tableau key 1-26 after the move (slot = carved letter position mod p), before it (slot = plaintext letter position mod p), or before it with the ? taking a slot (slot = symbol position mod p), 8 classes; plaintext and ciphertext autokey, lags 1-96, one alphabet throughout, three modes, after or before the move (not with two-grid moves at widths that do not divide 98). Exact; ten shuffled coppers (the 97 letters shuffled, the ? kept first).
6
Prediction
Written before the run; the result decides it.
Nothing live below period 22 for the repeating keys beyond the shuffled-copper rate; no autokey setting passes five checks; counts at every level inside the control range, give or take the spread at the lowest levels. Zero candidates.
7
Method
Build every move on 98 cells and find the ? position it brings to the front.
Turn it into a reordering of the 97 letters.
Test a repeating key of length 1-26 in three placements by the forced-letter slots.
For the one-grid moves, full two-grid moves, K3's rule and the seven-column shuffles, test the plaintext and ciphertext autokeys at every lag on either side.
Count survivors on K4 and ten shuffled coppers; list K4's survivors below period 20 or with four or more checks, with the ? position.
8
Result and bounds
The harness's record: candidates, gates, loss, and the negative result this experiment leaves behind.