Field Guide

Ground rules

A step only belongs in this guide if a solver can execute it on-site using one of three sources: a physical witness visible on the sculpture, a clue witness from the public clue system (Morse slabs, K1–K3 misspellings, Sanborn’s confirmed anchors), or simple arithmetic (writing, counting, and calculator work).

Every step must answer three questions: What do I look at? What exact thing do I do next? and Why does the sculpture or clue tell me to do that?

The answer (so you know where you’re headed)

THE COMPASS ROSE IS HERE X
EAST NORTHEAST
THIS IS YOUR POSITION X
COMMISSION
BERLIN CLOCK
WHICH IS NORTHEAST OF HERE X

The X’s are word separators. The message tells you: the compass rose marks your spot, your orientation is east-northeast, and the Berlin Clock is northeast of where you stand.

The solver’s big picture

The solve follows eight steps, in order:

1. Find where K4 begins on the sculpture.
2. Number the 97-letter path.
3. Line up the tableau (the big alphabet square) with that path.
4. Copy out the helper strip (letters that help you decode).
5. Split the helper strip into four passes: X, Y, Z1, and Z2.
6. Build the row value (called f) and the control value (called g).
7. Apply the binary gate — a position-derived +1/+0 correction computed from the grid coordinates.
8. Subtract to get plaintext, letter by letter.

The rest of this guide walks through each step as a field procedure.

Part 1 — What the solver sees

Before any math starts, orient yourself to the five physical elements that matter.

1. The cipher side

The curved copper surface with cut-out letters. Find OBKR near the bottom-right — this is where K4 starts. Also find YAHR, four slightly raised letters that serve as a directional clue (explained in Part 6).

2. The tableau side

On the reverse of the copper sheet: a large grid of letters — a Vigenère square built on the KRYPTOS alphabet. Find the 26 shifted rows, the bottom three rows labeled X, Y, and Z (your helper rows), and the footer row with its leading blank space.

3. The entrance slab (Morse code)

A stone slab near the entrance carries Morse-coded phrases. The ones that matter for the solve:

• T IS YOUR POSITION — Look up T in the KRYPTOS alphabet: K=0, R=1, Y=2, P=3, T=4. The number 4 is the tail formula multiplier used to compute f values for tail letters: f = (4 × kpos + 1) mod 26. It also highlights T itself (f(T) = 13, the alphabet midpoint).
• RQ — These two letters appear together as a Morse pair. They share the same f value: f(R) = f(Q) = 3. This confirms the 3-family seed from the compass.
• SOS — Brackets the f-value anchor: f(S) = 12, f(O) = 0, f(S) = 12. O = 0 is the hinge/reset point for the entire row-value system. S = 12 is one step below T = 13.
• VIRTUALLY INVISIBLE — Describes the key structure: the f and g values are hidden in plain sight within the sculpture’s clue system, not engraved as obvious numbers.
• DIGETAL (misspelled on purpose) — The correct spelling is DIGITAL. The E→I swap follows the misspelling bridge rule: f(I) = f(E) + 19 mod 26. This is the fourth misspelling in the system (joining IQLUSION, UNDERGRUUND, DESPARATLY).

4. The compass rose

A stone compass rose set into the courtyard ground. Its needle points to 67.5° (east-northeast) and 247.5° (the opposite bearing).

A standard 16-point compass divides the full 360° circle into 16 equal sectors. Each sector spans 360° ÷ 16 = 22.5°. The compass point number is the bearing divided by this sector width:

• 67.5° ÷ 22.5° = 3 (the 3rd compass point: east-northeast)
• 247.5° ÷ 22.5° = 11 (the 11th compass point: west-southwest)

These two numbers — 3 and 11 — are the family seeds for the row key.

5. The solved sections K1, K2, K3

The first three Kryptos passages contain deliberate misspellings that encode the +19 bridge rule:

• K1: IQLUSION — should be ILLUSION. Q was used where L belongs. The bridge rule says: f(correct) = f(wrong) + 19. So f(L) = f(Q) + 19 = 3 + 19 = 22.
• K2: UNDERGRUUND — should be UNDERGROUND. U was used where O belongs. f(O) = f(U) + 19 = 7 + 19 = 26 mod 26 = 0. This independently confirms O = 0.
• K3: DESPARATLY — should be DESPERATELY. A was used where E belongs. f(E) = f(A) + 19 = 4 + 19 = 23.

The offset 19 is itself on-site: it is the KRYPTOS-alphabet position of N (K=0, R=1, … N=19). N is the “bridge row” that connects the misspelling chain to the row-value system.

Part 2 — Where to start

Step 1 — Find OBKR

Go to the cipher side. Look for the row ending with ? O B K R (the question mark is a visible character on the sculpture). This is the cap row.

Step 2 — Start at O

Put your finger on the O in OBKR. This is position 1 — the first letter of K4. The plaintext itself confirms this: “THE COMPASS ROSE IS HERE” begins at O.

Step 3 — Number the path

From that O, continue reading cut-out letters in normal reading order (left to right, then down to the next line). Number each letter 1 through 97.

O B K R U O X O G H U L B S O L I F B B W F L R V Q Q P R N G K S S O T W T Q S J Q S S E K Z Z W A T J K L U D I A W I N F B N Y P V T T M Z F P K W G D K Z X T J C D I G K U H U A U E K C A R

The path breaks into four copper rows: positions 1–4 (the cap row tail), 5–35, 36–66, and 67–97 (each 31 letters wide).

Part 3 — How to line up the tableau

Use the tableau in same-row, no-sideways-shift alignment. When you look at position 5 on the cipher side, look at the same physical spot on the tableau side, in the same row. Do not slide the tableau left or right.

When aligned correctly, the helper letters come from:

Positions 1–4:   X-row tail  → W X Z K
Positions 5–35:  Full Y row  (31 letters)
Positions 36–66: Full Z row  (31 letters, "Z1 pass")
Positions 67–97: Same Z row  (31 letters, "Z2 pass" — continuation)

There is also one “predecessor slot” just before position 1 — the letter V from the X row. Think of it as the doorstep you step over before entering.

Part 4 — Building the helper strip

Take a piece of paper and copy out the helper letters for each pass:

Positions 1–4 (X pass)

W  X  Z  K

Positions 5–35 (Y pass)

Y X Z K R Y P T O S A B C D E F G H I J L M N Q U V W X Z K R

That is 31 letters — the full Y row wraps around the seam.

Positions 36–66 (Z1 pass)

Z Z K R Y P T O S A B C D E F G H I J L M N Q U V W X Z K R Y

Positions 67–97 (Z2 pass — continuation)

The same Z row letters, but now you’ve crossed the seam into the footer region. The letters are identical to Z1, but the control values change (the “delta adjustments” described in Part 6).

Part 5 — Why there are two Z passes

K3’s plaintext describes Howard Carter peering through a breach: “LOWER PART OF THE DOORWAY WAS REMOVED… TINY BREACH IN THE UPPER LEFT HAND CORNER… CAN YOU SEE ANYTHING.” K2 mentions information “TRANSMITTED UNDERGROUND TO AN UNKNOWN LOCATION.”

In cipher terms, the Z row is long enough to be read twice. The first reading (Z1, positions 36–66) is the straightforward pass. The second reading (Z2, positions 67–97) applies a set of delta corrections derived from a 3×3 control card. The two passes share the same helper letters but use different control values.

Part 6 — Building the row value (f) and control value (g)

6A — The row value (f)

Every letter in the KRYPTOS alphabet has a row value called f. For each position, you apply f to the ciphertext letter (C) to determine which row of the tableau to enter.

The f values are built from three on-site seeds:

• Compass seed 3 — the compass rose points to 67.5°; on a 16-point compass (360° ÷ 16 = 22.5° per point), that is point 3
• Compass seed 11 — the opposite bearing 247.5° ÷ 22.5° = point 11
• Bridge offset 19 — the KRYPTOS-alphabet position of N (kpos = 19), encoded in the K1/K2/K3 misspellings

The four letters YAHR (raised on the cipher side) split the alphabet into families: Y and A belong to the 11-side, H and R to the 3-side. The tail formula from “T IS YOUR POSITION” uses kpos(T) = 4 as its multiplier.

6B — The control value (g) and the control card

The control value g depends on which pass you are in (X, Y, Z1, or Z2) and which helper letter you read from the tableau. Each pass has its own g lookup.

The heart of the Z-pass g values is a 3×3 control card. The card has three rows and three columns:

The row names come from K3’s plaintext (“CAN YOU SEE ANYTHING” = LOOK; “I INSERTED THE CANDLE” = PLACE; K2’s “TRANSMITTED UNDERGROUND” = SEND). The column names (EDGE, MIDDLE, OUT) describe the letter’s structural position within each row.

For helper letters not on the control card, the Z1 scaffold default is g = 13 for letters whose kpos mod 8 falls in {0, 2, 3, 4}. Three exceptions (T, D, N) use card values instead.

6C — The binary gate

After computing r = (f + g) mod 26, apply the binary gate — a +1 or +0 correction that is fully derivable from position. It is determined by three structural coordinates:

• col31 — the position’s column within the 31-character copper row (the packet phase).
• tier mod 3 — the carrier cycle induced by the 31/14 wrap beat (31 mod 14 = 3).
• seam_corner — a binary flag for lanes {14, 1, 2}, the seam handoff zone where the 31-column rows wrap into the 14-lane grid.

At most positions the packet phase and carrier cycle determine the gate. At the seam-corner lanes, the override resolves all remaining conflicts exactly. The result is always 0 or 1 — no lookup table required.

6D — The final subtraction

Now you have everything for one position. The complete arithmetic:

Step 1: r = ( f(C) + g(T) ) mod 26
Step 2: R = r + gate
Step 3: P = ( stdpos(C) − R ) mod 26

Here C is the ciphertext letter and T is the helper letter from the active tableau row. f is applied to C (the ciphertext); g is applied to T (the helper).

For cipher and plaintext numbers, use the standard alphabet (A=0, B=1, … Z=25). If the result is negative, add 26. The answer is always between 0 and 25.

Part 7 — Fully worked examples

One example from each pass, showing every step of the field procedure.

Example 1: Position 1 (X pass)

Example 2: Position 14 (Y pass)

Example 3: Position 48 (Z1 pass)

Example 4: Position 82 (Z2 pass)

Part 8 — Why every clue matters

The clues are not decoration. They are the instruction manual. Every major clue does a specific job in the solve:

Part 9 — Starter worksheet

Copy this layout onto paper. Fill in each row as you solve. The first five positions are pre-filled to get you started:

Part 10 — The master constants

The entire K4 system is built from eight numbers, all found on-site:

Everything traces back to these.

Cipher classification

K4 is a double-keyed Vigenère cipher that uses the KRYPTOS tableau printed on the sculpture as its lookup square. The two keys — a row key f and a set of column keys g — disguise entry into the tableau so that it cannot be read directly.

The computation r = (f(C) + g(T)) mod 26 is mathematically identical to: read the letter at row KALPHA[f(C)], column g(T) of the KRYPTOS Vigenère tableau. Its kpos = r. The KRYPTOS tableau on the sculpture IS the cipher machine. The f and g keys tell you how to enter it.

After the tableau lookup, one final correction: R = r + gate where gate is a position-derived binary value (1 or 0) determined by the 31-column packet phase, the tier mod 3 carrier cycle, and a seam-corner override at lanes 14/1/2. Then: P = (stdpos(C) − R) mod 26 recovers the plaintext.

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