K4 Solution

The plaintext

Below is the complete K4 plaintext in two forms: a lineated reading version and the continuous cipher-output string. Both represent the same 97 characters. Artist-confirmed anchors (EAST, NORTHEAST, BERLIN, CLOCK) appear at their documented positions. All other characters are produced by the same closed mechanism.

Inscription layout (for reading)

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

Continuous string (fidelity reference)

THECOMPASSROSEISHEREXEASTNORTHEASTTHISISYOURPOSITIONXCOMMISSIONBERLINCLOCKWHICHISNORTHEASTOFHEREX

Line breaks in the inscription layout are editorial, they aid readability. The continuous string is the fidelity reference. X functions as a separator/null marker, consistent with Kryptos conventions.

Word-by-word position map

Every word in the plaintext maps to specific positions in the 97-character stream. The table below shows each phrase, its position range, the corresponding ciphertext, and its location on the 7×14 grid.

✓ = artist-confirmed anchor. Tier = row in the 7×14 grid (each tier spans 14 positions).

What the plaintext says

The K4 plaintext reads as a set of navigational instructions anchored to the Kryptos installation itself. Each phrase carries specific physical meaning:

THE COMPASS ROSE IS HERE. The sculpture's compass rose, carved into the courtyard ground, marks the reference point. "Here" is literal: the physical location where you stand.

EAST NORTHEAST, A directional bearing from that reference point. East-northeast (approximately 67.5° from north) establishes the orientation the message is pointing toward.

THIS IS YOUR POSITION, The viewer's location matters. Position is not metaphorical, it is the central variable of the entire cipher mechanism. Every shift value in the 7×14 grid is determined by your position in the stream.

COMMISSION, Likely references the CIA commission that produced Kryptos, or the act of commissioning a message to be sent. Sanborn has stated Kryptos is fundamentally about "delivering a message."

BERLIN CLOCK, References a clock in Berlin. Sanborn confirmed "BERLINCLOCK" at positions 64–74 and in November 2025 clarified that the intended referent is the Weltzeituhr (World Clock) at Alexanderplatz, a world time clock that sits on a compass-rose mosaic, not the Mengenlehreuhr (Set Theory Clock) as the community had assumed for 11 years.

WHICH IS NORTHEAST OF HERE, Berlin is geographically northeast of CIA headquarters in Langley, Virginia, at a bearing of approximately 44° from north. The message confirms the directional relationship between the sculpture and its Berlin referent.

Sanborn has stated that K4's plaintext is itself "a riddle" that will "lead to something else", a reference to the announced K5, a new 97-character coded message thematically connected to K2.

The four confirmed anchors

Jim Sanborn publicly confirmed four K4 plaintext segments over a span of ten years. All four are preserved at their exact documented positions in this solution.

The combined known plaintext at positions 22–34 reads EASTNORTHEAST. At positions 64–74 it reads BERLINCLOCK. Both fragments align with the navigational instruction reading of the full plaintext.

How the cipher works (simplified)

K4 is a Quagmire III variant with a physical keystream and a one-bit gate. The keyword is KRYPTOS, the same one used for K1, K2, and K3. The keystream is the tableau side of the copper screen: for each K4 ciphertext position, the helper letter is the character on the back of the sculpture at the same row and column. For each of the 97 positions:

r = ( f(C) + g_state(T) ) mod 26
R = r + gate
P = ( stdpos(C) − R ) mod 26

C is the ciphertext letter (A=0, B=1, … Z=25). T is the helper letter read physically off the tableau side of the sculpture at the same row and column. f(C) is the row-identity card, it tells you which row of the KRYPTOS-keyed tableau the cipher letter belongs to. g_state(T) is the column offset from standard Quagmire III lookup; one of four helper cards (g_X, g_Y, g_Z1, g_Z2), selected by which of the four 31-cell passes the position belongs to. The gate is a one-bit adjustment (0 or 1) fixed by the position, fully solved, and fully verifiable (see the note on the How It Works page). The final subtraction produces the plaintext letter P.

Every value in the f-table and every helper-card value is forward-derivable from public clues and the physical sculpture. No fitting, no external chart, no hidden key. See the Field Guide for the four-step on-site procedure, or the verification page for the full helper-card derivations.

Worked example: Positions 1–5

Here are the first five positions of K4, computed step by step:

Reading the plaintext column: T, H, E, C, O, the first five letters of "THECOMPASS..." Every position in the cipher resolves the same way. The full 97-position reconciliation table is available on the verification page.

The 7×14 shift grid

The 97 characters of K4 map to a grid of 7 tiers (rows) and 14 lanes (columns), a total of 98 cells, with one blank at Tier 7, Lane 13. Each cell holds an R value (the shift applied at that position). The grid coordinates are computed from the stream position:

lane = ((i − 2) mod 14) + 1
tier = ⌈i / 14⌉

For the complete R-grid and r-grid tables, worked examples at every tier, and the gate map, see How It Works. For the full 97-row reconciliation table, see Verify It Yourself.

Cipher classification

K4 is a Quagmire III variant, a keyword Vigenère with a separate column key, using the KRYPTOS-keyed tableau printed on the sculpture as its lookup square. The keyword is KRYPTOS (shared with K1–K3). The keystream comes from the tableau side of the copper screen: at each K4 ciphertext position, the helper letter is the character on the back of the sculpture at the same row and column. A one-bit gate (fixed by position) adjusts the final shift. The sculpture itself is the key.

The decryption formula: r = (f(C) + g_state(T)) mod 26, then R = r + gate (a one-bit value fixed by position), then P = (stdpos(C) − R) mod 26. The four passes are X (positions 1–4), Y (5–35), Z1 (36–66), and Z2 (67–97), each with its own helper card derived from the back-side letters in that pass. For Z2, the visible footer is standard alphabet text, but the lookup basis is converted into KALPHA state before the helper-card value is read.

A small set of master constants recurs throughout the derivation, all sourced from on-site artifacts: 4 (tail multiplier from the T clue), 13 (scaffold default), 19 (bridge offset from K1/K2/K3 misspellings), 3 and 11 (compass seeds), and 24 (seam base). See the Field Guide for the four-step on-site procedure or the verification page for the full helper-card layer.

How every clue maps to a solve step

Sanborn's clues are not decoration. Every one performs a specific function in the on-site decryption procedure:

What remains

The cipher mechanism is fully closed. The plaintext, the Quagmire III decoder, the physical helper keystream, the gate, and every helper-card value are known and verified at 97/97 positions. The formula r = (f(C) + g_state(T)) mod 26 derives every base shift from the ciphertext letter, the helper letter read from the back of the sculpture, and the helper card selected by which of the four 31-cell passes the position belongs to. No external chart, no hidden key, no algorithmic second layer is required, the second layer is the literal back of the copper screen, exactly as Sanborn's 2006 K2 correction ("X LAYER TWO") said.

What remains is artist confirmation of the complete encryption method. Sanborn has confirmed four plaintext anchors but has not publicly released the coding procedure. The mechanism documented here is independently derived and awaits formal confirmation from the artist or from the sealed Smithsonian records (embargoed until 2075).

Sanborn has announced K5, a new 97-character coded message to be released publicly when K4 is cryptographically solved.

Continue

Frequently asked questions

What is the K4 plaintext?

THE COMPASS ROSE IS HERE X EAST NORTHEAST THIS IS YOUR POSITION X COMMISSION BERLIN CLOCK WHICH IS NORTHEAST OF HERE X, a 97-character navigational instruction anchored to the Kryptos courtyard installation, pointing toward the Berlin Clock (Weltzeituhr at Alexanderplatz).

How was K4 solved?

Through structural cryptanalysis working outward from the four artist-confirmed anchors (EAST, NORTHEAST, BERLIN, CLOCK), and a key discovery: the cipher's helper keystream is physically present on the back of the sculpture. For each K4 ciphertext position, the helper letter is the character on the tableau side at the same row and column. A one-bit gate (fixed by position) adjusts the shift. Standard Quagmire III subtraction produces the plaintext at every position.

Why didn't anyone solve K4 before?

Every prior attempt searched for a keyword for the keystream, a word or phrase like PALIMPSEST or ABSCISSA from K1 and K2. The keystream isn't a word. It's the back of the sculpture itself: a 97-character physical sequence made of the cap WXZK, the full Y row, the full Z row, and a standard alphabet footer that hands off into the Z2 KALPHA-state basis. Sanborn's 2006 correction to K2, replacing the slipped ending "ID BY ROWS" with "X LAYER TWO," was the literal hint: there are two physical layers, and the K4 mechanism requires reading both.

Is K4 officially confirmed?

The four anchor words are confirmed by the artist. The full 97-character plaintext was independently recovered from Sanborn's Smithsonian archives in September 2025 by Jarett Kobek and Richard Byrne and was not publicly disclosed. In December of 2025, the plaintext solution was independently derived by the author of this site. Sanborn has not publicly released the full text or the encryption method.

What does the K4 plaintext mean?

It reads as a site-specific navigational instruction: the compass rose at CIA headquarters is the reference point; east-northeast is the bearing; Berlin (specifically the Weltzeituhr at Alexanderplatz) is the destination. Sanborn has stated the plaintext is itself "a riddle" leading to K5, a new coded message connected to K2.

What is the Berlin Clock reference?

Sanborn confirmed "BERLINCLOCK" at positions 64–74. For 11 years the community assumed this meant the Mengenlehreuhr (Set Theory Clock). In November 2025, Sanborn clarified the intended referent is the Weltzeituhr (World Clock) at Alexanderplatz, a world time display that sits on a compass-rose mosaic, mirroring Kryptos's own compass rose.

What would falsify this solution?

Confirmation of any plaintext letter inconsistent with the full 97-character string at its verified position, or release of Sanborn's original coding records showing R-values or r-values that contradict the published reconciliation table. The mechanism is falsifiable by design: every claim is position-indexed and arithmetically checkable.

What does OBKR mean in Kryptos?

OBKR are the first four ciphertext characters of K4. They occupy the capstone alignment row, the rightmost four columns of the last row shared with K1–K3 on the copper screen. Under the solution documented here, OBKR decrypts to THEC (the start of “THE COMPASS ROSE IS HERE”). The letters themselves are not an acronym; they are the encrypted form of the plaintext at positions 1–4. On the tableau side at the same row and columns, OBKR aligns with WXZK, the active X-pass cap of the helper keystream.

Who solved Kryptos K4?

The K4 plaintext was independently recovered from Jim Sanborn's Smithsonian archives in September 2025 by journalist Jarett Kobek and artist Richard Byrne, though they emphasized this was not a cryptographic solution. The complete cryptographic mechanism (Quagmire III decoder, physical helper keystream, one-bit gate, and shift tables) was independently derived and documented by Matt Lacy in December 2025. K1–K3 were solved by CIA analyst David Stein (1998, classified) and cryptographer Jim Gillogly (1999, public).