Substitution

Methods that replace each letter with a different letter using a key or pattern, like a secret alphabet. Includes Vigenère, Beaufort, Quagmire, Hill, and more.

What we tested: Every repeating key 1 to 26 letters long has been ruled out for K4 as carved (each ciphertext letter hiding the plaintext letter in the same position) under Vigenère, Beaufort and Variant Beaufort, on both the ordinary A to Z alphabet and the sculpture's KRYPTOS alphabet: not just searched, but ruled out directly from the known plaintext. With any keyword-mixed alphabet used the way K1 and K2 use the KRYPTOS alphabet (the same mixed alphabet for plaintext and ciphertext), keys of 1 to 22, 24 and 25 letters are ruled out the same way. Versions that use two different mixed alphabets, and Gromark ciphers with mixed alphabets on both sides, are not fully ruled out. A repeating key combined with a letter-rearrangement step is a separate question (see Multi Layer).

80 eliminations recorded.

Title	Configs	Best	Verdict	Tier
Physical strip cipher model from Sanborn oral history Tested analysis of the internal key values the cipher would need to produce. 86.5 million key/parameter combinations were tested.	86,502,054	N/A	NOISE	N/A
Hill cipher with YAR-derived matrix parameters (width 9) Every width-9 column order with any 2x2 Hill matrix (both layer orders) or any 3x3 Hill matrix (one layer order only), using a method that encrypts gr…	43,282,720	N/A	ELIMINATED	Tier 2
Beaufort-focused K4 attack Tested a method that replaces each letter using a repeating keyword with reversed arithmetic (Beaufort cipher). 25.1 million key/parameter combination…	25,068,142	8/24	NOISE	N/A
Cipher Model Deep Structural Tested analysis of the internal key values the cipher would need to produce. 11.9 million key/parameter combinations were tested. Best match: 15/24 kn…	11,886,547	15/24	NOISE	N/A
Keystream generated by columnar transposition of periodic key Tested a method that replaces each letter using a repeating keyword (Vigenère cipher). 9.8 million key/parameter combinations were tested.	9,818,640	N/A	NOISE	N/A
Cysquare cipher on Kryptos Vigenere tableau (26x26 body) Tested a method that replaces each letter using a repeating keyword (Vigenère cipher). 2.3 million key/parameter combinations were tested.	2,339,030	8/24	NOISE	N/A
VIC key derivation + Beaufort/Vigenere substitution hybrid (no checkerboard) Tested a method that replaces each letter using a repeating keyword (Vigenère cipher). 255 thousand key/parameter combinations were tested.	254,720	6/24	NOISE	N/A
NDYAHR directional vectors coupled with consensus null mask + col-7 Beaufort Tested a method that replaces each letter using a repeating keyword with reversed arithmetic (Beaufort cipher). 64 thousand key/parameter combinations…	63,684	7/24	NOISE	N/A
K0 Morse text (10+ variants) as running key for K4, all offsets, Beaufort/Vigenere/VarBeau, AZ/KA, Model A... CT97) + Model B (CT73), using a method that replaces each letter using a repeating keyword (Vigenère cipher). 28 thousand key/parameter combinations w…	28,140	5/24	NOISE	N/A
Keyword-derived transposition reveals periodic key Tested a method that replaces each letter using a repeating keyword (Vigenère cipher). 12 thousand key/parameter combinations were tested. Best match:…	11,684	17/24	NOISE	N/A
Screen of CIA cryptonym-style words (formation rule documented from Sanborn's own worksheet photographs) as... Candidate plaintext or key fragments, across additive and Quagmire III convention cells including key phases and gap regions, using a method that uses…	5,040	N/A	NOISE	N/A
Cipher Model Crosssweep Tested analysis of the internal key values the cipher would need to produce. 2 thousand key/parameter combinations were tested. Best match: 15/24 know…	1,872	15/24	NOISE	N/A
Cipher Model Variations Tested analysis of the internal key values the cipher would need to produce. 969 key/parameter combinations were tested. Best match: 15/24 known lette…	969	15/24	NOISE	N/A
Quagmire III tableau-keyword axis completion: diagonal ct==pt tableau variants the earlier DSL could not sw... Eep, under direct and post-transposition alignment, using a method that uses a scrambled alphabet with a repeating keyword (Quagmire cipher). 450 key/…	450	6/24	ELIMINATED	N/A
Cipher Model Variations Ext Tested analysis of the internal key values the cipher would need to produce. 421 key/parameter combinations were tested. Best match: 15/24 known lette…	421	15/24	NOISE	N/A
Z3 SMT proof of periodic key feasibility under Bean+crib constraints Tested a method that replaces each letter using a repeating keyword (Vigenère cipher). 82 key/parameter combinations were tested.	82	N/A	NOISE	N/A
Autokey Vigenere bidirectional back-derivation from BERLINCLOCK Tested a method that replaces each letter using a repeating keyword (Vigenère cipher). 45 key/parameter combinations were tested.	45	N/A	NOISE	N/A
Hill cipher, direct Tests invertible Hill cipher, n=2 and n=3, and powered n=4 at phases 1 and 2, applied directly to the carved text, with the known plaintext at its car…	28	N/A	ELIMINATED	Tier 2
Affine Hill cipher n=3 and n=4, all phases Tests affine Hill cipher n=3 and n=4 at all phases, applied directly, with the known plaintext at its carved positions. Every setting in scope was tes…	28	N/A	ELIMINATED	Tier 2
Affine Hill cipher, direct Tests affine Hill cipher, n=2 and n=3, with powered cells, applied directly to the carved text, with the known plaintext at its carved positions. Ever…	18	N/A	ELIMINATED	Tier 2
Hill cipher n=4, phases 0 and 3 Tests Hill cipher n=4 at phases 0 and 3, applied directly, with the known plaintext at its carved positions. Every setting in scope was tested, and no…	8	N/A	ELIMINATED	Tier 2
Date-derived key '04111922' (Carter tomb EU format) as vigenere Tested a method that replaces each letter using a repeating keyword (Vigenère cipher).	N/A	2/24	NOISE	N/A
Date-derived key '02161923' (Burial chamber opened) as vigenere Tested a method that replaces each letter using a repeating keyword (Vigenère cipher).	N/A	2/24	NOISE	N/A
Date-derived key '11041922' (Carter tomb discovery date) as vigenere Tested a method that replaces each letter using a repeating keyword (Vigenère cipher).	N/A	1/24	NOISE	N/A
Coordinate-style key '3817N7709W' as vigenere (labelled CIA HQ, but HQ is near 38°57′N, not 38°17′N) The key tested was the string '3817N7709W', using a method that replaces each letter using a repeating keyword (Vigenère cipher).	N/A	N/A	NOISE	N/A
Coordinate key '385709N0770706W' as vigenere (close to, not exactly, K2's 38°57′6.5″N 77°8′44″W) The key tested was the string '385709N0770706W', using a method that replaces each letter using a repeating keyword (Vigenère cipher).	N/A	N/A	NOISE	N/A
Date-derived key '1990' (Kryptos installation year) as vigenere Tested a method that replaces each letter using a repeating keyword (Vigenère cipher).	N/A	N/A	NOISE	N/A
Date-derived key '11031990' (Kryptos dedication Nov 3 1990) as vigenere Tested a method that replaces each letter using a repeating keyword (Vigenère cipher).	N/A	N/A	NOISE	N/A
Coordinates as fractional key values 'The point' = decimal point: coordinates as fractional key values, using a method that replaces each letter using a repeating keyword (Vigenère cipher…	N/A	N/A	NOISE	N/A
Vigenere with REVERSED Kryptos-keyed alphabet Tested a method that replaces each letter using a repeating keyword (Vigenère cipher).	N/A	N/A	NOISE	N/A
Repeating-key tests on K4 (repeated letter groups, letter-frequency checks and 23 keywords) Classic tests for a repeating key (repeated letter groups, and letter-frequency checks at every key length from 1 to 30), plus 23 keywords tried as re…	N/A	4/24	NOISE	N/A
Polyalphabetic analysis (E-POLY-01) Tested a method that replaces each letter using a repeating keyword (Vigenère cipher).	N/A	N/A	ELIMINATED	N/A
Running-key Vigenère/Beaufort from novel/speech text Tested a method that replaces each letter using a repeating keyword (Vigenère cipher).	N/A	7/24	NOISE	N/A
Date-derived key '04111922' (Carter tomb EU format) as beaufort Tested a method that replaces each letter using a repeating keyword with reversed arithmetic (Beaufort cipher).	N/A	2/24	NOISE	N/A
Date-derived key '02161923' (Burial chamber opened) as beaufort Tested a method that replaces each letter using a repeating keyword with reversed arithmetic (Beaufort cipher).	N/A	2/24	NOISE	N/A
Date-derived key '02161923' (Burial chamber opened) as var_beaufort Tested a method that replaces each letter using a repeating keyword with reversed arithmetic (Beaufort cipher).	N/A	2/24	NOISE	N/A
Date-derived key '11041922' (Carter tomb discovery date) as beaufort Tested a method that replaces each letter using a repeating keyword with reversed arithmetic (Beaufort cipher).	N/A	1/24	NOISE	N/A
Date-derived key '11041922' (Carter tomb discovery date) as var_beaufort Tested a method that replaces each letter using a repeating keyword with reversed arithmetic (Beaufort cipher).	N/A	1/24	NOISE	N/A
Date-derived key '04111922' (Carter tomb EU format) as var_beaufort Tested a method that replaces each letter using a repeating keyword with reversed arithmetic (Beaufort cipher).	N/A	1/24	NOISE	N/A
Date-derived key '1990' (Kryptos installation year) as beaufort Tested a method that replaces each letter using a repeating keyword with reversed arithmetic (Beaufort cipher).	N/A	1/24	NOISE	N/A
Date-derived key '11031990' (Kryptos dedication Nov 3 1990) as beaufort Tested a method that replaces each letter using a repeating keyword with reversed arithmetic (Beaufort cipher).	N/A	1/24	NOISE	N/A
Date-derived key '11031990' (Kryptos dedication Nov 3 1990) as var_beaufort Tested a method that replaces each letter using a repeating keyword with reversed arithmetic (Beaufort cipher).	N/A	1/24	NOISE	N/A
Coordinate-style key '3817N7709W' as beaufort (labelled CIA HQ, but HQ is near 38°57′N, not 38°17′N) The key tested was the string '3817N7709W', using a method that replaces each letter using a repeating keyword with reversed arithmetic (Beaufort ciph…	N/A	N/A	NOISE	N/A
Coordinate-style key '3817N7709W' as var_beaufort (labelled CIA HQ, but HQ is near 38°57′N, not 38°17′N) The key tested was the string '3817N7709W', using a method that replaces each letter using a repeating keyword with reversed arithmetic (Beaufort ciph…	N/A	N/A	NOISE	N/A
Coordinate key '385709N0770706W' as beaufort (close to, not exactly, K2's 38°57′6.5″N 77°8′44″W) The key tested was the string '385709N0770706W', using a method that replaces each letter using a repeating keyword with reversed arithmetic (Beaufort…	N/A	N/A	NOISE	N/A
Coordinate key '385709N0770706W' as var_beaufort (close to, not exactly, K2's 38°57′6.5″N 77°8′44″W) The key tested was the string '385709N0770706W', using a method that replaces each letter using a repeating keyword with reversed arithmetic (Beaufort…	N/A	N/A	NOISE	N/A
Date-derived key '1990' (Kryptos installation year) as var_beaufort Tested a method that replaces each letter using a repeating keyword with reversed arithmetic (Beaufort cipher).	N/A	N/A	NOISE	N/A
Constrained keystream MCMC with SA for 73-char Beaufort Tested a method that replaces each letter using a repeating keyword with reversed arithmetic (Beaufort cipher).	N/A	N/A	NOISE	N/A
Ct Mutation Nullmask Beaufort Tested a method that replaces each letter using a repeating keyword with reversed arithmetic (Beaufort cipher). Best match: 16/24 known letters, a lev…	N/A	16/24	NOISE	N/A
Polybius grid walk analysis of Beaufort keystream Tested a method that replaces each letter using a repeating keyword with reversed arithmetic (Beaufort cipher).	N/A	N/A	NOISE	N/A
Brute-force PT[34]-PT[35] under Beaufort A=0, scoring extended keystream against confirmed properties Tested a method that replaces each letter using a repeating keyword with reversed arithmetic (Beaufort cipher).	N/A	N/A	NOISE	N/A
Sanborn Error Beaufort Sensitivity Tested a method that replaces each letter using a repeating keyword with reversed arithmetic (Beaufort cipher).	N/A	6/24	NOISE	N/A
Seethrough Beaufort Ka Columnar 01 Tested a method that replaces each letter using a repeating keyword with reversed arithmetic (Beaufort cipher).	N/A	N/A	NOISE	N/A
Periodic Beaufort Keyword Sweep 73char Tested a method that replaces each letter using a repeating keyword with reversed arithmetic (Beaufort cipher).	N/A	N/A	NOISE	N/A
Null Beaufort Exhaustive Tested a method that replaces each letter using a repeating keyword with reversed arithmetic (Beaufort cipher).	N/A	N/A	NOISE	N/A
Null Mask Beaufort Deep 20260404 Tested a method that replaces each letter using a repeating keyword with reversed arithmetic (Beaufort cipher).	N/A	N/A	NOISE	N/A
Period13 Mixed Alphabet Beaufort Tested a method that replaces each letter using a repeating keyword with reversed arithmetic (Beaufort cipher).	N/A	N/A	NOISE	N/A
Agent K4 Keystream Language Scan Tested analysis of the internal key values the cipher would need to produce.	N/A	N/A	NOISE	N/A
BCL Palette Keystream Tested analysis of the internal key values the cipher would need to produce.	N/A	N/A	NOISE	N/A
Bean Keystream Tested analysis of the internal key values the cipher would need to produce.	N/A	3/24	NOISE	N/A
Digraph Anchored Search Tested analysis of the internal key values the cipher would need to produce.	N/A	N/A	NOISE	N/A
Digraph Constrained SA Tested analysis of the internal key values the cipher would need to produce.	N/A	N/A	NOISE	N/A
Digraph Running Key Tested analysis of the internal key values the cipher would need to produce.	N/A	N/A	NOISE	N/A
Keystream structure analysis for width-7 orderings Tested analysis of the internal key values the cipher would need to produce.	N/A	N/A	NOISE	N/A
Monoalphabetic affine cipher exhaustive disproof Tested a simple letter-shifting method (Caesar/ROT cipher or affine substitution).	N/A	5/24	ELIMINATED	N/A
Homophonic substitution applied directly to the carved text (proof of impossibility) A homophonic cipher lets each plaintext letter be written with several different letters, but each carved letter must still stand for just one plainte…	N/A	N/A	ELIMINATED	Tier 1
Nomenclator (code plus cipher) with one fixed code group per word (proof of impossibility) A nomenclator replaces whole words (or letters) with fixed code groups. The word EAST appears twice in the known plaintext but is carved differently e…	N/A	N/A	ELIMINATED	Tier 1
Simple monoalphabetic substitution cipher Tested a method that replaces each letter with a fixed substitute (simple substitution).	N/A	N/A	NOISE	N/A
Cold-start variant of the joint detector go/no-go for monoalphabetic + transposition + running-key composit... Tested a method that replaces each letter with a fixed substitute (simple substitution).	N/A	N/A	NOISE	N/A
Definitive go/no-go test of whether any positional detector can recover a monoalphabetic + transposition +... Running-key composition at K4's text length, using a method that replaces each letter with a fixed substitute (simple substitution).	N/A	N/A	INCONCLUSIVE	N/A
Monoalphabetic-invariant detector built to find running-key structure that survives an unknown substitution... Layer, using a method that replaces each letter with a fixed substitute (simple substitution).	N/A	N/A	INCONCLUSIVE	N/A
Crib 38 Omission Quagmire Search Tested a method that uses a scrambled alphabet with a repeating keyword (Quagmire cipher).	N/A	N/A	NOISE	N/A
Masked Quagmire Iii Probe 2026 05 Tested a method that uses a scrambled alphabet with a repeating keyword (Quagmire cipher).	N/A	N/A	NOISE	N/A
Quagmire3 Exact Sweep Tested a method that uses a scrambled alphabet with a repeating keyword (Quagmire cipher).	N/A	N/A	NOISE	N/A
KA tableau gaps: Porta periods 15-26 (id+columnar all periods), Gronsfeld+columnar, structural proofs (two-... Square/four-square), using a method that uses 13 paired-letter alphabets selected by a keyword (Porta cipher).	N/A	N/A	NOISE	N/A
Null palette {B,G,I,K,O,W,Z} as 7-digit Gromark primer on raw CT97 Tested a method that generates key numbers using Fibonacci-like sequences (Gromark/Vimark cipher).	N/A	N/A	ELIMINATED	N/A
Hill cipher n=2,3 + columnar transposition widths 5-8 Tested a method that encrypts groups of letters using matrix multiplication (Hill cipher).	N/A	N/A	ELIMINATED	N/A
Hill cipher + anomaly-inspired parameters Tested a method that encrypts groups of letters using matrix multiplication (Hill cipher).	N/A	N/A	NOISE	N/A
Exhaustive Gronsfeld (digit-only key) at period 7 Tested a method that uses a numeric key (digits only) to shift letters (Gronsfeld cipher).	N/A	N/A	NOISE	N/A
Mixed alphabet cipher + columnar transposition Tested a method using a scrambled alphabet for substitution.	N/A	N/A	NOISE	N/A