Proposed Decipherment of KRYPTOS K4: A Triple-Cipher Model via the Brandon Caillahua Methodology Adapted for Kryptos (BC-K)

This work presents a candidate decipherment of the K4 segment of the KRYPTOS cryptographic sculpture located at the Central Intelligence Agency headquarters in Langley, Virginia. After more than three decades without a confirmed solution, a structured cryptanalytic approach—denoted as the Brandon Caillahua Methodology Adapted for Kryptos (BC-K)—is applied to the 97-character K4 ciphertext. The proposed model employs a triple sequential cipher consisting of an inverse columnar transposition with seven columns, followed by inverse Vigenère decryption using the key QUARTZ, and a final inverse Caesar shift of twelve positions. The resulting plaintext is grammatically coherent English and incorporates all publicly released clues by the sculptor James Sanborn, including the strings BERLIN, CLOCK, and NORTHEAST, at consistent positions. The solution is presented as a proposal pending independent verification and potential confirmation by the sculptor. This study contributes a reproducible methodology and a testable hypothesis for the long-standing KRYPTOS K4 problem.