The Autokey cipher eliminates this repetition. It consists of two parts: a (the pre-shared secret keyword) and the keystream (the primer followed by the plaintext itself).
For the first $N$ characters: $$C_i = (P_i + K_i) \pmod26$$ auto-key crack only
The attacker aligns the crib at various positions in the ciphertext. The Autokey cipher eliminates this repetition
Assume the attacker guesses a probable word in the plaintext (a "crib"). Common cribs in English include "THE", "AND", "TION", or standard headers like "TO THE". or standard headers like "TO THE".