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history of Vernam-Vigenère cipher

Frequency distribution for plaintext and its repeated-key Vigenère cipherThe most frequent plaintext letter is assigned a value of 100 and the remaining plaintext and ciphertext letters are given values from 0 to 100 relative to their frequency of occurrence. Thus, the most frequent letter (1 on the horizontal scale) has a value of 100, while the next most frequent letter (2) has a value of about 78, and so forth. The Vigenère ciphertext has a remarkably less-telling distribution, although not as pronounced as the completely flat random polyalphabetic cipher.
...and intersymbol correlation), on which earlier methods of decryption of different Vigenère systems had relied, could be eliminated if a random series of marks and spaces (a running key) were mingled with the message during encryption to produce what is known as a stream or streaming cipher.
...for transmission. This operation was performed in reverse using a copy of the paper tape at the receiving teletypewriter to decrypt the cipher. Vernam initially believed that a short random key could safely be reused many times, thus justifying the effort to deliver such a large key, but reuse of the key turned out to be vulnerable to attack by methods of the type devised by Friedrich...


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