Gilbert S. Vernam

American engineer

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July 14, 2026

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Gilbert S. Vernam was an American engineer who made a significant contribution to cryptography. In 1918, he devised the Vernam-Vigenère cipher, a type of substitution cipher used for data encryption. This cipher was an important variant of the Vigenère cipher.1

Vernam's innovation involved using a random key stream, similar to a running key, to encrypt messages transmitted over teleprinter systems. This method aimed to eliminate patterns that could be exploited by cryptanalytic attacks. While Vernam's initial idea of reusing a short key was found to be vulnerable, his work laid groundwork for understanding secure communication methods, particularly the concept of a one-time key for unconditional security, later explored by Claude Shannon.1

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cryptology
Vernam-Vigenère ciphers
In 1918 Gilbert S. Vernam, an engineer for the American Telephone & Telegraph Company (AT&T), introduced the most important key variant to the Vigenère system. At that time all messages transmitted over AT&T’s teleprinter system were encoded in the Baudot Code, a binary code in which a…
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In 1918 Gilbert S. Vernam, an engineer for the American Telephone & Telegraph Company (AT&T), introduced the most important key variant to the Vigenère system. At that time all messages transmitted over AT&T’s teleprinter system were encoded in the Baudot Code, a binary code in which a…
Read More

Vernam-Vigenère cipher
…was devised in 1918 by Gilbert S. Vernam, an engineer for the American Telephone & Telegraph Company (AT&T), who introduced the most important key variant to the Vigenère cipher system, which was attributed to the 16th-century French cryptographer Blaise de Vigenère.
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…was devised in 1918 by Gilbert S. Vernam, an engineer for the American Telephone & Telegraph Company (AT&T), who introduced the most important key variant to the Vigenère cipher system, which was attributed to the 16th-century French cryptographer Blaise de Vigenère.
Read More