Gilbert Sandford Vernam (1890–7 February 1960) was a AT&T Bell Labs engineer who, in 1917, invented the stream cipher and later co-invented the one-time pad cipher. Vernam proposed a teletype cipher in which a previously-prepared key, kept on paper tape, is combined character by character with the plaintext message to produce the cyphertext. To decipher the ciphertext, the same key would be again combined character by character, producing the plaintext. 1890 (MDCCCXC) was a common year starting on Wednesday (see link for calendar) of the Gregorian calendar (or a common year starting on Friday of the Julian calendar). ... February 7 is the 38th day of the year in the Gregorian Calendar. ... 1960 (MCMLX) was a leap year starting on Friday (the link is to a full 1960 calendar). ... AT&T Inc. ... Bell Laboratories (also known as Bell Labs and formerly known as AT&T Bell Laboratories and Bell Telephone Laboratories) was the main research and development arm of the United States Bell System. ... 1917 (MCMXVII) was a common year starting on Monday of the Gregorian calendar (see link for calendar) or a common year starting on Tuesday of the 13-day slower Julian calendar. ... The operation of A5/1, a LFSR-based stream cipher used to encrypt mobile phone conversations. ... Excerpt from a one-time pad. ... This article is about algorithms for encryption and decryption. ... A teleprinter (teletypewriter, teletype or TTY) is a now largely obsolete electro-mechanical typewriter which can be used to communicate typed messages from point to point through a simple electrical communications channel, often just a pair of wires. ... A key is a piece of information that controls the operation of a cryptography algorithm. ... A roll of punched tape Punched tape is an old-fashioned form of data storage, consisting of a long strip of paper in which holes are punched to store data. ... The plain text term has a different meaning. ... This article is about algorithms for encryption and decryption. ... The plain text term has a different meaning. ...

Vernam's patent

Figure 1 from Vernam's patent.

The combining function Vernam specified in U.S. Patent 1310719, issued July 22, 1919, is the XOR operation, applied to the individual impulses or bits used to encode the characters in the Baudot teletype code. Vernam did not use the term "XOR" in the patent, but he implemented that operation in relay logic. In the example Vernam gave, the plaintext is A, encoded as "++---" in Baudot, and the key character is B, encoded as "+--++". The resulting ciphertext will be "-+-++", which encodes a G. Combining the G with the key character B at the receiving end produces "++---", which is the original plaintext A. The NSA has called this patent "one of the most important in the history of cryptography."^{[citation needed]} Image File history File links Download high resolution version (443x634, 57 KB)Vernam cipher patent, Figure 1. ... Image File history File links Download high resolution version (443x634, 57 KB)Vernam cipher patent, Figure 1. ... July 22 is the 203rd day (204th in leap years) of the year in the Gregorian Calendar, with 162 days remaining. ... 1919 (MCMXIX) was a common year starting on Wednesday (see link for calendar). ... Exclusive disjunction (usual symbol xor) is a logical operator that results in true if one of the operands (not both) is true. ... This article is about the unit of information. ... The Baudot code, named after its inventor Émile Baudot, is a character set predating EBCDIC and ASCII and used originally and primarily on teleprinters. ... A teleprinter (teletypewriter, teletype or TTY) is a now largely obsolete electro-mechanical typewriter which can be used to communicate typed messages from point to point through a simple electrical communications channel, often just a pair of wires. ... Automotive style miniature relay A relay is an electrical switch that opens and closes under control of another electrical circuit. ... The plain text term has a different meaning. ... NSA can stand for: National Security Agency of the USA The British Librarys National Sound Archive This page concerning a three-letter acronym or abbreviation is a disambiguation page — a navigational aid which lists other pages that might otherwise share the same title. ...

One-time pad

Shortly thereafter, Joseph Mauborgne, at that time a captain in the US Army Signal Corps, proposed, in addition, that the paper tape key contain random information. The two ideas, when themselves combined, implement the one-time pad, though neither inventor used the name then. It was patented in the mid-1920s^{[citation needed]}. In the history of cryptography, Joseph Oswald Mauborgne (1881–1971) co-invented the one-time pad with Gilbert Vernam of Bell Labs. ... In ordinary language, the word random is used to express apparent lack of purpose or cause. ... Excerpt from a one-time pad. ... It has been suggested that this article or section be merged with Social issues of the 1920s. ...

Claude Shannon, also at Bell Labs, proved that the one-time pad is unbreakable (work done 1940-45; first published in Bell Labs Technical Journal 1948/49). It is the first and only encryption method for which there is such a proof. Claude Shannon Claude Elwood Shannon (April 30, 1916 – February 24, 2001), an American electrical engineer and mathematician, has been called the father of information theory, and was the founder of practical digital circuit design theory. ...

The Vernam cipher

In modern terminology, a Vernam cipher is a stream cipher in which the plaintext is XORed with a random or pseudorandom stream of data the same length to generate the ciphertext. If the stream of data is truly random and used only once, this is the one-time pad. Substituting pseudorandom data generated by a cryptographically secure pseudo-random number generator is a common and effective construction for a stream cipher. RC4 is an example of a Vernam cipher that is widely used on the Internet. The operation of A5/1, a LFSR-based stream cipher used to encrypt mobile phone conversations. ... A pseudo-random number is a number belonging to a sequence which appears to be random, but can in fact be generated by a finite computation. ... Excerpt from a one-time pad. ... A cryptographically secure pseudo-random number generator (CSPRNG) is a pseudo-random number generator (PRNG) with properties that make it suitable for use in cryptography. ... In cryptography, RC4 (or ARCFOUR) is the most widely-used software stream cipher and is used in popular protocols such as Secure Sockets Layer (SSL) (to protect Internet traffic) and WEP (to secure wireless networks). ...

Other patents

Other cryptographic patents filed by Vernam include:

• U.S. Patent 1,416,765
• U.S. Patent 1,584,749
• U.S. Patent 1,613,686

References

• Gilbert S. Vernam, "Cipher Printing Telegraph Systems For Secret Wire and Radio Telegraphic Communications", Journal of the IEEE, Vol 55, pp109-115 (1926).