Diplomats had long used codes and ciphers for confidentiality and to minimize telegraph costs. The next development was the paper pad system. Together they invented the first one-time tape system. Army and later chief of the Signal Corps) recognized that the character sequence on the key tape could be completely random and that, if so, cryptanalysis would be more difficult. Joseph Mauborgne (then a captain in the U.S. Each character in a message was electrically combined with a character on a punched paper tape key. Patent 1,310,719) a cipher based on teleprinter technology. In 1917, Gilbert Vernam (of AT&T Corporation) invented and later patented in 1919 ( U.S. The next one-time pad system was electrical. 5.2 Quantum and post-quantum cryptographyįrank Miller in 1882 was the first to describe the one-time pad system for securing telegraphy.
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There is some ambiguity to the term "Vernam cipher" because some sources use "Vernam cipher" and "one-time pad" synonymously, while others refer to any additive stream cipher as a "Vernam cipher", including those based on a cryptographically secure pseudorandom number generator (CSPRNG). To increase security, one-time pads were sometimes printed onto sheets of highly flammable nitrocellulose, so that they could easily be burned after use. The KGB used pads of such size that they could fit in the palm of a hand, or in a walnut shell.
For concealment the pad was sometimes so small that a powerful magnifying glass was required to use it. The "pad" part of the name comes from early implementations where the key material was distributed as a pad of paper, allowing the current top sheet to be torn off and destroyed after use. One-time use came later, when Joseph Mauborgne recognized that if the key tape were totally random, then cryptanalysis would be impossible.
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In its original form, Vernam's system was vulnerable because the key tape was a loop, which was reused whenever the loop made a full cycle. Derived from his Vernam cipher, the system was a cipher that combined a message with a key read from a punched tape. Patent 1,310,719 was issued to Gilbert Vernam for the XOR operation used for the encryption of a one-time pad.
Digital versions of one-time pad ciphers have been used by nations for critical diplomatic and military communication, but the problems of secure key distribution make them impractical for most applications.įirst described by Frank Miller in 1882, the one-time pad was re-invented in 1917. It has also been mathematically proven that any cipher with the property of perfect secrecy must use keys with effectively the same requirements as OTP keys.
It is not sufficient for OTP keys to pass statistical randomness tests as such tests cannot measure entropy, and the number of bits of entropy must be at least equal to the number of bits in the plaintext. The key must be random ( uniformly distributed in the set of all possible keys and independent of the plaintext), entirely sampled from a non-algorithmic, chaotic source such as a hardware random number generator.The key must be at least as long as the plaintext.The resulting ciphertext will be impossible to decrypt or break if the following four conditions are met: Then, each bit or character of the plaintext is encrypted by combining it with the corresponding bit or character from the pad using modular addition. In this technique, a plaintext is paired with a random secret key (also referred to as a one-time pad). In cryptography, the one-time pad ( OTP) is an encryption technique that cannot be cracked, but requires the use of a single-use pre-shared key that is not smaller than the message being sent.
The table on the right is an aid for converting between plaintext and ciphertext using the characters at left as the key.
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National Security Agency, code named DIANA. A format of one-time pad used by the U.S.
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