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A key concept in epistemic logic, this problem highlights the importance of common knowledge. Some authors also refer to this as the Two Generals' Paradox, the Two Armies Problem, or the Coordinated Attack Problem. [1] [2] The Two Generals' Problem was the first computer communication problem to be proven to be unsolvable. [3]
In cryptography, a Caesar cipher, also known as Caesar's cipher, the shift cipher, Caesar's code, or Caesar shift, is one of the simplest and most widely known encryption techniques. It is a type of substitution cipher in which each letter in the plaintext is replaced by a letter some fixed number of positions down the alphabet .
[2] HackerRank categorizes most of their programming challenges into a number of core computer science domains, [3] including database management, mathematics, and artificial intelligence. When a programmer submits a solution to a programming challenge, their submission is scored on the accuracy of their output.
The following attack on the Caesar cipher allows full recovery of the secret key: Suppose the adversary sends the message: Attack at dawn, and the oracle returns Nggnpx ng qnja. The adversary can then work through to recover the key in the same way as a Caesar cipher. The adversary could deduce the substitutions A → N, T → G and so on. This ...
In a Caesar cipher, each letter of the alphabet is shifted along some number of places. For example, in a Caesar cipher of shift 3, a would become D, b would become E, y would become B and so on. The Vigenère cipher has several Caesar ciphers in sequence with different shift values.
Kasiski actually used "superimposition" to solve the Vigenère cipher. He started by finding the key length, as above. Then he took multiple copies of the message and laid them one-above-another, each one shifted left by the length of the key.
The Chaocipher [1] is a cipher method invented by John Francis Byrne in 1918 and described in his 1953 autobiographical Silent Years. [2] He believed Chaocipher was simple, yet unbreakable. Byrne stated that the machine he used to encipher his messages could be fitted into a cigar box .
He arrived with a small army and was released but died mysteriously in a rumoured suicide. The Helvetians went on with their plans for migration but were defeated in 58 BC and returned by Julius Caesar. The incident was the beginning of the Gallic War in which Caesar subjugated Gaul. [3]