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In cryptography, a substitution cipher is a method of encrypting in which units of plaintext are replaced with the ciphertext, in a defined manner, with the help of a key; the "units" may be single letters (the most common), pairs of letters, triplets of letters, mixtures of the above, and so forth. The receiver deciphers the text by performing ...
For the codes, words and phrases were converted to groups of numbers (typically 4 or 5 digits) using a dictionary-like codebook. For added security, secret numbers could be combined with (usually modular addition) each code group before transmission, with the secret numbers being changed periodically (this was called superencryption ).
The pigpen cipher (alternatively referred to as the masonic cipher, Freemason's cipher, Rosicrucian cipher, Napoleon cipher, and tic-tac-toe cipher) [2] [3] is a geometric simple substitution cipher, which exchanges letters for symbols which are fragments of a grid. The example key shows one way the letters can be assigned to the grid.
Two-factor authentication ( 2FA) is a method of adding additional security to your account. The first "factor" is your usual password that is standard for any account. The second "factor" is a verification code retrieved from an app on a mobile device or computer. 2FA is conceptually similar to a security token device that banks in some ...
This "code" is one of many innocuous sounding secret codes that stores use to alert employees to problems without distracting you from shopping. We tracked down some current and former retail ...
Casting out nines. Casting out nines is any of three arithmetical procedures: [1] Adding the decimal digits of a positive whole number, while optionally ignoring any 9s or digits which sum to 9 or a multiple of 9. The result of this procedure is a number which is smaller than the original whenever the original has more than one digit, leaves ...
A numbers station is a shortwave radio station characterized by broadcasts of formatted numbers, which are believed to be addressed to intelligence officers operating in foreign countries. [1] Most identified stations use speech synthesis to vocalize numbers, although digital modes such as phase-shift keying and frequency-shift keying, as well as Morse code transmissions, are not uncommon ...
Country calling codes, country dial-in codes, international subscriber dialing ( ISD) codes, or most commonly, telephone country codes are telephone number prefixes for reaching telephone subscribers in foreign countries or areas via international telecommunication networks.