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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.
Investigations. The following investigations are used in clearance determinations: [12] ANACI (Access National Agency Check with Inquiries) – Initial Confidential, Secret, L, LX; only used for civilian employees. NACLC (National Agency Check with Law and Credit) – Initial Confidential, Secret, L, LX; reinvestigations.
Four-square cipher. The four-square cipher is a manual symmetric encryption technique. [1] It was invented by the French cryptographer Felix Delastelle . The technique encrypts pairs of letters ( digraphs ), and thus falls into a category of ciphers known as polygraphic substitution ciphers. This adds significant strength to the encryption when ...
Caesar cipher. The action of a Caesar cipher is to replace each plaintext letter with a different one a fixed number of places down the alphabet. The cipher illustrated here uses a left shift of 3, so that (for example) each occurrence of E in the plaintext becomes B in the ciphertext. In cryptography, a Caesar cipher, also known as Caesar's ...
Book cipher. The King James Bible, a highly available publication suitable for the book cipher. A book cipher is a cipher in which each word or letter in the plaintext of a message is replaced by some code that locates it in another text, the key . A simple version of such a cipher would use a specific book as the key, and would replace each ...
1990. Dimensions. 11–12 feet × 20 feet. Location. George Bush Center for Intelligence, Langley, Virginia. Coordinates. 38°57′08″N 77°08′45″W. / 38.95227°N 77.14573°W / 38.95227; -77.14573. Kryptos is a distributed sculpture by the American artist Jim Sanborn located on the grounds of the Central Intelligence Agency (CIA ...
However, in cryptography, code has a more specific meaning: the replacement of a unit of plaintext (i.e., a meaningful word or phrase) with a code word (for example, "wallaby" replaces "attack at dawn"). A cypher, in contrast, is a scheme for changing or substituting an element below such a level (a letter, a syllable, or a pair of letters, etc ...
Top Secret is the highest level of classified information. Information is further compartmented so that specific access using a code word after top secret is a legal way to hide collective and important information. Such material would cause "exceptionally grave damage" to national security if made publicly available.