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T3 or T3R - Tier 3 or Tier 3 Reinvestigation, now replace all NACLC. T5 and T5R - Tier 5 or Tier 5 Reinvestigation, now replace SSBI and SBPR respectively. Yankee White – An investigation required for personnel working with the President and Vice President of the United States. Obtaining such clearance requires, in part, an SSBI.
An example of a U.S. classified document; page 13 of a United States National Security Agency report [31] on the USS Liberty incident, partially declassified and released to the public in July 2003. The original overall classification of the page, "Top Secret" code word UMBRA, is shown at top and bottom. The classification of individual ...
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 ...
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. [4] 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. [5] Such material would cause "exceptionally grave damage" to national security if made publicly available. [6]
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.
Cryptography, the use of codes and ciphers to protect secrets, began thousands of years ago. [ 1] Until recent decades, it has been the story of what might be called classical cryptography — that is, of methods of encryption that use pen and paper, or perhaps simple mechanical aids. In the early 20th century, the invention of complex ...
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 ...