The DRYAD Numeral Cipher/Authentication System (KTC 1400 D) is a simple, paper cryptographic system currently in use by the United States military for authentication and for encryption of short, numerical messages. Every unit with a radio is given a set of DRYAD code sheets. A single sheet is valid for a limited time (e.g. 6 hours), called a ''cryptoperiod.'' A DRYAD code sheet contains 25 lines or rows indexed by the letters in a column on the left of the page. Each row contains a random permutation of the letters A thru Y. The letters in each row are grouped into 10 columns labeled 0 thru 9. The columns under 0, 1, 2 and 5 have more letters that the other digits, which have just two each. DRYAD is used in two modes, authentication and encryption. For authentication, a challenging station selects two letters from A thru Y at random. The challenged station uses the first letter to select a row in the currently active DRYAD page. The second letter is then located in the row and the letter ''below'' it is the response. (One obvious problem here is that an enemy trying to penetrate a network has one chance in 25 of guessing the right response. On the other hand, a two character response would reduce the useful life of a page.) The second mode is used to encrypt short numeric information, like map coordinates or a new radio frequency. The coder selects two letters at random. The first selects a row in the current active page. The second letter is used as in the authentication mode, except the letter to the right is selected and called the "SET LETTER." Numbers are enciphered one digit at a time. A ciphertext letter is chosen from the selected row in the column under the plain text digit. If the digit occurs more than once in the number, the coder is instructed to choose a different letter in the same column. All the digits in a single plaintext number are encoded from the same row. (There is also a provision for encoding letters associated with map grid coordinates.) While crude, this system has the advantage of being fast, relatively easy and not requiring even a pencil. The presence of more cipher-text columns under the digits 0, 1 and 5, is apparently intended to make ciphertext frequency analysis more difficult. But much of the security comes from keeping the cryptoperiod short. ==See also:== * M-94 tactical cipher used in WWII. * Dryad's original meaning in mythology. Classical ciphers Encryption devices
Dryads are Tree (mythology) spirits in Greek mythology. Technically speaking, dryads are the nymphs of oak trees, but the term has come to be used for all tree nymphs in general. ''Drys'' in Greek signifies 'oak,' from an Indo-European root ''*derew(o)-'' 'tree' or 'wood.' The nymphs of ash (tree) trees were called the Meliai. The ash-tree sisters tended the infant Zeus in Rhea (mythology)'s Cretan cave. Rhea gave birth to the Meliai after being made fertile by the cast-away genitals of Ouranos. Dryads, like all nymphs, were supernaturally long-lived and tied to their homes, but some were a step beyond most nymphs. These were the hamadryads who were said to form an integral part of their trees, such that if the tree died, the hamadryad associated with it died as well. For these reasons, dryads and the Greek gods punished any mortals who harmed trees without first propitiating the tree-nymphs. See also the myth of Daphne, who was pursued by Apollo and became a dryad associated with the laurel. ==External links== *[http://homepage.mac.com/cparada/GML/NYMPHS.html Greek Mythology Link: Nymphs.] Nymphs
I have editted this article twice to reflect the myths, in which ''hamadryads'' die if their trees are cut down and ''not'' ordinary dryads, and to agree with the hamadryad article. Please, do not change this again. For Future Reference: Dryad = Wood Elf (not supernaturally tied to the trees, but still acting as mythologic eco-defenders/terrorists) Hamadryad = Wood Elf that IS TIED TO A TREE SUPERNATURALLY ''(unsigned, but by 66.139.107.120)'' :For future reference, that sounds like something you got out of a game of Dungeons and Dragons. Hamadryads are just a specific kind of dryad. If you claim otherwise, provide an actual scholarly source to back up what you claim, please. User:DreamGuy 15:02, May 12, 2005 (UTC)
See other meanings of words starting from letter:
Words begining with Dryad:
DRYAD
Dryad
Dryad
Dryad's_Saddle
Dryades
Dryads
DRYAD_(Cryptography)
DRYAD
The DRYAD Numeral Cipher/Authentication System (KTC 1400 D) is a simple, paper cryptographic system currently in use by the United States military for authentication and for encryption of short, numerical messages. Every unit with a radio is given a set of DRYAD code sheets. A single sheet is valid for a limited time (e.g. 6 hours), called a ''cryptoperiod.'' A DRYAD code sheet contains 25 lines or rows indexed by the letters in a column on the left of the page. Each row contains a random permutation of the letters A thru Y. The letters in each row are grouped into 10 columns labeled 0 thru 9. The columns under 0, 1, 2 and 5 have more letters that the other digits, which have just two each. DRYAD is used in two modes, authentication and encryption. For authentication, a challenging station selects two letters from A thru Y at random. The challenged station uses the first letter to select a row in the currently active DRYAD page. The second letter is then located in the row and the letter ''below'' it is the response. (One obvious problem here is that an enemy trying to penetrate a network has one chance in 25 of guessing the right response. On the other hand, a two character response would reduce the useful life of a page.) The second mode is used to encrypt short numeric information, like map coordinates or a new radio frequency. The coder selects two letters at random. The first selects a row in the current active page. The second letter is used as in the authentication mode, except the letter to the right is selected and called the "SET LETTER." Numbers are enciphered one digit at a time. A ciphertext letter is chosen from the selected row in the column under the plain text digit. If the digit occurs more than once in the number, the coder is instructed to choose a different letter in the same column. All the digits in a single plaintext number are encoded from the same row. (There is also a provision for encoding letters associated with map grid coordinates.) While crude, this system has the advantage of being fast, relatively easy and not requiring even a pencil. The presence of more cipher-text columns under the digits 0, 1 and 5, is apparently intended to make ciphertext frequency analysis more difficult. But much of the security comes from keeping the cryptoperiod short. ==See also:== * M-94 tactical cipher used in WWII. * Dryad's original meaning in mythology. Classical ciphers Encryption devices
Dryad
Dryads are Tree (mythology) spirits in Greek mythology. Technically speaking, dryads are the nymphs of oak trees, but the term has come to be used for all tree nymphs in general. ''Drys'' in Greek signifies 'oak,' from an Indo-European root ''*derew(o)-'' 'tree' or 'wood.' The nymphs of ash (tree) trees were called the Meliai. The ash-tree sisters tended the infant Zeus in Rhea (mythology)'s Cretan cave. Rhea gave birth to the Meliai after being made fertile by the cast-away genitals of Ouranos. Dryads, like all nymphs, were supernaturally long-lived and tied to their homes, but some were a step beyond most nymphs. These were the hamadryads who were said to form an integral part of their trees, such that if the tree died, the hamadryad associated with it died as well. For these reasons, dryads and the Greek gods punished any mortals who harmed trees without first propitiating the tree-nymphs. See also the myth of Daphne, who was pursued by Apollo and became a dryad associated with the laurel. ==External links== *[http://homepage.mac.com/cparada/GML/NYMPHS.html Greek Mythology Link: Nymphs.] Nymphs
Dryad
I have editted this article twice to reflect the myths, in which ''hamadryads'' die if their trees are cut down and ''not'' ordinary dryads, and to agree with the hamadryad article. Please, do not change this again. For Future Reference: Dryad = Wood Elf (not supernaturally tied to the trees, but still acting as mythologic eco-defenders/terrorists) Hamadryad = Wood Elf that IS TIED TO A TREE SUPERNATURALLY ''(unsigned, but by 66.139.107.120)'' :For future reference, that sounds like something you got out of a game of Dungeons and Dragons. Hamadryads are just a specific kind of dryad. If you claim otherwise, provide an actual scholarly source to back up what you claim, please. User:DreamGuy 15:02, May 12, 2005 (UTC)
See other meanings of words starting from letter:
D
DA | DB | DC | DE | DF | DG | DH | DI | DJ | DK | DL | DM | DN | DO | DP | DR | DS | DT | DU | DW | DX | DY | DZ |Words begining with Dryad:
DRYAD
Dryad
Dryad
Dryad's_Saddle
Dryades
Dryads
DRYAD_(Cryptography)
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