Addons/convert/misc/vig
Vigenère Cipher
As an addon, load with
load'convert/misc/vig'
The Vigenère cipher is a method of encryption that uses a series of different Caesar ciphers based on the letters of a keyword. [{{#file: "vig.ijs"}} Download script: vig.ijs ]
NB.*vig c Vigenère cipher NB. cipher=. key 0 vig charset plain NB. plain=. key 1 vig charset cipher vig=: 2 : 0 : r=. (#y) $ n i.x n {~ (#n) | (r*_1^m) + n i.y ) «charsets» «encoded» Note 'Examples' «basic examples» «symmetry examples» «encoded examples» )
Different character sets can be used for different types of text. [{{#file: "charsets"}} Download script: charsets ]
NB. printable ASCII vigprn=: vig (TAB,CRLF,(32,:95) ];.0 a.) NB. alphabetic vigalpha=: vig ( (97,:26) ];.0 a. ) NB. acsii vigascii=: vig a.
Compare with the Wikipedia example. [{{#file: "basic examples"}} Download script: basic examples ]
(97,:26) ];.0 a. NB. alpha abcdefghijklmnopqrstuvwxyz 'lemon' 0 vigalpha 'attackatdawn' lxfopvefrnhr 'lemon' 1 vigalpha 'lemon' 0 vigalpha 'attackatdawn' attackatdawn
Symmetry
Vigenère cipher is a symmetric-key algorithm using the same key to encode and decode.
In addition, the encoding and decoding are interchangeable. [{{#file: "symmetry examples"}} Download script: symmetry examples ]
'lemon' 1 vigalpha 'attackatdawn' pphmpzwhpnlj 'lemon' 0 vigalpha 'lemon' 1 vigalpha 'attackatdawn' attackatdawn
Encodings
To work with the full range of 256 ascii symbols, it is convenient to represent the result of cypher in one of printable encodings. The encoded result is wrapped into several lines. [{{#file: "encoded"}} Download script: encoded ]
NB. base64 encoded vig64=: 1 : 0 : require 'convert/misc/base64' mv=. m vigascii x (_64 ]\ tobase64@mv)`(mv frombase64@(, -. CRLF,' '"_))@.m y ) NB. ascii85 encoded vig85=: 1 : 0 : require 'convert/misc/ascii85' mv=. m vigascii x (toascii85@mv)`(mv fromascii85)@.m y )
For example, [{{#file: "encoded examples"}} Download script: encoded examples ]
'lemon' 0 vig85 a. Ch@U+EcGl:GB\4... a. -: 'lemon' 1 vig85 'lemon' 0 vig85 a. 1 'lemon' 0 vig64 a. bGZvcnJxa3R3d3... a. -: 'lemon' 1 vig64 'lemon' 0 vig64 a. 1
See Also
- Vigenère cipher at Wikipedia
- ArcFour
- Essays/Under for Caesar cipher