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rc4.r

REBOL [ Title: "Basic RC4 algorithm" Date: 29-Apr-2004 File: %rc4.r Author: "Arthur Beltrao (Brasil)" Email: "%arthurbeltrao--yahoo--com--br" Purpose: {Provides encryption and decryption using the basic RC4 algorithm} Note: {You can evaluate the En/Decrypt performance using the elapsed function} Library: [ level: 'advanced platform: 'all type: [function module] domain: [encryption] tested-under: [view 1.2.10.3.1 on [W2K] by "Arthur Beltrao"] license: 'PD support: none ] ] rc4_state: make object! [ x: 0 y: 0 m: [] ] rc4_setup: func [ {Initializes the rc4_state object used in En/Decrypt function.} key [binary! string!] "Crypt key" /local i j k a ][ rc4_state/x: 0 rc4_state/y: 0 rc4_state/m: copy [] for i 0 255 1 [ append rc4_state/m i ] j: 0 k: 0 for i 0 255 1 [ a: pick rc4_state/m i + 1 j: (j + a + pick key (k + 1)) and 255 poke rc4_state/m (i + 1) pick rc4_state/m (j + 1) poke rc4_state/m (j + 1) a k: k + 1 if k >= length? key [ k: 0 ] ] ] rc4_crypt: func [ {En/Decrypts the data, using the pre-initialized rc4_state object.^/^- The rc4_state must be initialized first by the rc4_setup function.} data [binary! string!] "Data to En/Decrypt" /local i x y a b new_data ][ x: rc4_state/x y: rc4_state/y new_data: copy #{} i: 0 while [ i < length? data ] [ x: x + 1 and 255 a: pick rc4_state/m x + 1 y: y + a and 255 b: pick rc4_state/m y + 1 poke rc4_state/m x + 1 b poke rc4_state/m y + 1 a append new_data to-char (pick data i + 1) xor (pick rc4_state/m a + b and 255 + 1) i: i + 1 ] rc4_state/x: x rc4_state/y: y return new_data ] rc4: func [ {Provides encryption and decryption using the basic RC4 algorithm.} key [binary! string!] "En/Decrypt key" data [binary! string!] "Data to En/Decrypt" ][ rc4_setup key return rc4_crypt data ] elapsed: func [ {Returns the elapsed time since the begining of an operation. Ex: elapsed [ rc4 read %rc4.r "testing" ]} body [block!] "Operation to calculate the elapsed time" /local stime ][ stime: now/precise do body return difference now/precise stime ]
halt ;; to terminate script if DO'ne from webpage
Notes
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  • (arthurbeltrao:yahoo:com:br)