ARC4 and ciphersaber crypting script

RC4 crypting method is a symmetric type of encryption, the ARC4 is the open source version of it. Ciphersaber, version 1 and version 2 are the improvements of that type of encryption. The following script permit to use ARC$ encryption and decrypt Ciphersaber V1 and V2 this way (use always binary data):


>> arcfour "w" to-binary "Hello world"
== #{52AD1ABFEC760C8B51875B}

>> to-string (arcfour "w" #{52AD1ABFEC760C8B51875B})
== "Hello world"


You can see that is a symmetric function and "w" is the key. Yo can manipulate any type of data, and reconvert it to the original.

Here another example with Ciphersaber v1 and v2:


>> to-string ciphersaber "asdfg" #{6F6D0BABF3AA6719031530EDB677CA74E0089DD0e7b8854356bb1448e37cdbefe7f3a84f4f5fb3fd}
== "This is a test of CipherSaber."

>> to-string ciphersaber/v2 "asdfg" #{ba9ab4cffb7700e618e382e8fcc5ab9813b1abc436ba7d5cdea1a31fb72fb5763c44cfc2ac77afee19ad} 10
== "This is a test of CipherSaber-2."


Here the source:

REBOL [
Title: "ARCFOUR and CipherSaber"
Date: 17-Jan-2004
File: %arcfour.r
Author: "Cal Dixon"
Purpose: {Provides encryption and decryption using the ARCFOUR algorithm}
Note: {this implementation can decrypt data at about 40KB/s on my 1Ghz AMD Duron system with Rebol/View 1.2.10.3.1}
Library: [
level: 'advanced
platform: 'all
type: [function module protocol]
domain: [encryption scheme]
tested-under: [view 1.2.10.3.1 on [W2K] by "Cal"]
license: 'PD
support: none
]
]

;ARCFOUR specification: http://www.mozilla.org/projects/security/pki/nss/draft-kaukonen-cipher-arcfour-03.txt
;CipherSabre specification: http://ciphersaber.gurus.com/faq.html#getrc4

arcfour-short: func [key [string! binary!] stream [binary! string!] /mix n /local state i j output swap addmod sz][
swap: func [a b s /local][ local: sz s a poke s a + 1 to-char sz s b poke s b + 1 to-char local ]
addmod: func [ a b ][ a + b // 256 ]
sz: func [ s a ][ pick s a + 1 ]
state: make binary! 256 repeat var 256 [ insert tail state to-char var - 1 ]
j: 0 loop any [ n 1 ] [ i: 0 loop 256 [ swap i j: addmod j add sz state i sz key i // length? key state i: i + 1] ]
i: j: 0 output: make binary! length? stream
repeat byte stream [
swap i: addmod i 1 j: addmod j sz state i state
insert tail output to-char xor~ byte to-char sz state addmod (sz state i) (sz state j)
]
clear state
return output
]

make root-protocol [
addmod: addmod: func [ a b ][ a + b // 256 ]
sz: func [ s a ][ pick s a + 1 ]
swap: func [a b s /local][ local: sz s a poke s a + 1 to-char sz s b poke s b + 1 to-char local ]
ins: get in system/words 'insert
i: 0 j: 0
open: func [port][
port/state/tail: 2000
port/state/index: 0
port/state/flags: port/state/flags or port-flags
port/locals: context [ inbuffer: make binary! 40000 state: make binary! 256]
use [key n i j] [
key: port/key
n: port/strength
repeat var 256 [ ins tail port/locals/state to-char var - 1 ]
j: 0 loop any [ n 1 ] [
i: 0 loop 256 [
swap i j: addmod j add sz port/locals/state i sz key i // length? key port/locals/state i: i + 1
]
]
]
i: j: 0
]
insert: func [port data][
system/words/insert tail port/locals/inbuffer data do []
]
copy: func [port /local output][
output: make binary! local: length? port/locals/inbuffer
loop local [
swap i: addmod i 1 j: addmod j sz port/locals/state i port/locals/state
ins tail output to-char sz port/locals/state addmod (sz port/locals/state i) (sz port/locals/state j)
]
local: xor~ output port/locals/inbuffer
clear port/locals/inbuffer
local
]
close: func [port][ clear port/locals/inbuffer clear port/locals/state clear port/url clear port/key]
port-flags: system/standard/port-flags/pass-thru
net-utils/net-install arcfour self 0
]

arcfour: func [key stream /mix n /local port][
port: open compose [scheme: 'arcfour key: (key) strength: (n)]
insert port stream
local: copy port
close port
return local
]

; CipherSaber is an ARCFOUR stream prepended with 10 bytes of random key data
ciphersaber: func [ key stream /v2 n ][
arcfour/mix join key copy/part stream 10 skip stream 10 either v2 [ any [ n 42 ] ][ 1 ]
]