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Introduced xoring of String and a sequence of Bytes #1814

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merged 3 commits into from
Nov 6, 2015
Merged

Introduced xoring of String and a sequence of Bytes #1814

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fe4b2e0
Introduced xoring of String and a sequence of Bytes
ppepos Nov 5, 2015
af6e899
Moved crypto services from String to Text
ppepos Nov 5, 2015
3575dd3
Optimized SequenceRead instantiation with fixed length in Text.xor
ppepos Nov 5, 2015
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39 changes: 33 additions & 6 deletions lib/crypto.nit
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Original file line number Diff line number Diff line change
Expand Up @@ -42,7 +42,7 @@ redef class Char
end
end

redef class String
redef class Text
# Performs a Rotation of `x` on each letter of self
#
# Works by replacing every character in `self` by its
Expand All @@ -65,7 +65,7 @@ redef class String
#
# NOTE : Works on letters only
# NOTE : This cipher is symmetrically decrypted with an `x` of 26-`x`
fun rot(x: Int): String do
fun rot(x: Int): Text do
var rot = x % 26
if rot < 0 then rot += 26
var d = new FlatBuffer.with_capacity(length)
Expand Down Expand Up @@ -93,7 +93,7 @@ redef class String
# Therefore, yielding the ciphertext : "fgounbmtcieehkh"
#
# assert "fuckingbehemoth".railfence(4) == "fgounbmtcieehkh"
fun railfence(depth: Int): String do
fun railfence(depth: Int): Text do
var lines = new Array[FlatBuffer].with_capacity(depth)
var up = false
for i in [0..depth[ do
Expand Down Expand Up @@ -127,10 +127,10 @@ redef class String
return r.to_s
end

# Transforms a rail-fence-encrypted String to its original
# Transforms a rail-fence-encrypted Text to its original
#
# assert "fgounbmtcieehkh".unrail(4) == "fuckingbehemoth"
fun unrail(depth: Int): String do
fun unrail(depth: Int): Text do
var dots = "." * length
var arr = new FlatBuffer.from(dots)
var start = 0
Expand All @@ -154,6 +154,33 @@ redef class String
end
return arr.to_s
end

# Returns `self` xored with `key`
#
# The shortest of the two is cycled through until the longest has been
# completely xored.
#
# assert "goodmorning".xor(" ".to_bytes) == "GOODMORNING"
fun xor(key: SequenceRead[Byte]): Text do
var xored = new Bytes.with_capacity(bytelen.max(key.length))

var shortest: SequenceRead[Byte]
var longest: SequenceRead[Byte]

if key.length > self.length then
shortest = self.to_bytes
longest = key
else
shortest = key
longest = self.to_bytes
end

for i in longest.length.times do
xored.add(longest[i] ^ shortest[i % shortest.length])
end

return xored.to_s
end
end

redef class Int
Expand Down Expand Up @@ -188,7 +215,7 @@ redef class Int
#
# In the end, our string is read using the generated array
#
# SEE: `String::unrail` for how the array is used
# SEE: `Text::unrail` for how the array is used
private fun unrail_paces: Array[Couple[Int, Int]] do
var ret = new Array[Couple[Int,Int]].with_capacity(self)
var extremes = new Couple[Int, Int]((self - 1) * 2, (self - 1) * 2)
Expand Down