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class RC4
def initialize(str)
begin
raise SyntaxError, "RC4: Key supplied is blank" if str.eql?('')
@q1, @q2 = 0, 0
@key = []
str.each_byte {|elem| @key << elem} while @key.size < 256
@key.slice!(256..@key.size-1) if @key.size >= 256
@s = (0..255).to_a
j = 0
0.upto(255) do |i|
j = (j + @s[i] + @key[i] )%256
@s[i], @s[j] = @s[j], @s[i]
end
end
end
def encrypt!(text)
process text
end
def encrypt(text)
process text.dup
end
alias_method :decrypt, :encrypt
private
def process(text)
text.unpack("C*").map { |c| c ^ round }.pack("C*")
end
def round
@q1 = (@q1 + 1)%256
@q2 = (@q2 + @s[@q1])%256
@s[@q1], @s[@q2] = @s[@q2], @s[@q1]
@s[(@s[@q1]+@s[@q2])%256]
end
end
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