RSA暗号方式の復号@某ES-2

hakuhoudou2.rb

require 'uri'
require 'prime'

# RSA暗号
# 公開鍵(E, N)
E = 47 #適当な正整数
N = 323 #素数p * 素数q
D_RANGE = 1000 #秘密鍵の推定最大値(一応ループ回避)

def decryption(x, d)
	return ((x.to_i ** d) % N).to_s(16)
end

p, q = -1, -1
Prime.each((N/2) - 1) do |prime|
	if N % prime == 0
		p = prime
		q = N / prime
	end
end

puts "p = #{p}, q = #{q}"

raise("N is not valid status") if p == -1

lcm = (p-1).lcm(q-1) 
p "lcm = #{lcm}"
for d in (0..D_RANGE+1) # d: 秘密鍵 
	tmp = E * d
	break if tmp % lcm == 1
end

raise("Not found Secret key under #{D_RANGE}") if d == D_RANGE + 1
puts "d = #{d}"

buf = ""
isTailPercent = true
File::open(ARGV[0]) {|file| 
	file.each {|line|
		line = buf + line.strip
		isTailPercent = (line[line.length-1] == '%') 
		line = line.split('%')
		line = line[1..line.length-1] #1要素目は空になるため 
		i = -1
		loop do
			i += 1
			break if i == line.length-1
			if (i + 1) % 3 == 0
				line[(i - 2)..i] = decryption(line[i-2], d), decryption(line[i-1], d), decryption(line[i], d)
				print URI.decode('%' + line[(i - 2)..i].join("%"))
				line = line[i+1..line.length-1]
				i -= 3
			end
		end
		buf = (line.length >= 1 ? '%' : '') + line.join('%') +  (isTailPercent ? '%' : '')
	}
}