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Merge pull request #78 from Doppon/fix-ciphers-example

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Ciphers MerkleHellman: Unify indentation for 2 spaces
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Doppo 2021-01-14 07:31:29 +09:00 committed by GitHub
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1 changed files with 54 additions and 55 deletions
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109
ciphers/merkle_hellman_cryptosystem.rb
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@ -1,61 +1,60 @@
require'openssl';
class MerkleHellman
SMALLEST_KNAPSACK_ITEM = 2**32
STEP = 2**32
def initialize size
@size = size;
sum = SMALLEST_KNAPSACK_ITEM;
@easy_knapsack = size.times.map do|k|
x = sum + rand(STEP);
sum += x;
x;
end
@n = sum + rand(STEP);
loop do
@a = rand(0..@n);
break if @a.gcd(@n) == 1;
end
@hard_knapsack = @easy_knapsack.map do|x|
(@a * x) % @n;
end
end
def encrypt msg
raise ArgumentError, "max length is #{@size/8} characters" if msg.length * 8 > @size;
c = 0;
msg.each_codepoint.reverse_each.with_index do|ch,i|
7.downto(0) do|j|
wj = ch.>>(j).& 1;
c += wj * @hard_knapsack[i*8+7-j]
end
end
c;
end
def decrypt c
p = @a.to_bn.mod_inverse(@n).mod_mul(c,@n).to_i;
byte = 0;
msg = [ ];
@easy_knapsack.reverse_each.with_index do|x,i|
bit = 0;
if p >= x
p -= x;
bit = 1;
end
byte |= (bit << (i%8));
if i % 8 == 7
msg << byte.chr;
byte = 0;
end
end
msg.join;
end
attr_accessor :hard_knapsack;
SMALLEST_KNAPSACK_ITEM = 2**32
STEP = 2**32
def initialize size
@size = size;
sum = SMALLEST_KNAPSACK_ITEM;
@easy_knapsack = size.times.map do |k|
x = sum + rand(STEP);
sum += x;
x;
end
@n = sum + rand(STEP);
loop do
@a = rand(0..@n);
break if @a.gcd(@n) == 1;
end
@hard_knapsack = @easy_knapsack.map do |x|
(@a * x) % @n;
end
end
def encrypt msg
raise ArgumentError, "max length is #{@size/8} characters" if msg.length * 8 > @size;
c = 0;
msg.each_codepoint.reverse_each.with_index do |ch,i|
7.downto(0) do|j|
wj = ch.>>(j).& 1;
c += wj * @hard_knapsack[i*8+7-j]
end
end
c;
end
def decrypt c
p = @a.to_bn.mod_inverse(@n).mod_mul(c,@n).to_i;
byte = 0;
msg = [ ];
@easy_knapsack.reverse_each.with_index do |x,i|
bit = 0;
if p >= x
p -= x;
bit = 1;
end
byte |= (bit << (i%8));
if i % 8 == 7
msg << byte.chr;
byte = 0;
end
end
msg.join;
end
attr_accessor :hard_knapsack;
end
str = "Hello there, this is my plaintext";