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Fixed key generation length #21

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Fixed key generation length #21

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5 changes: 2 additions & 3 deletions lib/aes/aes.rb
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Original file line number Diff line number Diff line change
Expand Up @@ -84,7 +84,7 @@ def random_iv

# Generate a random key
def random_key(length=256)
_random_seed.unpack('H*')[0][0..((length/8)-1)]
_random_seed.unpack('H*')[0][0..((length/4)-1)]
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@jteich jteich Sep 22, 2022

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The key as generated by _random_seed is a hex string. In a hex string, each character encodes 4 bits.

end

private
Expand All @@ -94,8 +94,7 @@ def _random_seed(size=32)
if defined? OpenSSL::Random
return OpenSSL::Random.random_bytes(size)
else
chars = ("a".."z").to_a + ("A".."Z").to_a + ("0".."9").to_a
(1..size).collect{|a| chars[rand(chars.size)] }.join
(1..size).collect{ rand(256).chr }.join
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@jteich jteich Sep 22, 2022

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When using a modulo based upon a-z,A-Z,0-9 which comprises 62 characters, this effectively yields log2(62) (about 5.95) bits per character of randomness. rand(256) will yield a full 8 bits per character, inline with what OpenSSL::Random.random_bytes would return.

end
end

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4 changes: 2 additions & 2 deletions test/test_aes.rb
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Expand Up @@ -32,8 +32,8 @@ class TestAES < Test::Unit::TestCase
end

should "generate a new key when AES#key" do
assert_equal 32, AES.key.length
assert_equal 44, AES.key(256, :base_64).length
assert_equal 64, AES.key.length
assert_equal 89, AES.key(256, :base_64).length
end

end