Ruby on Rails Decryption

Question

The following function works perfect in PHP. How can it be translated in Ruby on Rails.

Please note that both privateKey and iv are 32 characters long.

mcrypt_decrypt(MCRYPT_RIJNDAEL_256, $privateKey, base64_decode($enc), MCRYPT_MODE_CBC, $iv)

I tried to use the following in Ruby but got a bad decrypt error.

cipher = OpenSSL::Cipher.new('aes-256-cbc')

cipher.decrypt
cipher.key = privateKey
cipher.iv = iv

decrypted = '' << cipher.update(encrypted) << cipher.final

You're not using this for a password, right?

Andrew Marshall
– Andrew Marshall

2012-04-11 14:10:22 +00:00
Commented Apr 11, 2012 at 14:10 — Andrew Marshall
– Andrew Marshall, Commented Apr 11, 2012 at 14:10

CupraR_On_Rails · Accepted Answer · 2012-04-11 12:31:47Z

1

Here some code which works for me :


def decrypt_data(data, pwd, iv)
    encrypted_data = Base64.decode64(data)
    aes = OpenSSL::Cipher::Cipher.new("AES-256-CBC")
    aes.decrypt
    aes.key = Digest::MD5.hexdigest(pwd)
    aes.iv = iv
    result = aes.update(encrypted_data) + aes.final 
end

In my example the password is encrypted with MD5.

I hope this help

answered Apr 11, 2012 at 12:31

CupraR_On_Rails

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9 Comments

user812120 Over a year ago

Many thanks for your quick response. However, this does not seem to work for me. I am new to Ruby on Rails. I will be very grateful if you could please tell me how to get the same results in Ruby on Rails as the following php code produces in php

user812120 Over a year ago

If I remove + aes.final from the above ruby code, I get a string but it is not readable. I I do not remove + aes.final, I get "bad decrypt" error

CupraR_On_Rails Over a year ago

I found this in php doc php.net/manual/fr/function.mcrypt-decrypt.php As you can see, the first comment sais "MCRYPT_RIJNDAEL_256 is not equivalent to AES_256". This is probably a way...

Andrew Marshall Over a year ago

MD5 does not encrypt, it hashes.

user812120 Over a year ago

I am still not getting the result the php code produces in php :( I am really stuck with this

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Sionide21 · Accepted Answer · 2012-04-11 11:35:41Z

0

You are base64 decoding it in the php example. Are you doing that in the ruby one as well?

require "base64"
Base64.decode64(encrypted)

Other than that, the code looks right to me.

answered Apr 11, 2012 at 11:35

Sionide21

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2 Comments

user812120 Over a year ago

Many thanks for your quick response Here is the complete PHP code $iv = base64_decode($_REQUEST["bpi"]); $enc = $_REQUEST["bpe"]; $sig = $_REQUEST["bps"]; $sig2 = hash_hmac("sha256", utf8_encode($iv . '.' . $enc), utf8_encode($privateKey)); echo(mcrypt_decrypt(MCRYPT_RIJNDAEL_256, $privateKey, base64_decode($enc), MCRYPT_MODE_CBC, $iv)); It works fine in PHP But the above Ruby code gives me a bad decrypt error. I am base64 decoding in ruby as well

user812120 Over a year ago

Is there a Ruby equivalent of MCRYPT_RIJNDAEL_256? If I use MCRYPT_RIJNDAEL_256 in PHP and AES-256-CBC in Ruby to encrypt the same data using the same key (32 characters) and iv (32 characters) and then base64 encode the encrypted data, I always get different results. However, if I use MCRYPT_RIJNDAEL_128 in php and AES-256-CBC in Ruby using a key (32 characters) and iv (16 characters) and then base64 encode the encrypted data, I get the same results.

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