# Ezcrypto

**URL:** <https://www.ruby-forum.com/t/ezcrypto/106848>\
**Category:** Ruby\
**Created:** [June 14, 2007, 5:05pm UTC](https://www.ruby-forum.com/t/ezcrypto/106848 "2007-06-14T17:05:17Z")\
**Posts on this page:** 9\
**Page:** 1

<div class="post-metadata">

**Author:** ![bob](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/ea666f/32.png) [@bob](https://www.ruby-forum.com/u/bob)\
**Post date:** [June 14, 2007, 5:05pm UTC](https://www.ruby-forum.com/t/ezcrypto/106848/1 "2007-06-14T17:05:17Z")

</div>

require ‘ezcrypto’

key = EzCrypto::Key.new “1234567812345678”, :algorithm=\>“blowfish”  
key.encrypt\_file “en.dll”, “crypt.dll”  
key.decrypt\_file “crypt.dll”,“en.dll”

encrypts the 4,382,208 bytes file into a 29,003 bytes file decrypting  
this then obviously fails. This code works ok with small text files ok.

Oh please don’t RTFM me cos the documentation is up to the usual Ruby  
standard 😉  
Ruby, so much power so little documentation.

Thanks for any help,  
Bob

---

<div class="post-metadata">

**Author:** ![bob](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/ea666f/32.png) [@bob](https://www.ruby-forum.com/u/bob)\
**Post date:** [June 14, 2007, 5:43pm UTC](https://www.ruby-forum.com/t/ezcrypto/106848/2 "2007-06-14T17:43:05Z")

</div>

And you are posting this to Ruby-lang why? Sounds like you didn’t even  
try  
to contact the author of EzCrypto.

[http://ezcrypto.rubyforge.org/](http://ezcrypto.rubyforge.org/)

And too bad, I’m going to tell you to RTFM. I checked it out (I have no  
prior knowledge of this library) and I think I already know what’s wrong  
with your code:

Key#new:  
“Initialize the key with raw unencoded binary key data. This needs to be  
at  
least 16 bytes long for the default aes-128 algorithm.”

It wants “raw binary key data”. A Ruby string is not “raw binary key  
data”.

Otherwise, I was unable to get it working with blowfish or aes-128-cbc,  
so  
either go get a hold of the author and ask, try to fix the problem  
yourself,  
or assume that the library is broken (it was released in Sept 2006) and  
move  
on.

Jason

---

<div class="post-metadata">

**Author:** ![bob](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/ea666f/32.png) [@bob](https://www.ruby-forum.com/u/bob)\
**Post date:** [June 14, 2007, 6:04pm UTC](https://www.ruby-forum.com/t/ezcrypto/106848/3 "2007-06-14T18:04:22Z")

</div>

The manual actually sucks, but I would still recommend joining the  
ezcrypto  
mailing list. I think we are seeing the same reoccuring problem with  
crypo  
libraries on this mailing list and that is the fact that you MUST  
specify  
exactly which cipher mode to use. Most of the crypto libraries just  
wrap  
openssl and alot of the default cipher modes they use only operate on  
binary  
data in specific sized chunks.

[http://openssl.org/docs/crypto/blowfish.html#](http://openssl.org/docs/crypto/blowfish.html#)

- Nathan

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<div class="post-metadata">

**Author:** ![bob](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/ea666f/32.png) [@bob](https://www.ruby-forum.com/u/bob)\
**Post date:** [June 14, 2007, 10:34pm UTC](https://www.ruby-forum.com/t/ezcrypto/106848/4 "2007-06-14T22:34:55Z")

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Without seeing your code I can only speculate what the root problem is,  
but  
from the \> 256 byte error description it sounds like you are using a  
block  
cipher that expects you to hand it 256 byte max chunks of data at a  
time. I  
would look at trying to use a stream cipher that allows a variable  
amount of  
data to be passed to it. My knowledge of the openssl lib is not deep so  
I  
can’t really show this in code right now but I will try to put an  
example up  
later today. I can say however that using a crypto library is more  
complex  
than just creating an object and handing it a (key, plaintext, salt)  
type  
argument. You have to understand the default cipher that is being used  
by  
the method during creation or you will not pass the data in the expected  
format. There is more to the implementation than the crypto algorithm  
of  
choice. Blowfish is a block cipher algorithm, yet there are multiple  
“block  
modes” that it uses. I.E. ECB (_electronic codebook)_, CBC  
(_cipher-block  
chaining)_, OFB (_output feedback)_, CFB (_cipher feedback)_.  
Wikipedia.orghas a pretty good explanation of the modes.

> **[Block cipher mode of operation](https://en.wikipedia.org/wiki/Block_cipher_modes_of_operation)**
>
> In cryptography, a block cipher mode of operation is an algorithm that uses a block cipher to provide information security such as confidentiality or authenticity. A block cipher by itself is only suitable for the secure cryptographic transformation (encryption or decryption) of one fixed-length group of bits called a block. A mode of operation describes how to repeatedly apply a cipher's single-block operation to securely transform amounts of data larger than a block.
> Most modes require a uniqu...

You do not need to understand the mathematical formulas to implement,  
however you should have a basic understanding of each mode to choose the  
proper one for your implementation. From the few minutes I’ve looked at  
the  
openssl documentation it looks like you have to specify a mode and then  
depending on the mode chose you have a setup phase, encryption phase,  
and  
decryption phase. I also looked at a few lines of the ezcrypto binding  
and  
it looks like doesn’t do anything except wrap the C API for openssl so  
this  
link should give you a basic idea of what you’re looking for in  
implementation.

[http://www.openssl.org/docs/crypto/blowfish.html](http://www.openssl.org/docs/crypto/blowfish.html)

Unfortunately as you’ve previously stated the Ruby specific  
documentation is  
almost nil on this subject. I will try to put something small up  
tonight.

- Nathan

---

<div class="post-metadata">

**Author:** ![bob](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/ea666f/32.png) [@bob](https://www.ruby-forum.com/u/bob)\
**Post date:** [June 15, 2007, 11:09am UTC](https://www.ruby-forum.com/t/ezcrypto/106848/5 "2007-06-15T11:09:54Z")

</div>

here’s some basic code that will encrypt a file with blowfish and CBC,  
note it doesn’t do the last block of the file that is less than 8 bytes.

require ‘openssl’

key = “1234567812345678”  
alg = “BF-CBC”  
iv = “00000000”

bf = OpenSSL::Cipher::Cipher.new(alg)  
bf.encrypt  
bf.key = key  
bf.iv = iv

File.open(“openssl.dat”,‘wb’) do |enc|

File.open(“test.txt”,“rb”) do |f|  
size = File.size(“test.txt”)  
blocks = size / 8

```
for i in 1..blocks
  r = f.read(8)
  cipher = bf.update(r)
  enc << cipher
end

```

end

enc \<\< bf.final  
end

You can also speed it up by doing more efficient read from file, anyhoo  
Openssl file encryption with Blowfish seems ok, I can get back on with  
the work I’m meant to be doing now 🙂

Jim.

---

<div class="post-metadata">

**Author:** ![bob](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/ea666f/32.png) [@bob](https://www.ruby-forum.com/u/bob)\
**Post date:** [June 15, 2007, 11:12am UTC](https://www.ruby-forum.com/t/ezcrypto/106848/6 "2007-06-15T11:12:03Z")

</div>

Also note that it does not write the IV at the beginning of the file,  
would be something you need to add if you require that.

Oh and I was able to decrypt this using my C version of Blowfish not  
from Openssl.

Jim.

---

<div class="post-metadata">

**Author:** ![bob](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/ea666f/32.png) [@bob](https://www.ruby-forum.com/u/bob)\
**Post date:** [June 15, 2007, 5:52pm UTC](https://www.ruby-forum.com/t/ezcrypto/106848/7 "2007-06-15T17:52:25Z")

</div>

It seems like you would need to add padding to this method to encrypt  
the  
whole file, but then how would your decryption process know how to  
remove  
the padding unless it is implemented in the same program? Must be a  
better  
way to do this using openssl/ezcrypto. I have Applied Cryptography  
sitting  
on my desk right now which should provide a clue on how this is usually  
handled. Unfortunately I also have “required” work to do today. 😛  
Hope  
to keep this thread alive and work it to a resolution soon.

- Nathan

---

<div class="post-metadata">

**Author:** ![bob](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/ea666f/32.png) [@bob](https://www.ruby-forum.com/u/bob)\
**Post date:** [June 14, 2007, 10:06pm UTC](https://www.ruby-forum.com/t/ezcrypto/106848/8 "2007-06-14T22:06:06Z")

</div>

Hmmm I get the same problem, seems like it dies if the file is greater  
than 256 bytes, dunno if that means much.

I don’t think what Jason said is very relevant, and their does seem to  
be an issue. The documentation is typically bad and I personally do  
find that very annoying, people can find the time to write blogs and  
publish this stuff but can’t spend 10 minutes writing some simple sample  
code. I have posted on the relevant ruby forge forum but I would not  
expect to get a message anytime soon.

Fixing the bug might well be very time consuming as it is a wrapper  
around Openssl, and we don’t know if the issue is with that or ezcrypto.

Move on then I guess, but to what? The crypto gem works okay if you only  
need to crypt small files but is very slow on big files, not practical  
for our plans.

Look at OpenSSL gem directly I guess, but you will have a hard time  
finding useful documentation for that either me thinks.

Anyone know how to crypt files with Blowfish using Openssl, to late at  
night now for me to try that!

Jim.

---

<div class="post-metadata">

**Author:** ![bob](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/ea666f/32.png) [@bob](https://www.ruby-forum.com/u/bob)\
**Post date:** [June 18, 2007, 12:40pm UTC](https://www.ruby-forum.com/t/ezcrypto/106848/9 "2007-06-18T12:40:37Z")

</div>

File.open(“test.enc”,‘wb’) do |enc|

File.open(“test.txt”,“rb”) do |f|  
size = File.size(“test.txt”)  
blocks = size / 8

```
for i in 1..blocks
  r = f.read(8)
  cipher = bf.update(r)
  enc << cipher
end

if size%8 >0
  r = f.read((size%8))
  cipher = bf.update(r)
  enc << cipher
end

```

end

enc \<\< bf.final  
end

That does the trick, I think the bf.final should sort out the padding.  
In fact I wouldn’t be surprised if you didn’t have to feed update 8  
bytes at a time, but not tested…NOTE: this is just test code that  
works, and isn’t efficient.

Jim.