[erlang-questions] blowfish cbc mode decrypt

Rad Gruchalski <>
Mon Nov 9 10:40:52 CET 2015


Bogdan,

I wonder if you can show us a minimum viable example.  
How do you encrypt, how do you decrypt. Can you present such code?










Kind regards,

Radek Gruchalski

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On Monday, 9 November 2015 at 10:38, Bogdan Andu wrote:

>  
> hi,
>  
> I really need some pointers about this issue
>  
> as i tried all kinds of combinations of IV and body
> to be decrypted.
>  
> Am i missing something or there is a bug in cipher
> blowfish_cbc ?
>  
>  
>  
> On Thu, Nov 5, 2015 at 3:51 PM, Bogdan Andu < (mailto:)> wrote:
> >  Data to be decrypted (arrived on socket, etc) is:
> > <<IvSpec:8/binary, IV:8/binary, Rest/binary>> = EncryptedData
> >  
> > IV is ectracted form the 8-byte prepanded value preceding  
> > IvSpec which has the value RandomIV.
> >  
> > decryption of Rest should be initialized with IV.
> >  
> >  
> > On Thu, Nov 5, 2015 at 3:38 PM, Radoslaw Gruchalski < (mailto:)> wrote:
> > > You say your data is:
> > >  
> > > <<IvSpec>> == <<RandomIv>>
> > >  
> > > But you read:
> > >  
> > > Is your data <<IvSpec:8/binary, IV:8/binary, Rest/binary>>
> > >  
> > > Should it not be just:
> > >  
> > > <<IV:8/binary, Rest/binary>>
> > >  
> > > ?
> > >  
> > > Sent from Outlook (http://aka.ms/Ox5hz3)
> > > _____________________________
> > > From: Bogdan Andu < (mailto:)>
> > > Sent: Thursday, November 5, 2015 2:26 p.m.
> > > Subject: [erlang-questions] blowfish cbc mode decrypt
> > > To: Erlang < (mailto:)>
> > >  
> > >  
> > >  
> > > Hi,  
> > >  
> > > I have a stream of data called EncryptedData (with randomiv header specification).  
> > > I want to decrypt  using:  
> > > crypto:block_decrypt(blowfish_cbc, hexstr2bin(Key), IV, Rest).  
> > >  
> > > where:  
> > >  
> > > EncryptedData is formatted as follows:  
> > > <<IvSpec:8/binary, IV:8/binary, Rest/binary>>  
> > >  
> > > IvSpec == <<"RandomIV">>  
> > >  
> > > However the decryption does not works and garbage is generated  
> > > (the function  ) .  
> > >  
> > > What could be done given the fact that IV is an 8-byte quantity  
> > > the Key is formatted according to crypto test suites and is 16 bytes long  
> > >  
> > > Am I missing something?  
> > >  
> > > Thanks,  
> > >  
> > > Bogdan  
> > >  
> > >  
> >  
>  

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