Re: [Boost-users] boost.Iostream OpenSSL Filter

Subject: Re: [Boost-users] boost.Iostream OpenSSL Filter
From: Neil Nelson (nnelson_at_[hidden])
Date: 2012-08-06 17:40:33

exocoder,

Upon just reading the docs at

http://www.boost.org/doc/libs/1_50_0/libs/iostreams/doc/index.html

and particularly

     2.2.8. Multi-Character Filters

It looks like you could take the code from the following page

http://stackoverflow.com/questions/1007337/encrypting-and-decrypting-a-small-file-using-openssl

with the critical line being

     AES_cfb128_encrypt(indata, outdata, bytes_read, &key, ivec, &num, 
AES_ENCRYPT);

that reads and writes to memory buffers. Two other aspects are: (1) 
software using encryption is export restricted and you can research that 
if needed for your application, (2) key management is likely the more 
complicated part, and (3) use of initialization vectors (added random 
bytes at the beginning of the input data).

Neil Nelson

> I am currently looking at using OpenSSL to write information to an
> encrypted file on-the-fly so to speak. I have been researching my
> options for doing this, and have come across the Boost.Iostream library,
> which promises to be a very elegant solution (The documentation even
> suggests that filters can be written to provide encryption/decryption
> using OpenSSL).
> It would seem that my best approach would be to use the BIO_f* interface
> to encrypt a memory buffer, which could be written by overloading
> write(). However the OpenSSL documentation is particularly sparse when
> it comes to file/memory encryption and I would appreciate any advice on
> how to do this.
> Thank you in advance for any help proffered.