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

Thank you Wil, Just been studying the example code in the link you kindly provided. I notice though, that these examples encrypt the entire file in memory before calling 'EVP_CipherFinal_ex( ... )'. My understanding is that without calling this function, decryption of the file will fail. I not sure how compatible this would be with a boost.Iostream filter, which will write the encrypted data on the fly? I guess I could just place the data into a memory buffer, and calling EVP_CypherFinal_ex then writing the data when close is called, but this feels like an ugly solution, that would break the expected operation of an iostream. On Wed, 2012-08-08 at 13:29 -0500, Will Mason wrote:

Hello,

On Wed, Aug 8, 2012 at 1:10 PM, exocoder wrote: Thank you for the info Neil, I am looking at the example that you pointed to, need to get my head around the issues of initialising/closing OpenSSL in the filter. It seems that every OpenSSL example uses a different interface :(

I think the OpenSSL EVP interface is the one you want: http://www.openssl.org/docs/crypto/EVP_EncryptInit.html#

Cheers, Will

Again Thank you for the advice.

On Mon, 2012-08-06 at 15:40 -0600, Neil Nelson wrote: > 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... > > 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. > > _______________________________________________ > Boost-users mailing list > Boost-users@lists.boost.org > http://lists.boost.org/mailman/listinfo.cgi/boost-users

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