On Mon, Aug 10, 2009, MusicAndy wrote:
>
> OK, so after the last post I made; I was trying to use the DES library, and
> was advised to use the higher level EVP library, I have now used this and
> getting the same type of error! %-|
>
> So where do I go from here. The command line that i wish to use for
> decrypting the file that i am encrypting is
> openssl des3 -d -nosalt -k "1" -in <source filename> -out <destination
> filename>
>
> The code that i am using to test these has two file streams, one for the
> input and one for the output and is shown below. This is test code only.
> What am i doing wrong here? Is it the key that is at fault. Please help...
> I also wish to use salt in the final implementation on this. Please
> advise...
>
>
> if(infile == NULL)
> AfxMessageBox("File load error");
>
> fseek(infile, 0L, SEEK_END);
> numbytes = ftell(infile);
>
> fseek(infile, 0L, SEEK_SET);
>
> buffer = (char*)calloc(numbytes, sizeof(char));
>
> fread(buffer, sizeof(char), numbytes, infile);
>
>
> unsigned char* input = new unsigned char[numbytes];
> input = (unsigned char*)buffer;
>
>
> if(buffer == NULL)
> AfxMessageBox("Error with buffer");
>
> unsigned char password[] = {'1'};
> EVP_CIPHER_CTX ctx;
> EVP_CIPHER_CTX_init(&ctx);
>
> unsigned char* desBuf = new unsigned char[numbytes];
>
> EVP_EncryptInit_ex(&ctx, EVP_des_ede3_cbc(), NULL,password,NULL);
>
Well that's the problem right there. You have to pass a key and IV of the
correct length to EVP_EncryptInit_ex(). You are passing 1 byte and whatever
garbage follows it in memory.
You need to derive the correct key using EVP_BytestToKey() and pass the
derived key to EVP_EncryptInit_ex().
Steve.
--
Dr Stephen N. Henson. OpenSSL project core developer.
Commercial tech support now available see: http://www.openssl.org
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