On Fri, May 24, 2002, Brad House wrote:
> Ok, I looked at the openssl documentation stating that
> blowfish accepts a variable key length. But it also says
> to use the EVP method of encryption for Applications because
> it provides a more generic way to use multiple algorithms, etc...
>
> Anyhow, I can't set a different key length for blowfish
> using the EVP routines, this is what I'm doing:
>
>
> char iv[]={ 1, 2, 3, 4, 5, 6, 7, 8 };
>
> int do_crypt(char *source, long src_len, char *target, char *key)
> {
> int outlen, tmplen;
> EVP_CIPHER_CTX ctx;
> EVP_CIPHER_CTX_init(&ctx);
> EVP_EncryptInit(&ctx, EVP_bf_cbc(), key, iv);
> /* let's try to extend the key length used!!!! */
> EVP_CIPHER_CTX_set_key_length(&ctx, 32);
> if (!EVP_EncryptUpdate(&ctx, target, &outlen, source, src_len+1))
> return(0);
> if (!EVP_EncryptFinal(&ctx, target + outlen, &tmplen))
> return(0);
> outlen += tmplen;
> EVP_CIPHER_CTX_cleanup(&ctx);
> return(outlen);
> }
>
>
> But when I comment out the key length line, and truncate the key
> so it's only 16 bytes instead of 32, it returns the same ciphertext.
>
> Is it not possible with EVP to change the key size??
> I've checked the return code of EVP_CIPHER_CTX_set_key_length, and
> everything looks like it should be working ...
>
> I'm using OpenSSL 0.9.6b
>
You need two calls to EVP_EncryptInit if you are changing cipher
parameters, check the manual pages for more info.
Steve.
--
Dr. Stephen Henson [EMAIL PROTECTED]
OpenSSL Project http://www.openssl.org/~steve/
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