Hi,
I would be grateful if you could expand on this. I've tried simply placing
the bit length for the AES_set_encrypt_key call and it still produces the
same result.
Thanks,
Anantha
On Tue, Nov 1, 2011 at 8:10 PM, re est <re.est1...@gmail.com> wrote:
> Hi,
>
> I have tried your code and replaced the length param with bit length
> (*8) instead.
> It worked. It seems that there are inconsistent with the usage of API.
>
> - re.est
>
> On Sun, Oct 30, 2011 at 4:55 PM, Ananthasayanan Kandiah
> <ananthasaya...@obtino.com> wrote:
> > Hi,
> >
> > I'm trying to use AES-CFB1 through the "low-level" calls. Here's the
> example
> > program I have come up with:
> >
> > #include <stdio.h>
> > #include <string.h>
> > #include <openssl/aes.h>
> > #include <openssl/bio.h>
> >
> > #define KEY_SIZE 16
> >
> > int main(void)
> > {
> > int i;
> > AES_KEY key;
> > BIO* bio_out;
> >
> > unsigned char key_data[KEY_SIZE] = {
> > 0xfe, 0xec, 0x82, 0x17, 0xb5, 0x1, 0x98, 0x6b,
> > 0x5e, 0xf1, 0xb8, 0x6, 0x52, 0x74, 0x2e, 0x52
> > };
> >
> > unsigned char iv[AES_BLOCK_SIZE];
> >
> > unsigned char const iv_data[AES_BLOCK_SIZE] = {
> > 0x10, 0x8a, 0xc9, 0x30, 0xb7, 0xf2, 0x35, 0x21,
> > 0xfb, 0xac, 0x6b, 0xdf, 0x80, 0x95, 0xeb, 0x1e
> > };
> >
> > char* data = "Internet is a wonderful mechanism for making a
> fool "
> > "of yourself in front of a very large audience";
> >
> >
> > int length = (int) strlen(data);
> >
> > int num = 0;
> >
> > /* Allocate some space for the ciphertext and plaintext */
> > char* ciphertext = (char*) malloc(sizeof(char) * length);
> > char* plaintext = (char*) malloc(sizeof(char) * length);
> >
> > /* Copy the IV data to the IV array */
> > memcpy(iv, iv_data, AES_BLOCK_SIZE);
> >
> > /* Set the encrypt key structure using the predefined key */
> > AES_set_encrypt_key(key_data, KEY_SIZE * 8, &key);
> >
> > /* Carry out the encryption */
> > AES_cfb1_encrypt(data, ciphertext, length, &key, iv, &num,
> AES_ENCRYPT);
> >
> > /* Setup output */
> > bio_out = BIO_new_fp(stdout, BIO_NOCLOSE);
> >
> > BIO_printf(bio_out, "Original plaintext: %s\n\n", data);
> >
> > BIO_printf(bio_out, "Ciphertext: ");
> >
> > /* Print out the ciphertext */
> > for (i = 0; i < length; i++)
> > BIO_printf(bio_out, "%02x", ((unsigned char*)ciphertext)[i]);
> >
> > BIO_printf(bio_out, "\n\n");
> >
> > /* Start the decryption process */
> >
> > /* First, copy the original IV data back to the IV array - as it was
> > overwritten
> > * during the encryption process
> > */
> > memcpy(iv, iv_data, AES_BLOCK_SIZE);
> >
> > /* Reset how far we've gone through the IV */
> > num = 0;
> >
> > /* Carry out the decryption */
> > AES_cfb1_encrypt(ciphertext, plaintext, length, &key, iv, &num,
> > AES_DECRYPT);
> >
> > BIO_printf(bio_out, "Recovered plaintext: ");
> >
> > /* print out the plaintext */
> > for (i = 0; i < length; i++)
> > BIO_printf(bio_out, "%c", ((unsigned char*)plaintext)[i]);
> >
> > BIO_printf(bio_out, "\n\n");
> >
> > BIO_free(bio_out);
> >
> > free(ciphertext);
> > free(plaintext);
> >
> >
> > return 0;
> > }
> >
> > When I run it, the output which I receive is:
> >
> > Original plaintext: Internet is a wonderful mechanism for making a foolof
> > yourself in front of a very large audience
> >
> > Ciphertext:
> >
> 92c0883c54eb8df072b43278000000000000000000000000000000000000000000000000000000000000000000000000000000000000
> >
> 000000000000000000000000000000000000000000000000000000000000000000000000000000000000
> >
> > Recovered plaintext: Internet is
> >
> >
> >
> d:\ananthasayanan\stuff\projects\programming\openssl\openssl-1.0.0d\demos\crypto\low_level\ciphers\symmetric\aes\aes_cfb
> > 1_128\x64\Release>aes_cfb1_128.exe
> > Original plaintext: Internet is a wonderful mechanism for making a fool
> of
> > yourself in front of a very large audience
> >
> > Ciphertext:
> >
> 92c0883c54eb8df072b43278000000000000000000000000000000000000000000000000000000000000000000000000000000000000
> >
> 00000000000000000000000000000000000000000000000000000000000000000000000000000000000000
> >
> > Recovered plaintext: Internet is
> >
> > As you can see, the ciphertext that is produced is only 12 bytes in
> length.
> > Hence, the recovered plaintext has only 12 characters. I have had a look
> at
> > the source-code for AES_cfb1_encrypt and the comment says that the input
> > should be "packed". What does this mean? Am I doing something wrong or is
> > there a bug with AES-CFB1?
> >
> >
> > Thanks,
> > Anantha
> >
> >
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