Yes, I agree with you.
The message that I want to cypher, is not a real message. I want to cypher a
struct with two fields:
- A symmetric key, and
- A integer with a special meaning for my application.
And this struct have a size bigger than RSA key size, and I need use blocks.
And, I think that it is a correct use of the RSA cypher/decypher method,
isn�t you?.
Regards.
----- Original Message -----
From: "Eduardo P�rez" <[EMAIL PROTECTED]>
To: <[email protected]>
Sent: Monday, May 16, 2005 10:40 AM
Subject: Re: Problem at RSA decrypt: block type is not 02
> What are you trying to do?
> (give some details if you want any help)
>
> Using RSA directly on the message is almost never a good idea.
> (Correct me if I'm wrong but that's what you seem to be doing)
> You should be using an intermediate symmetric cipher or just let openssl
> or gnupg do its job and forget about the internal specifics of key
> selection and protocol.
>
> Eduardo
>
> On 2005-05-16 07:21:25 UTC, Angel Martinez Gonzalez wrote:
> > I want to cypher/decrypt messages with RSA.
> >
> > I use this functions to cypher and decypher:
> >
> > int CifradoClavePublica(RSA *claveRSA, char *texto, char **textocifrado)
> > {
> > int size = RSA_size(claveRSA);
> > int blksize = size - 12;
> > int length = strlen(texto);
> > int blocks = length/blksize;
> > int rest = length%blksize;
> >
> > int i;
> > int tamano_datos_cifrados;
> > int longitud_datos_cifrados = 0;
> >
> > if (rest == 0)
> > *textocifrado = malloc(blocks*size+1);
> > else
> > *textocifrado = malloc((blocks+1)*size+1);
> >
> >
> > for (i=0; i<blocks; i++)
> > {
> > tamano_datos_cifrados = RSA_public_encrypt(blksize, texto+i*blksize,
> > *textocifrado+i*size, claveRSA, RSA_PKCS1_PADDING);
> > longitud_datos_cifrados = longitud_datos_cifrados +
tamano_datos_cifrados;
> > }
> >
> > if (rest != 0)
> > {
> > tamano_datos_cifrados = RSA_public_encrypt(rest, texto+blocks*blksize,
> > *textocifrado+blocks*size, claveRSA, RSA_PKCS1_PADDING);
> > longitud_datos_cifrados = longitud_datos_cifrados +
tamano_datos_cifrados;
> > }
> >
> > return (longitud_datos_cifrados);
> >
> > }
> >
> > This function returns the size of the encrypted data. "claveRSA" is the
> > public key RSA, "texto" is the message to cypher, and "textocifrado"
stores
> > the ciphertext.
> >
> >
> > To decypher, I use this function:
> >
> > char *DescifradoClavePrivada(RSA *claveRSA, char *texto, int
> > longitud_datos_cifrados)
> > {
> > int size = RSA_size(claveRSA);
> > int blksize = size-12;
> > int length = longitud_datos_cifrados;
> > int blocks = length/size;
> >
> > int i, error;
> > int written = 0;
> > char *textoclaro;
> > int tamano_datos_descifrados;
> >
> > char *fileError = "error.txt";
> >
> > FILE *fp;
> >
> > textoclaro = malloc(blocks*blksize+1);
> >
> > for (i=0; i<blocks; i++)
> > {
> > printf ("bucle %i\n",i);
> > tamano_datos_descifrados = RSA_private_decrypt(blksize, texto+i*size,
> > textoclaro+written, claveRSA, RSA_PKCS1_PADDING);
> >
> >
> > ERR_load_crypto_strings();
> > error = ERR_get_error();
> > printf ("Library: %s\n", ERR_lib_error_string(error));
> > printf ("Function: %s\n", ERR_func_error_string(error));
> > printf ("Reason: %s\n", ERR_reason_error_string(error));
> >
> > written = written + tamano_datos_descifrados;
> > }
> > return (textoclaro);
> >
> > }
> >
> > This function returns the plain text. "claveRSA" is the private key RSA,
> > "texto" is the cyphertext to decrypt, and "longitud_datos_cifrados" is
the
> > size of the encrypted data "texto".
> >
> > And when I run this function, I obtain this error message:
> >
> > Library: rsa routines
> > Function: RSA_padding_check_PKCS1_type_2
> > Reason: block type is not 02
> >
> > What meaning this error?, What it is wrong?. Thanks.
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