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ASCII->POLY: use double base64 encoding for more entropy

This commit is contained in:
hasufell 2014-05-28 02:04:45 +02:00
parent 51c6537777
commit bf192a0498
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GPG Key ID: 220CD1C5BDEED020
2 changed files with 77 additions and 17 deletions
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77
src/ascii_poly.c
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@ -280,22 +280,56 @@ bin_poly_arr_to_ascii(fmpz_poly_t **bin_poly_arr, ntru_context *ctx)
/*------------------------------------------------------------------------*/
string *
poly_to_ascii(fmpz_poly_t poly,
ntru_context *ctx)
{
string *result_string = ntru_malloc(sizeof(*result_string));
char *string_rep = ntru_malloc(CHAR_SIZE * (ctx->N));
uint32_t i = 0;
for (uint32_t j = 0; j < ctx->N; j++) {
uint8_t coeff = fmpz_poly_get_coeff_ui(poly, j);
if (coeff == ctx->q)
string_rep[i] = '\0';
else
string_rep[i] = (char)coeff;
i++;
}
result_string->ptr = string_rep;
result_string->len = i;
return result_string;
}
/*------------------------------------------------------------------------*/
fmpz_poly_t **
base64_to_poly_arr(string *to_poly, ntru_context *ctx)
{
uint32_t i = 0,
polyc = 0;
gsize out_len;
guchar *base64_decoded;
guchar *base64_decoded = NULL,
*base_tmp = NULL;
string *new_string = ntru_malloc(sizeof(*new_string));
fmpz_poly_t **poly_array;
char tmp[to_poly->len + 1];
char *tmp = ntru_malloc(sizeof(char) * (to_poly->len + 1));
/* g_base64_decode() needs it null-terminated */
memcpy(tmp, to_poly->ptr, to_poly->len);
tmp[to_poly->len] = '\0';
base_tmp = g_base64_decode((const gchar *)tmp, &out_len);
/* g_base64_decode() needs it null-terminated */
REALLOC(tmp, sizeof(char) * (out_len + 1));
memcpy(tmp, base_tmp, out_len);
tmp[out_len] = '\0';
base64_decoded = g_base64_decode((const gchar *)tmp, &out_len);
new_string->ptr = (char *)base64_decoded;
new_string->len = (unsigned long)(out_len);
@ -331,6 +365,8 @@ base64_to_poly_arr(string *to_poly, ntru_context *ctx)
poly_array[polyc] = NULL;
string_delete(new_string);
free(base_tmp);
free(tmp);
return poly_array;
}
@ -342,25 +378,23 @@ poly_to_base64(fmpz_poly_t poly,
ntru_context *ctx)
{
string *result_string = ntru_malloc(sizeof(*result_string));
char *string_rep = ntru_malloc(CHAR_SIZE * (ctx->N));
uint32_t i = 0;
gchar *base64_string = NULL;
string *string_rep = NULL;
gchar *base64_string = NULL,
*tmp = NULL;
for (uint32_t j = 0; j < ctx->N; j++) {
uint8_t coeff = fmpz_poly_get_coeff_ui(poly, j);
if (coeff == ctx->q)
string_rep[i] = '\0';
else
string_rep[i] = (char)coeff;
i++;
}
string_rep = poly_to_ascii(poly, ctx);
base64_string = g_base64_encode((const guchar *)string_rep, i);
tmp = g_base64_encode((const guchar *)string_rep->ptr,
string_rep->len);
base64_string = g_base64_encode((const guchar *)tmp,
strlen(tmp));
result_string->ptr = base64_string;
result_string->len = strlen(base64_string);
free(string_rep);
free(tmp);
return result_string;
}
@ -377,6 +411,8 @@ poly_arr_to_base64(fmpz_poly_t **poly_array,
string *result_string = ntru_malloc(sizeof(*result_string));
size_t old_length = 0,
new_length;
gchar *base64_string = NULL,
*tmp = NULL;
/*
* parse the polynomial coefficients into a string
@ -385,7 +421,7 @@ poly_arr_to_base64(fmpz_poly_t **poly_array,
while ((ascii_poly = *poly_array++)) {
string *poly_str;
poly_str = poly_to_base64(*ascii_poly, ctx);
poly_str = poly_to_ascii(*ascii_poly, ctx);
new_length = CHAR_SIZE * poly_str->len;
REALLOC(string_rep,
@ -401,8 +437,15 @@ poly_arr_to_base64(fmpz_poly_t **poly_array,
string_delete(poly_str);
}
result_string->ptr = string_rep;
result_string->len = string_len;
tmp = g_base64_encode((const guchar *)string_rep, string_len);
base64_string = g_base64_encode((const guchar *)tmp,
strlen(tmp));
result_string->ptr = base64_string;
result_string->len = strlen(base64_string);
free(string_rep);
free(tmp);
return result_string;
}

17
src/ascii_poly.h
View File

@ -120,6 +120,23 @@ bin_poly_to_ascii(fmpz_poly_t poly,
string *
bin_poly_arr_to_ascii(fmpz_poly_t **bin_poly_arr, ntru_context *ctx);
/**
* Convert a single polynom back to a real string which is
* ascii encoded (full 256 C char spectrum).
* The polynomial coefficients are expected to be in the range
* [0, q-1] and will be casted back to chars without any mapping.
*
* Trailing q coefficients are only used for filling up the rest of
* a polynomial with '\0', so they will not confuse the result.
*
* @param poly the polynomial to convert
* @param ctx the NTRUEncrypt context
* @return the real string, newly allocated
*/
string *
poly_to_ascii(fmpz_poly_t poly,
ntru_context *ctx);
/**
* Convert an base64 encoded string to an array of polyomials with
* coefficients which are expected to be in the range [0, q-1].