Removes bias from generating random curve points.

1 files changed, 29 insertions, 27 deletions

diff --git a/libcmix-crypto/ed25519/gcrypt/gcrypt_ed25519.c b/libcmix-crypto/ed25519/gcrypt/gcrypt_ed25519.c
index c8913cf..bcaca51 100644
--- a/libcmix-crypto/ed25519/gcrypt/gcrypt_ed25519.c
+++ b/libcmix-crypto/ed25519/gcrypt/gcrypt_ed25519.c
@@ -306,58 +306,60 @@ GroupElement DEF(get_group_element)(bool secure) {
 	(void) secure;
 	size_t parse_error_offset;
 	gcry_error_t error;
-	
+
+	gcry_mpi_point_t point = gcry_mpi_point_new(0);
 	gcry_mpi_t a = NULL;
 	void* bytes = NULL;
+	char* encoded_point = NULL;
 	do {
-		gcry_free(bytes);
-		gcry_mpi_release(a);
-		bytes = gcry_random_bytes_secure(nr_bytes, GCRY_VERY_STRONG_RANDOM);
-		TRACE(__FILE__, __LINE__, bytes);
-		error = gcry_mpi_scan(&a, GCRYMPI_FMT_USG, bytes, nr_bytes, &parse_error_offset);
-		TRACE(__FILE__,__LINE__, a);
-		check(error);
-	} while(gcry_mpi_cmp_ui(a, 0) == 0 || gcry_mpi_cmp(a, p) != -1);
-	
-	char* encoded_point = (char*) calloc(nr_bytes+1, sizeof(char));
-	TRACE(__FILE__, __LINE__, encoded_point)
-	gcry_mpi_point_t point = gcry_mpi_point_new(0);
-	do {
+		do {
+			gcry_free(bytes);
+			gcry_mpi_release(a);
+			bytes = gcry_random_bytes_secure(nr_bytes, GCRY_VERY_STRONG_RANDOM);
+			TRACE(__FILE__, __LINE__, bytes);
+			error = gcry_mpi_scan(&a, GCRYMPI_FMT_USG, bytes, nr_bytes, &parse_error_offset);
+			TRACE(__FILE__,__LINE__, a);
+			check(error);
+		} while(gcry_mpi_cmp_ui(a, 0) == 0 || gcry_mpi_cmp(a, p) != -1);
+
+		char* encoded_point = (char*) calloc(nr_bytes+1, sizeof(char));
+		TRACE(__FILE__, __LINE__, encoded_point)
+
+		free(encoded_point);
+		encoded_point = (char*) calloc(nr_bytes+1, sizeof(char));
 		encoded_point[0] = 0x40;
-		
+
 		unsigned int byte_size = (unsigned) ceil(gcry_mpi_get_nbits(a) / 8.0);
 		gcry_mpi_print(GCRYMPI_FMT_USG, (unsigned char*) encoded_point + 1, 32, NULL, a);
-	
+
 		for(int i = 0; i < 16; i++) {
 			char temp = encoded_point[i+1];
 			encoded_point[i+1] = encoded_point[32-i];
 			encoded_point[32-i] = temp;
 		}
-	
+
 		gcry_mpi_t encoded_mpi = gcry_mpi_new(0);
 		TRACE(__FILE__, __LINE__, encoded_mpi)
 		gcry_mpi_set_opaque_copy(encoded_mpi, encoded_point, (nr_bytes + 1) * sizeof(char) * 8);
-		
+
 		error = gcry_mpi_ec_decode_point(point, encoded_mpi, ctx);
 		check(error);
-			
+
 		gcry_mpi_release(encoded_mpi);
-		
+
 		if(!gcry_mpi_ec_curve_point(point, ctx)) {
 			gcry_mpi_point_release(point);
 			point = gcry_mpi_point_new(0);
-			
-			gcry_mpi_add_ui(a, a, 1);
 		}
-	
+
 	} while(!gcry_mpi_ec_curve_point(point, ctx));
-	
+
 	gcry_mpi_release(a);
 	gcry_free(bytes);
 	free(encoded_point);
-	
+
 	TRACE(__FILE__, __LINE__, point);
-	
+
 	return point;
 }
 
@@ -526,4 +528,4 @@ void DEF(deinitialize)(void) {
 	gcry_ctx_release(ctx);
 }
 
-LINK_IMPLEMENTATION
\ No newline at end of file
+LINK_IMPLEMENTATION