+ const size_t field_size = EC_field_size(EC_KEY_get0_group(key));
+ const int md_size = EVP_MD_size(digest);
+ size_t overhead;
+
+ if (md_size < 0) {
+ SM2err(SM2_F_SM2_PLAINTEXT_SIZE, SM2_R_INVALID_DIGEST);
+ return 0;
+ }
+ if (field_size == 0) {
+ SM2err(SM2_F_SM2_PLAINTEXT_SIZE, SM2_R_INVALID_FIELD);
+ return 0;
+ }
+
+ overhead = 10 + 2 * field_size + (size_t)md_size;
+ if (msg_len <= overhead) {
+ SM2err(SM2_F_SM2_PLAINTEXT_SIZE, SM2_R_INVALID_ENCODING);
+ return 0;
+ }
+
+ *pt_size = msg_len - overhead;
+ return 1;
+}
+
+int SM2_ciphertext_size(const EC_KEY *key, const EVP_MD *digest, size_t msg_len,
+ size_t *ct_size)
+{
+ const size_t field_size = EC_field_size(EC_KEY_get0_group(key));
+ const int md_size = EVP_MD_size(digest);
+
+ if (field_size == 0 || md_size < 0)
+ return 0;
+
+ *ct_size = 10 + 2 * field_size + (size_t)md_size + msg_len;
+ return 1;